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46 Cards in this Set
- Front
- Back
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What is the The Immune System? |
Represents a number of surveillance mechanisms: • that respond to infection by micro-organisms. • which can help repair damaged tissues. • that may help retard cancer development |
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How does the immune system do this? |
• The system is capable of recognizing self vs non-self • Can secrete protective substances into bodily fluids(humoral immunity) • Can launch a cellular response(cellular immunity) |
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What protects the body before the immune system is invoked? |
There are several mechanisms which protect thebody before the immune system is invoked. |
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What are these barriers? |
• Both physical and chemical in nature. • The skin, mucous membranes and cilia are examples ofphysical barriers. • Chemical barriers include mucous and the acidic propertiesof the stomach. • Surface epithelia can secrete specific microbicidalsubstances e.g. lysozyme and phospholipase in saliva andtears, and cryptidins and defensins in the gut. • Blood also contains antimicrobial substances e.g.complement |
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What are the two arms of the immune system? |
Innate Immunity Adaptive Immunity |
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What are the features of the innate immune system? |
Non specific. • Rapid. • Response to infections (non-self). • Response to altered self. • Can be humoral • or cell mediated. |
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What are the features of the adaptive immune system? |
Specific. • Slower to develop. • Response to infections (non-self). • Response to altered self. • Can be humoral • or cell mediated. • Has memory. |
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What are the features of the innate response? |
• Highly phagocytic • Contain lysosomal and microbiocidal proteins whichdestroy engulfed bacteria, cellular debris or foreignparticulate matter. • Neutrophils die after having disposed of their target • Macrophages can produce new lysosomes and continue toengulf and destroy foreign material. |
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What are macrophages? |
Macrophages can reside in a tissue orwander and survive for several weeks oreven months. In certain locations they havespecific names as well as specific functions: 1. Liver - kupffer cells 2. Bone - osteoclasts 3. Kidney – mesangial cells 4. Brain - microglia They are also found in lung, lymphoidorgans and connective tissue. |
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How long is neutrophil action? |
Neutrophils survivefor only a few dayson leaving thecirculatory systemand have to beconstantlyreplaced whichexplains their highconcentrationamong circulatingwhite blood cells |
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What are natural killer cells? |
Natural killer cells (lymphocyte lineage)attach to virally infected cells, transplantedcells, and some tumor cells by causingpores to form in the target cell membranewhich induces apoptotic death. |
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What do eosinophils contain? |
Eosinophils contain granules with cytotoxicproteins that attach to, and kill, parasites. |
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What are the features of adaptive immune cells? |
Cells are slower to react than innateimmune cells. • Respond to a near infinite range ofdifferent organisms. • Recognize foreign, possibly harmfulsubstances termed antigens. • Cells act to neutralize or destroy theseforeign substances. • Adaptive response can be both cellularand humoral in nature. |
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what are lymphocytes? |
• Make up about 30% ofWBC population. • Different functionalclasses of lymphocyte: B Cell T Cell • Circulate in the blood andlymph and becomeactivated in secondarylymphoid organs |
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What are the features of B cells? |
• Arise in bone marrow • Mature in the bonemarrow • Activated in 2' lymphoidorgans • Secrete antibodies specificto the target antigen • Long term immunitymaintained by “memory Bcells” |
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What are the features of the T Cells? |
• Arise in bone marrow • Mature in the thymus • Activated in 2' lymphoidorgans • Activated to induce a cell mediatedadaptive immuneresponse. • Long term immunitymaintained by “memory Tcells” |
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What do T cells do? |
• Direct and recruit other cells of the immunesystem • as well as attacking diseased cells directly. • Specific T cell receptors (TCR) are responsible forrecognition of antigen. |
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What are the four functional subsets? |
1.Helper T cells - can activate B cells and/or…2.Cytotoxic T cells - which can specifically killinfected cells. 3.Regulatory T cells - Help modulate responses.4.Memory T cells. |
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What are the features of the B cells? |
• Activated by antigen and helped along by helper Tcells • Secrete antibody when activated. • Antibodies can then either: 1. neutralize the pathogen 2. facilitate uptake by phagocytes (opsonization). |
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What are the 2 functional subsets? |
There are two functional subsets : 1. Plasma cells 2. Memory cells |
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What are antigens? |
• Substance that may or may not be harmful whichactivates the immune system. • It can be a protein, lipid, carbohydrate, or nucleicacid. • Can induce a T cell and/or a B cell response. |
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What are Antibodies? |
• Glycoprotein (immunoglobulins) that interactswith a specific antigen. • Can neutralize the antigen (if harmful) or they cancoat the antigen to induce phagocytosis(opsonization) by macrophages. • Staggering array of diversity. ~ 5x1013 or 5,000,000,000,000 varieties!! |
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What is the antibody structure? |
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What is the T cell receptor? |
Diversity generated by a similar somaticrecombination mechanism to antibodies. ~1018 or 1,000,000,000,000,000,000 varieties!! |
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What happens in lymphocyte activation? |
Lymphocyte activation occurs when lymphocytes(B cells or T cells) are triggered through antigen-specific receptors on their cell surface. This causes the cells to proliferate and differentiate into specialized effector lymphocytes |
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What is the Link Between Innate andAdaptive Immunity? |
The Antigen Presenting Cell (APC): • Vital for activation of lymphocytes. • Include macrophages, dendritic cells, and Blymphocytes. • The antigen is taken up by phagocytosis by anAPC (e.g. macrophage or a professional APC). • These cells then migrate to lymphoid tissue topresent antigen to the lymphocytes. • The antigen is presented on the surface of theAPC and shown to a T cell. • If the T cell has the correct receptor to bind to theantigen the immune response will proceed. |
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What are The Professional APCs:Dendritic Cells? |
Sentinels of the Immune System • Derived from bone marrow blood cell precursors. • Reside in many tissues but can also circulate.• Resident DCs often given special namesdependent on their localization (e.g. langerhanscells of the skin). • Often in close contact with the externalenvironment where they search for antigen. • Capable of migrating to lymph nodes where theyhave a chance to present their antigen to T cells. |
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What are the features of The Immune System as aDefence Organization? |
1) Its function is selective destruction. 2) It is large, complicated and elaborate. 3) It is expensive. 4) It is wasteful. 5) It has distinct components performing apparentlyidentical functions. 6) It is slow to react. 7) It is prepared for events that never happen.8) It fights today’s threats with the solutions of pastproblems. 9) It is susceptible to corruption. 10) It can destroy that which it protects. |
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What are the The Tissues of theImmune System? |
• Primary Lymphoid Tissues - where immaturelymphocytes acquire the capacity for antigenrecognition. Bone marrow- T cell development, and B cell development andmaturation Thymus- T cell maturation • Secondary Lymphoid Tissues- Sites of lymphocyteactivation Lymph nodes- Screens lymph Spleen- Screens blood borne antigens Mucosa Associated Lymphoid Tissue (MALT)- Screens mucosa |
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What is the thymus? |
A bilobed encapsulated organ located in the lowerneck. |
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What is the thymus the site of? |
• Site of T cell maturation 1) acquisition of T cell immunocompetence 2) development of immunological self tolerance |
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What happens to immunocompetent T cells once they have entered the circulation? |
Once immunocompetent T cells have beenselected they enter the circulation and migrate toother lymphoid organs. |
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What does the thymus look like? |
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Where are the progenitor cells frombone marrow? |
cortex |
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Where does proliferation &selection take place ---> Mature T cellsenter circulation? |
medulla |
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What happens at the secondary lymphoid tissues? |
Secondary Lymphoid Tissues- Sites where immuneresponses are carried out. |
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What do the different tissues do? |
Lymph nodes- Screens lymph Spleen- Screens blood borne antigens Mucosa Associated Lymphoid Tissue (MALT)- Screens mucosa |
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What are the lymph nodes? |
Small organs found in groups or chains insites where lymphatic vessels drain ananatomic region. |
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What are their two main functions? |
1. Phagocytic cells within the nodes act asnon specific filters of particulate matter e.g.carbon & micro-organisms, preventing themfrom reaching the general circulation. 2. Location where lymphocytes can interactwith new antigens and APCs, whichfacilitates activation of an immuneresponse. |
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What is the structure of lymph nodes? |
Structure- • Surrounded by a fibrocollagenous capsule fromwhich trabeculae extend into the node forming asupportive network. • The surface is penetrated by a number of afferentvessels which drain into the node leading to thehilum where the efferent vessels transport thelymph into the collecting vessels.• The parenchyma consists of an extracellularmatrix supporting regions of lymphocyteaggregates (follicles) where immune activationtakes place. |
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What are the follicles? |
Follicles- regions of Bcell activation • The germinal centerconsists of activated,dividing B cells, witha few T cells. • The mantle zone isprimarily resting Bcells. • T cells make up themajority of cells inthe paracortex. |
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What is the spleen? |
• Responsible forimmunological responsesagainst blood antigens. • Removes aged or defectiveblood cells. • Haematopoietic organ inthe embryo. |
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What are the red pulp and white pulp? |
Red Pulp Responsibleforfiltering blood White Pulp Immunologicalregion of the organ |
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What are splenic follicles similar in structure to? |
Splenic folliclessimilar in structure- and function - tofollicles of lymphnodes |
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What is the Mucosa Associated Lymphoid Tissue(MALT)? |
• Populations of immune cells in the mucosaof many epithelial tissues. • They may be organized aggregations ofimmune cells or simply be a collection ofscattered lymphocytes within the tissue. • Functionally analogous to lymph nodes. |
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What is a peyer's patch? |
Peyer’s Patch(Gut Associated Lymphoid Tissue) |
