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81 Cards in this Set
- Front
- Back
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what is the first line of defense composed of?
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external physical barriers to pathogens (ie: skin, mucous membranes)
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what is the second line of defense composed of?
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protective cells, blood-borne chemicals, processes that inactivates/ kills invaders
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what is innate immunity?
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immunity that are present at birth prior to contact with infectious agents/their products
- first line of defense - second line of defense |
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what is adaptive immunity?
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third line of defense that responds against a unique species or strain of pathogens that invades the body.
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what are formed elements and what are the 3 types of formed elements?
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cells and cell fragments suspended in the plasma
3 types: - erythrocytes - platelets - leukocytes |
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characteristics of erythrocytes
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- most numerous formed elements in the body
- carry O2 and CO2 in the blood |
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characteristics of platelets
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- pieces of large cells (megakaryocytes) that have split into small portions of cytoplasmic membranes
- involved in blood clotting |
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characteristics of leukocytes
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- formed elements that are involved in defending body against invaders
- aka: White Blood Cells (WBC) |
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2 groups of leukocytes (based on their appearance under microscope)
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1. granulocytes (have large granules in the cytoplasm that stain different colors)
2. agranulocytes (does not have large granules in cytoplasm) |
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types of granulocytes
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1. basophils: stains blue (with basic methylene blue)
2. eosinophils: stains red to orange (with acidic dye eosin) 3. neutrophils: stains lilac (with acidic/basic dyes mix) |
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diapedesis or emigration
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a process of squeezing between (leaping out of blood) the cells lining capillaries (smallest blood vessels) to attack invading microbes (when neutrophils and eosinophils phagocytize pathogens that invade tissues)
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3 types of blood stem cells made in bone marrow and the cells produced by them
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1. Erythroid stem cell, makes:
-- erythrocytes (for gas transportation) 2.Myeloid stem cells, makes: -- platelets (for blood clotting and inflammation) -- basophils (for inflammation) -- neutrophils ( for innate immunity, 2nd line of defense, phagocytosis) -- eosinophils (for innate immunity, 2nd line of defense, phagocytosis) -- monocytes (for innate immunity, 2nd line of defense, phagocytosis) 3. Lymphoid stem cells, make: -- lymphocytes (adaptive immunity) |
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what are leukocytes made up of:
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- basophils
- neutrophils - eosinophils - monocytes - lymphocytes |
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2 types of agranulocytes
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1.lymphocytes
-- smallest leukocytes -- the nuclei almost fill a whole cell 2. monocytes --leave the blood and mature as macrophages (phagocytic cells of the 2nd line of defense) -- functions: phagocytic and recycle dead body cells |
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what are the fixed macrophages and what are they consist of?
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Phagocytes within a specific region.
They consist of: 1. Alveolar macrophages (in the lungs) 2. Microglia (in CNS) 3. Kupffer cells (in liver) |
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what are wandering macrophages?
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macrophages that leave the blood via diapedesis and perform their phagocytotic function while travelling throughout the body
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why is the mononuclear phagocytic system considered a functional system rather than anatomical (structural) system?
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Because it is composed of cells located in many body systems, that share a common function: phagocytizing invaders
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chemotaxis
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movement of a cell either toward a chemical stimulus (positive chemotaxis) or away from chemical stimulus (negative chemotaxis)
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5 steps of continuous process of phagocytosis
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1. chemotaxis
2. adherence 3. ingestion 4. killing 5. elimination |
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chemotactic factors
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1. peptides derived from complement
2. chemokines (chemicals released by leukocytes at a site of infection) |
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adherence
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process of phagocytes attachment to microorganism via the binding of complementary chemicals (glycoproteins found in the membranes of the cell), when arriving at a site of infection
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opsonization
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a coating process using a specific anti-microbial protein/ complement proteins/ antibodies (opsonin), that's performed by phagocytic cells
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phagosome
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food vesicle thats formed by the fusing process when encompassed microbe is internalized
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natural killer lymphocytes (cells)
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type of nonspecific defense leukocytes that works by secreting toxins onto surfaces of virally infected cells and neoplasma (tumors)
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complement (system)
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set of serum proteins designated numerically according to the order of their discovery
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mononuclear phagocytic system
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system consisting of macrophages of all types:
--fixed macrophages --wandering macrophages --monocytes that are attached to cells that line heart chambers, blood vessels, and lymphatic vessels |
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eosinophilia
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abnormally high number of eosinphils in the blood, often a sign of helminth infestation
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ways neutrophils destroy microbial cells without phagocytosis:
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1. enzymes in neutrophils cytoplasmic membrane add electrons to O2, creating highly reactive superoxide radical O2 and hydrogen peroxide
2. another enzyme converts these into hypochlorite (active microbial ingredient in household bleach). 3. another enzyme in the membrane makes nitric oxide (powerful inflammation inducer) |
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Neutrophil Extracellular Traps
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extracellular fibers composed of DNA, histones, and protein generated by neutrophils to bind and kill both Gram-neg and Gram-pos bacterias in their vicinity
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Complement System
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-- set of serum proteins designated numerically according to the order of their discovery
-- initially act as opsonin and chemotactic factors and indirectly trigger inflammation and fever -- end result of full complement system is lysis of foreign cell |
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2 ways to activate Complement System
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1. Classical Pathway: binding of antibodies to antigens activate complement
2. Alternate Pathway: binding of Factors B, D, and properdin to endotoxin or glycoproteins in cell walls of bacteria/fungi activates complement. |
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Complement Cascade
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Combination of series of pathways (classic and alternate) in amplifying chemical reactions, leading to opsonization inflammation and complete membrane attack complex and cell lysis
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Membrane Attack Complexes (MAC)
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end products of the entire cascade of activation of complement
-- Gram-neg bacteria extremely sensitive to MAC because of their exposed outer membrane -- Gram-pos has thick layer of peptidoglycan, they are more resistant to MAC |
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Interferons
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= protein molecules released by host cells to NONSPECIFICALLY inhibit spread of viral infections
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3 basic classes of interferons
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1. alpha interferon
2. beta interferon 3. gamma interferon |
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ALPHA and BETA interferons
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ALPHA INTERFERON
-- secreted by virally infected monocytes, macrophages and some lymphocytes within hours of infection BETA INTERFERON --secreted by fibroblasts (undifferentiated cells in connective tissues like cartilage, tendon and bone) when infected by virus * interferons do not protect the cells that secrete them (these cells already infected with virus) * interferons activate Natural Killer lymphocytes and trigger protective steps in neighboring uninfected cells |
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Anti Viral Protein (AVP)
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protein that is produced by the binding of interferon receptors on the cytoplasmic membrane of neighboring cells with alpha and beta interferons
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GAMA interferon
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= produced by activated T- and lymphocytes and NK lymphocytes
-- appear later than alpha and beta interferons -- its action in stimulating the activity of macrophages give its name "Macrophage Activation Factor" |
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B-Cells
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-- originated from stem cells in bone marrow and liver then travel directly to lymphoid tissues
-- have antigen receptors on cell surfaces -- when B-cell is exposed to a specific antigen, i will divide and differentiate into clone of PLASMA cells -- plasma cells then make antibodies directed against specific antigen that activate the original Bcell -- the antibodies are found in extracellular fluids plasma, lymph and mucus. -- part of HUMORAL immune system (primarily against agents circulating freely in the bodily fluids (bacteria, bacterial toxins and circulating viruses) |
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T-Cells
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-- originated as stem cells in liver and bone marrow
-- mature in the Thymus gland (2 to 3 days) -- after maturing, Tcells migrate to lymphoid tissues (lymph nodes and spleen) -- part of CELL-MEDIATED immune system -- cell mediated immune system most effective against bacteria and viruses located WITHIN the host cells. -- cell mediated immunity also responsible for rejection of foreign tissues when transplanted and identify cell bodies as being "self" (important in recognizing cancer) |
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Antigen
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= Foreign substance that does not belong in the body
* usually made of proteins/ large polysaccharides. Lipids and nucleic acids are antigenic only when combined with polysaccharides/protein * components of invading microbes (capsule, cell walls, flagella, fimbrae, toxins, coats of viruses) * each antigen has numbers of antigenic determinants |
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epitope
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aka: antigenic determinant
* will bind with antibody molecules at binding sites * antibody bind to identical determinants on the same/ different cell at the same time causing AGGLUTINATION |
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Hapten
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= a small molecule that can elicit an immune response only when attached to a large carrier such as a protein; the carrier may be one that also does not elicit an immune response by itself. (In general, only large molecules, infectious agents, or insoluble foreign matter can elicit an immune response in the body.)
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Results of antibodies binding to antigens:
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1. Agglutination
2. Opsonization 3. Neutralization 4. Complement Activation * Basically tagging the foreign molecules for destruction by phagocytes. * Antibody does not damage the antigen directly itself |
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Agglutination
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= The process by which suspended bacteria, cells, or other particles are caused to adhere and form into clumps to enhances phagocytosis and reduced number of infectious units
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Opsonization
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= the process by which a pathogen is marked for ingestion and destruction by a phagocyte.
Opsonization involves the binding of an opsonin (i.e., antibody) to a receptor on the pathogen's cell membrane. After opsonin binds to the membrane, phagocytes are attracted to the pathogen. |
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Neutralization
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by binding to a toxin, antibody molecule may block active site of the toxin.
-- antibodies neutralize toxins -- antibodies bind to viruses and bacterias and block their ability to attach to cells |
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Complement Activation
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-- binding of antibody to an antigen result in the activation of complement resulting all mediated reactions including cell lyses.
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Inflammation
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--one of the action of complement is to attract phagocytes to area and increase blood vessels permeability
-- by binding to antigen, antibodies indirectly help promote process of inflammation |
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Antibody-Dependent Cell Mediated Cytotoxicity (ADCC)
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-- target organism is also coated with antibodies, but destruction of the pathogen is by nonspecific immune cell
-- important in resistance against parasitic worms (too large for macrophages to phagocytize) -- ADCC is a mechanism of cell-mediated immunity whereby an effector cell of the immune system actively lyses a target cell that has been bound by specific antibodies. -- It is a part of the humoral immune response and adaptive immune system, can act to limit and contain infection. -- Classical ADCC is mediated by nonspecific immune cells natural killer (NK) cells, macrophages, neutrophils and eosinophils. -- Nonspecific immune cells have receptors for the Fc region of the antibody molecule. |
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Apoptosis
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Cell suicide
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Memory cells
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-- 2 types: memory B-cells and memory T-cells
-- Memory B-cells: antibody producing cell -- Memory T-cells: infection fighting cells -- Responsible for the rapid response to a second infection --The Memory Cells are the second cell type produced by the division of B cells. These cells have a prolonged life span and can thereby "remember" specific intruders. -- T cells can also produce memory cells with an even longer life span than B memory cells. -- The second time an intruder tries to invade the body, B and T memory cells help the immune system to activate much faster. The invaders are wiped out before the infected human feels any symptoms. The body has achieved immunity against the invader. |
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Functions of Complement System
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-- Opsonization: enhancing phagocytosis of antigens
-- Chemotaxis: attracting macrophages and neutrophils -- Lysis: rupturing membranes of foreign cells -- Clumping of antigen-bearing agents -- Altering the molecular structure of viruses |
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5 Types of Immunoglobulin (Ig's)
(defined by amino acid sequence) |
1. IgG (the standard Y)
2. IgM (a pentamer five Y's held together by a J-chain) 3. IgA (a dimer) 4. IgE ( monomer) 5. BCR (B Cell receptor) |
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IgA (immunoglobulin A)
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* most abundant type in blood serum and tissues
* enhances phagocytosis when bound to antigens * neutralizes toxins and viruses * protects against bacteria by triggering complement system * it crosses placenta and protects fetus |
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IgM (Immunoglobulin M)
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* stays in the blood
* involved in agglutination reactions * first antibody produced in response to an infection (second infection usually produce IgG) * enhances phagocytosis * first antibody produced on initial exposure to an antigen * few days into infection, IgG will be produced * if a second exposure takes place, IgM levels will rise, but less abundant than IgG |
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IgA (Immunoglobulin A)
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* most commonly in mucus and secretions (saliva, tears, breast milk)
* the secretory form is a dimer, serum IgA is a monomer * prevent attachment of pathogens in mucosal surfaces (important in resistance to respiratory infections) * ie: presence in colostrum helps protect infant from gastrointestinal infections |
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IgE (Immunoglobulin E)
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* attach to mast cells and basophils to histamine release causing inflammation
* involved in allergic reactions (elevated during parasitic infections and allergic reactions) * attract phagocytic cells * when an antigen (pollen) attach to IgE on a mast cell/ basophil, the cell release histamine (a protective response especially towards parasitic worms) |
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BCR (B Cell Receptor)
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* found on surface of B cells
* each BCR is specific to 1 antigenic determinant * when antigen binds to a BCR, clonal selection occurs |
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Types of Immunity:
1. naturally acquired * active * passive 2. artificially acquired * active * passive |
1. Naturally Acquired Active Immunity:
-- antigens enter body, body produces antibodies and specialized lymphocytes -- can be lifelong for some disease (chicken pox and measles) 2. Naturally Acquired Passive Immunity -- when antibodies pass from mom to fetus via placenta -- IgG crosses placenta and will confer passive immunity to infant (only lasts weeks/ months) 3. Artificially Acquired Active Immunity (ie: vaccination) -- in response to vaccination, body produces antibodies and specialized lymphocytes 4. Artificially acquired Passive Immunity -- when antibodies (not antigens) are administered. -- antibodies are from a person already immune to the disease -- ie: Gamma Globulin as travel shot or tetanus immune globulin -- short lived because antibodies are degraded by recipient (usually 3 wks) |
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Cell Mediated Immunity
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-- mediated by Tcells
-- Tcells react specifically with only 1 antigen -- Tcells undergo clonal selection (divide and differentiate on exposure to specific antigen) -- Tcells also have TCR (T Cell Receptor) that bind certain antigen -- Tcells generate memory Tcells -- directed to endogenous antigens (associated with cells like viral antigens or novel antigens on urface of cancer cell) |
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Types of T-Cells (based on characteristic cell surface molecules)
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1. Cytotoxic T-Cell (Tc)
2. Helper T-Cell (Th) 3. Antigen Presenting Cells (APC) |
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Cytotoxic T-Cell (Tc)
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-- destroy target cells on contact
-- effective against viruses and bacteria inside host cells (can't be reached by antibodies) -- will secrete PERFORIN molecules once its bound to a cell (perforin forms a pore in the membrane of larger cell causing it to lyse) -- has to bind 2 molecules (MHC molecule and foreign antigen on surface of infected cell), a self and a non-self, side by side before it destroys it |
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Major Histocompatibility Complex (MHC)
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--self molecules (specific/ unique to that person) involve in auto-immunity
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Helper T-Cell (Th)
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-- produce cytokines
--Type 1 Th (Th1) produce cytokines that activate and stimulate proliferation of Tc -- Type 2 Th (Th2) make cytokines that interact with Bcells and are important to production of antibodies (by Bcells and antibodies against T-dependent antigens) -- stimulated to produce cytokines when bound to MHC-antigen complex (a special kind of macrophage called Antigen Presenting Cell) |
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Antigen Presenting Cells (APC)
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-- macrophages or dendritic cells
-- ingest and process antigens and display their fragments on the cell surface -- T-cell will recognize antigenic fragment on APC only when it's associated with a MHC molecules -- secretes Interleukin-1 -- certain APC stimulate cell mediated response (specific) by generating cytokines which stimulate Tc cells to proliferate and attack infected cells |
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Interleukin-1 and Interleukin-2
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Interleukin-1:
* a kind of cytokine that stimulates Th cell to secrete Interleukin-2 Interleukin-2: * stimulated that Tcells to form a clone of type 2 Th cells * type 2 Th cells will activate B-cells which proliferate and mature into cells producing antibody specific to the offending antigen |
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T-independent Antigen
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--antigens that can stimulate B-cells directly without help of T-cells
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T-Dependent Antigen
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--antigens (mainly proteins found on viruses/bacteria/ foreign RBC/ hapten with carrier molecules) that need assistance of Th cells to ensure the production of antibodies
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CD4 and CD8 (classification of T cells based on plasma membranes/ cell surface molecules)
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CD4 cells:
--primarily Th cells (helper Tcells) CD8 cells: -- cytotoxic T cells (Tc) |
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Diagnostic Tests that use Antibodies
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1. Flourescence Activated Cell Sorting (FACS)
2. |
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FACS-- Flourescence Activated Cell Sorting
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* used to count CD4 and CD8 cells in AIDS patients (amount of CD4 cells in AIDS patients are decreased)
* mixture of cells are mixed with antibodies (has fluorescence marker), antibody binds to the cells, cells are squeezed one at a time via cell counter |
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ELISA -- Enzyme Linked Immuno Sorbent Assay
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* used to detect antigens in serum (hormones or pathogens)
* ie: home pregnancy kit that detects presence of Human Chorionic Gonadotropen (HCG) hormone, only present in pregnant women * measure antibodies that appear in blood serum as infection progress (in AIDS patient) |
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NonSpecific Defense
vs Specific Defense |
Non Specific Defense:
--defenses that protect against any pathogen, regardless of species Specific Defense --protect against particular pathogen. --require specialized cells of immune system (lymphocytes) and production of antibodies |
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First line of defense
Second line of defense Third line of defense |
First line:
--skin, mucous membrane Second line: --phagocytic WBC Third line: --Specialized lymphocytes, --Bcells and Tcells |
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why is skin a barrier to infection?
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-- it's relatively dry
-- it's exposed to radiation (sun), which is a mechanical barrier -- it has secretion which inhibits growth perspiration (high in salt, contains lysozyme breaking down Gram-neg bacteria) --it has sebum (from oil glads) which is chemical barrier |
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Respiratory system as mechanical barrier to infections:
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-- hairs that filter out dust and microbes
-- has mucous -- has cilliary escalator (ciliated cells propel microbes up toward the mouth) -- epiglottis keeps microbes from getting into lower respiration system |
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Second Line of Defense
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-- involves phagocytic WBC
-- inflammation and certain antimicrobial substances are in the 2nd line of defense (nonspecific) |
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Neutrophils
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-- stain pale purple with mix of acid and base stains
-- lobed nuclei -- considered Poly Morpho Nuclear (PMN) leukocytes -- motile and phagocytic |
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Inflammation and its symptoms
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Inflammation:
localized phenomenon Symptoms: -- redness -- pain -- heat -- swelling |
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Roles of Inflammation
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--destroy the agent of injury
--isolate the area of injury, confining the agent -- repair muscle or damaged tissue |
