Lymphatic System And Immunity Chapter 13

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lymphatic system consists of

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lymph, lymphatic vessels, lymphatic tissue, lymphatic nodules, lymphatic nodes, tonsils, spleen, thymus

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functions of the lymphatic system

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fluid balance, fat absorption, defense

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fluid balance

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function of lymphatic system; excess interstitial fluid enters lymphatic capillaries and becomes lymph, ~3L of fluid in lymphatic capillaries

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fat absorption

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function of lymphatic system; absorption of fat from digestive tract via lacteals; lacteas lead into lymphatic vessels to venous circulation

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defense

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function of lymphatic system; lymph nodes constantly filter microorganisms and foreign substances from the lymph; the spleen filters these substances from the blood

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lymph

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returns to circulatory system via veins; maintains fluid balance in the body; excess interstitial fluid passes into lymphatic vessels and enters lymph

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composition of lymph

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composed of water plus solutes from 2 sources; blood plasma - ions, nutrients, gases and some proteins; cells - hormones, enzymes and cellular waste products

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lymphatic vessels

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carry lymph away from tissues

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lymphatic capillaries

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more permeable than blood capillaries; nothing is excluded from entering; have a one-way series of valves that ensures lymph only flows in one direction

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lymphatic capillaries are found in all tissues of the body except

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nervous system, bone marrow, tissues without blood supply (cartilage, epithelial tissue and cornea)

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types of lymphatic vessels

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lymphatic capillaries, lymphatic vessels, lymph nodes, lymphatic trunks, lymphatic ducts

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lymphatic capillaries

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join to form lymphatic vessels

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lymphatic vessels

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look like small veins, have one-way valves

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lymph nodes

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structures that are distributed along vessels; filter lymph as it moves through

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lymphatic trunk

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convergence of lymphatic vessels to form a large vessel; each drains a major portion of the body

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5 lymphatic trunks

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jugular; subclavian; bronchomediastinal; intestinal; lumbar

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lymphatic ducts

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convergence of lymphatic trunks; drains the tissues of the body and move lymph into major veins; lymph enters circulatory system here; right lymphatic ducts and thoracic ducts

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right lymphatic ducts

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drains right side of head, right arm and right thorax

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thoracic duct

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drains remainder of body

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jugular

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drains head and neck

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subclavian

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drains upper limbs, superficial throacic wall and mammary glands

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bronchomediastinal

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drains thoracic organs and deep thoracic wall

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intestinal

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drains intestines, stomach, pancreas, spleen, liver

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lumbar

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drains lower limbs, pelvic and abdominal walls, ovaries, testes, kidneys and adrenal gland

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lymphatic tissue and organs

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lymphatic organs contain lymphatic tissue (mainly lymphocytes, also macrophages, dendritic cells and reticular cells); fine collagen reticular fibers; may be encapsulated by connective tissue

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lymphocytes

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WBCs that originate in the bone marrow

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fine collagen reticular fibers

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produced by reticular cells; acts as a filter to trap microorganisms and other substances

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encapsulated

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lymph nodes, spleen, thymus

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unencapsulated

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mucosa-associated lymphoid tissue (MALT); found beneath epithelium; 1st line of defense against invaders; found in mucous membrane lining digestive, urinary, respiratory and reproductive tracts

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diffuse lymphatic tissue

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made up of dispersed lymphocytes and macrophages; blends in with the other tissues and is associated with other types of lymphatic tissue (lymphatic nodules in lymphatic nodes and spleen)

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lymphatic nodules

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dense grouping of lymphatic tissue; loose connective tissue in digestive system called Peyer's patches; found as MALT in urinary, respiratory and reproductive system; referred to as lymphatic follicles when found in lymph nodes and the spleen

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tonsils

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large groups of lymphatic nodules; located in nasopharynx; protect against bacteria and other foreign substances; palatine, pharyngeal, lingual tonsils

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palatine tonsils

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"the tonsils"

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pharyngeal tonsils

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adenoids

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lymph nodes

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found on superficial (near skin) and deep; small (1-25mm long); round or bean shaped; only structures that filter lymph and remove bacteria or other substances; substances removed by phagocytosis; afferent and efferent lymphatic vessels; cancer cells often migrate to lymph nodes and get trapped there

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substances removed by phagocytosis in lymph nodes

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the substances may stimulate lymphocyte proliferation (increase in numbers)

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cancer cells migrate to lymph nodes and get trapped there

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cancer cells proliferate there; can move through lymphatic system to circulatory system and then enter other tissues

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location of spleen

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left superior side of abdomen

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spleen rupture

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can rupture with traumatic abdominal injury; causes bleeding, shock and death; removal of spleen and other lymphatic tissues will compensate for it

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spleen composed of

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white pulp around arteries; red pulp around veins; lymphatic nodules contain lymphocytes and macrophages

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blood flows through spleen at 3 different rates

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fast - most of blood takes a few seconds; slow - 2% of blood takes an hour or more; intermediate - 10% of blood takes a few minutes

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functions of spleen

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destroys defective RBCs; detects and responds to foreign substances; limited reservoir for blood

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spleen is reservoir for blood

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during exercise, spleen volume decreases 40-50% of blood as blood enters circulatory system

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thymus location

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in superior area of mediastinum; grows really fast during 1st year of life and stays the same size throughout adulthood and size decreases after 60 years old

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composition of thymus

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no reticular fibers; cortex - numerous lymphocytes; medulla - fewer lymphocytes

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T cells in thymus

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thymus is site of T cell maturation (a type of lymphocyte); a lot of T cells are produced in thymus gland, but nost do not survive; remaining T cells are capable of reacting to a foreign substance, but not to healthy body tissue (self); surviving T cells enter circulatory system and travel to other lymphatic tissues

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definition of immunity

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the ability to resist damage from foreign substances, microorganisms, chemicals

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2 categories of immunity

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innate and adaptive

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innate immunity

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nonspecific resistance; the body recognizes and destroys certain foreign substances, response is always the same

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adaptive immunity

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specific immunity; the body recognizes and destroys certain foreign substances, response improves every time; specificity and memory

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specificity

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adaptive immunity; ability of immune cells to recognize a substance

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memory

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adaptive immunity; ability of immune cells to "remember" previous encounters with a substance and respond rapidly

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mechanical mechanisms of innate immunity

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prevent entry or remove microbes; involves skin, tears, saliva, mucous membranes, mucous, urine = all of these are considered the acid mantle

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types of mechanisms of innate immunity

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skin and mucous membranes prevent entry; tears, saliva and urine flush out microbes; cilia, coughing and sneezing remove microbes

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chemical mediators of innate immunity

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promote phagocytosis and inflammation; lysozymes, sebum and mucous prevent foreign substnace entry; histamines, complement and other chemicals promote inflammation and attract WBCs

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complement

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a group of 20 plasma proteins (globulins); circulatein the blood in their inactive form; include proteins C1-C9 and factors B, D and P; they become activated during a complement cascade activation reaction; classical or alternative pathway

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alternative pathway of complement

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part of the innate immunity response; complement protein C3 binds to a foreign substance and also binds with factors B, D and P; this activates proteins C5-C9; proteins C3-C9 promote phagocytosis and attract macrophages to the area

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classical pathway of complement

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part of adaptive immunity; begins with activation of C1; requires antibodies to be bound to antigens

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activated complement proteins can

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form membrane attack complexes (MACs); MACs form a channel through plasma membrane to a foreign cell; allows water and Na+ to enter into cell and cell lyses; can attach to surface of bacteria cells; stimulates phagocytosis by macrophages; attracts WBCs to that area to promote inflammation

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interferons

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prevent viral replication; viruses insert themselves into host DNA and use the host cell to replicate themselves; cells typically die during replication process; viruses also stimulate the host cell to produce interferons; interferons produced in an infected cell cannot save that cell; but they stimulate neighboring cells to produce antiviral proteins and prevent viral replication

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innate immunity cells

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WBCs, neutrophils, macrophages, basophils and mast cells, eosinophils, natural killer cells

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white blood cells in innate immunity

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innate immunity; most important cellular components of the immune system; have to be able to move into infected tissue and destroy that infection; chemotaxis - chemicals from foreign substances, infected cells and other WBCs can attract more WBCs to the area; phagocytosis - endocytosis by macrophages and neutrophils

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chemotaxis

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innate immunity; movement toward source of a chemical

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neutrophils

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innate immunity; phagocytic; 1st cells to enter infected tissue

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macrophages

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innate immunity; large phagocytic cells; monocytes that leave the circulatory system and enter tissues; live longer than neutrophils; can phagocytize larger substances than neutrophils

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basophils and mast cells

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innate immunity; produce inflammatory response; leave circulatory system and enter into infected tissues; mast cells do not stay in the circulatory system, they leave and reside in connective tissue to wait for infection; basophils and mast cells release histamine and heparin

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eosinophils

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innate immunity; leave blood and enter into tissues; reduce inflammation by breaking down histamine; secretes enzymes to kill some parasites

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natural killer cells

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innate immunity; types of lymphocyte (15% of lymphocytes); lyse tumor and viral infected cells (not specific)

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inflammatory response

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any type of tissue injury can cause inflammation; response initiated by chemical mediators that produce vasodilation, vascular permeability and chemotactic attraction; increased vascular permeability allows fibrinogen and complement to enter tissue; fibrinogen converts fibrin and walls off infected area

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types of inflammatory response

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local and systemic

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local inflammatory response

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confined to a specific area of the body

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symptoms of local inflammatory response

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redness, heat, swelling = due to increased blood flow; pain = due to swelling and chemical release; loss of function = due to tissue damage, swelling and pain

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systemic inflammatory response

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occurs in many parts of the body

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symptoms of systemic inflammatory response

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redness, heat, swelling = due to increased blood flow; pain = due to swelling and chemical release; loss of function = due to tissue damage, swelling and pain; increase in neutrophil numbers; fever produced = due to chemicals called pyrogens; widespread vascular permeability = due to histamine release; large volume of plasma to enter tissue interstitial spaces; can cause shock and may lead to death

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pyrogens

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in systemic inflammatory response; produces fever; produced by various cells; improve immune system function; they conserve heat, promote phagocytosis and destroy some microorganisms

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adaptive immunity

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involves the ability to recognize, remember and respond to a particular substance

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antigens

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large molecules that stimulate immune response; 2 types - foreign and self-antigens

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foreign antigens

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adaptive immunity; not produced by your body, introduced from outside; disease causing antigens - bacteria, viruses, microorganisms; allergic reaction causing antigens - pollen, animal dander, mite feces, foods, drugs

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self-antigens

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adaptive immunity; produced by the body; used as markers by immune system to identify self from non-self; helpful - respond to self tumor antigens; harmful - tissue destruction when immune system responds to self antigens (autoimmune disease)

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haptens

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adaptive immunity; very small molecules that combine with large proteins and produce an adaptive immune response

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example of hapten in adaptive immunity

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penicillin - small molecule; binds with large plasma proteins and produces an allergic response in some people

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types of adaptive immunity

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humoral or antibody-mediated - involves lymphocytes called B cells; involves lymphocytes called T cells

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cells mediated in adaptive immunity

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B cells and T cells

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B cells

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adaptive immunity; produce antibodies in plasma that protect it from extracellular antigens

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T cells

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adaptive immunity; protect against intracellular antigens; 2 classes - effector T cells and delayed hypersensitivity T cells

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effector T cells

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adaptive immunity; cytotoxic T cells

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delayed hypersensitivity T cells

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adaptive immunity; promote or inhibit antibody or cell mediated response

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origin and development B and T cells

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originate in red bone marrow as immature cells; B cells remain in red bone marrow to mature; T cells migrate and mature in thymus gland

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positive selection

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ensures that only lymphocytes that react against antigens survive; these will proliferate and form identical clones; cells that do not respond to antigens die; each individual type of clone only responds to a specific antigen; but many, many, many different types of clones

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negative selection

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eliminates clones that react against self-antigens; mainly occurs during fetal development but also occurs throughout life; tolerance

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tolerance

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in negative selection; the unresponsiveness of a lymphocyte to a specific antigen; usually tolerance to self-antigens

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activation of lymphocytes

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lymphocytes have to be able to recognize an antigen; after recognition, lymphocytes have to increase in number to destroy antigen; antigenic determanants

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antigenic determinants

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activation of lymphocytes; epitopes; a specific region on an antigen that is recognized by a lymphocyte; each antigen has several epitopes

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activation of lymphocytes can occur in 2 ways

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antigenic receptors and MHC molecules

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antigenic receptors

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activation of lymphocytes; T cell receptors and B cell receptors; a receptor on T cell/B cell surface that binds with an epitope; the receptor is specific for a particular epitope

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MHC molecules

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activation of lymphocytes; activate molecules called Major Histocompatability Complex; they attach to plasma membrane; have variable regions that can bind to foreign and self-antigens

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Major Histocompatability Complex

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MHC; MHC class I and class II molecules

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MHC class I molecules

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found on cell surface; works with antigens produced inside cell; MHC I binds to virus particles and moves to cell membrane; displays flag to lymphocytes "im infected, kill me"; once on surface, the complex can bind to T cell receptors and activate a response

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MHC class II molecules

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found on surface of antigen presenting cells (mainly B cells, macrophages, monocytes); antigens are ingested and then combine with MHC II; MHC II and antigen move to cel membrane surface to display and T cells can bind to it; cell is not destroyed; the display of MHC II with foreign antigen stimulates other immune cells to respond to antigen

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costimulation

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in order for B or T cells to produce a response, there must be binding of MHC II/antigen to a T cell receptor and costimulation; chemicals called cytokines are released by macrophages and bind to receptors on the helper T cell; by surface molecules; if costimulation does not occue, they cell exhibits anergy; this is normal response to a self-antigen

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costimulation by surface molecules

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binding of 2 molecules - B7 on macrophages and CD28 on T cell; holds the cell together; CD4 on T cell binds to MHC II on macrophage

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anergy

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no activity; B or T cell will not respond to an antigen without costimulation

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proliferation of lymphocytes

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macrophages process and display antigens on cell surface; antigen bound to MHC II on macrophage surface - this will allow helper T cell to recognize the antigen; costimulation by binding of CD4 to macrophage or cytokine release from macrophage - the macrophage will release the cytokine interleukin 1; interleukin 1 binds to receptor on helper T cell - this stimulates heper T cell to release interleukin 2 and produce interleukin 2 on receptors on its surface; interleukin 2 binds to receptors on helper T cell - this stimulates heper T cell to divide; daughter helper T cells can divide again if exposed to same antigen - this increases helper T cell number; daughter helper T cells can also stimulate effector T cells or B cells

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proliferation of B cells

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B cell must phagocytize the same antigen that activated helper T cell before the B cell can be activated by the helper T cell; B cell processes and presents antigen on cell surface using an MHC II molecule - for helper T cell recognition; helper T cell binds to MHC II antigen complex; B cell costimulation by binding of helper T cell CD4; helper T cell also releases cytokines for costimulation of B cell; B cell divided and daughter B cells divide resulting in many B cell clones; daughter B cells produce antibodies that respond to antigens - produce antibody mediated immune response

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lymphocyte inhibition

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tolerance - unresponsiveness of a lymphocyte to an antigen; most common - unresponsiveness to self-antigens; promoted by destruction of self-reactive lymphocytes, prevention of lymphocyte activation that encounter self-antigen, and activation of suppressor T cells - suppress cytokine release and destroy self-antigen presenting cells

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antibody-mediated immunity

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effective against extracellular antigens including bacteria, virises, protozoans, fungi, parasites and toxins when they are outside cells; antibodies or Immunoglobulins (Ig)

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antibodies or Immunoglobulins

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IgG, IgM, IgA, IgE, IgD

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structure of antibodies (Ig)

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variable region - binds with antigen epitope; constant region - responsible for antibody activities like activation complement, attaching to WBCs; constant region is the same for a class of antibodies

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actions of antibodies

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have 2 ways that they can affect antigens; once an antibody binds to an antigen, other mechanisms are usually activated

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2 ways that antibodies can affect antigens

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antibody can bind to and inactivate an antigen; can bind to 2 antigens and cause them to clump

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action of IgG or IgM

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when bound to an antigen, can activate classical pathway of complement cascade

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action of IgE

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when it binds to an antigen, can attach to mast cells or basophils and initiates the inflammatory response

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action of IgG

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when it binds to an antigen, it can act as an opsonin (substance that promotes phagocytosis); binds to antigen and a macrophage will phagocytize the antibody and antigen

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antibody production

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primary response, secondary response, cell-mediated immunity, delayed hypersensitivity T cell

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primary response of antibody production

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occurs the first time a B cell is activated by an antigen; this B cell proliferates and produces plasma cells - plasma cells produce antibodies and memory B cells; response requires 3-14 days for there to be enough antibodies to be present to target the antigen; usually see disease symptoms in infected person

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secondary response to antibody production

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occurs at a later exposure to the same antigen; memory B cells start dividing rapidly and form plasma cells and also more memory B cells; faster and greater response to antigen - occurs in a few hours to a few days; memory T cells are responsible for secondary response

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cell-mediated immunity

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function of T cells; most effective response against intracellular micro-organisms; helper T cells can bind to a MHC I/antigen complex; this activates helper T cells

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how cell-mediated immunity activates helper T cells

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they activate cytotoxic T cells by increase in number and some differentiate to become memory T cells; cytotoxic T cells function in 2 ways by binding to target cells and release chemicals that cause cell to lyse or produce cytokines which promotes phagocytosis and inflammation

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binding of cytotoxic T cells to target cells and releasing chemicals that cause the cell to lyse

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virus infected cells, tumor cells, tissue transplants; major lysin is perforin

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perforin

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major lysin that helps helps cytotoxic T cells function; forms a hole in plasma membrane of target cell and allows water to enter cell

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delayed hypersensitivity T cells

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release cytokines in response to antigens - promotes phagocytosis and inflammation

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example of delayed hypersensitivity T cells

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poison ivy - antigen processed by Langerhan's cells in the skin and presented to delayed hypersensitivity T cells and they cause inflammatory response

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acquired immunity

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immunization, active natural immunity, active artificial immunity, passive natural immunity, passive artificial immunity

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immunization

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the deliberate exposure to an antigen or an antibody; active and passive immunity

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active immunity

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individual produces the immune response; lasts from weeks to lifetime; preferred method of vaccination

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passive immunity

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antibodies produced by a different individual and they are transferred to the non-immune individual; does noto last long; no memory cells produced

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active natural immunity

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natural exposure to an antigen produces an immune response; person usually develops disease symptoms and sometimes no symptoms develop, but they do develop immunity

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active artificial immunity

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vaccinations (flu shots); deliberate exposure to an antigen (the vaccine); live/killed microorganisms are sued, but they are still able to produce immune response; produces long lasting immunity and is the presferred method of developing immunity

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passive natural immunity

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transfer of antibodies from mother to her fetus or baby - some antibodies can cross placenta and protect fetus; nursing mothers provide antibodies in the milk to their infants; temporary immunity

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passive artificial immunity

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transfer of antibodies or cells from an immune individual to a non-immune individual; provides temporary immunity; useful for immediate protection; available for rabies, hepatitis, measles, tetanus, diphtheria, botulism, snake and black widow spider venoms; ex - antiserums - contain plasma and antibodies for passive artificial immunity

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aging of immune system

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primary and secondary responses decreases; more antigen required to produce a response, slower, less antibodies, fewer memory cells produced; ability of cell-mediated immunity to resist intracellular pathogens decrease like influenza; reactivation of pathogens, childhood chicken pox virus causes shingles