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5.Evaluate the purpose of the terms and describe the importance to clinical practice.Antigen: Harmful molecule that can react with antibodies or antigen receptors on B and T cellsoForeign, “non-self” oViruses, bacteria, fungi, parasitesoCan also be found on noninfectious environmental agents (pollens, food, bee venom, drugs, vaccines, transfusions)oTo function: at least a portion of a molecule’s chemical structure must be recognized by and bound to an antibody and/or to specific receptors on a lymphocyteSelf-antigen: AKA immunogens- can induce immune response resulting in production of antibodies or functional T cells oMost individuals tolerant of their own antigensoRegulated by T regulatory cells (T reg)Allergens: Antigens that induce an allergic responseAntibody: AKA immunoglobulin (Y shaped protein produced by plasma cells) used by immune system to neutralize pathogens (bacteria/viruses)oRecognize a unique molecule of harmful agent called antigenoNeutralize bacterial toxins > coat bacteria to enhance phagocytosis > formation of antibody complex > activates complement cascadeACTIVATION OF HUMORAL IMMUNITYB-cells stimulated by release of IL4 > B cells differentiate into plasma cells > produce antibodies > memory B cellsPlasma cells produce antibodies that will bind to the antigen > make antigen-antibody complexesMemory B-cells will act during secondary immune response > remember antigen > respond quicker in initiating the immunoglobulin creating processType of B-Lymphocyte CellFunctionImplications for Clinical Practice IgAFound in secretions/mucous membranes/ blood (IgA 1)-Prevents the attachment of microorganisms to the
mucous membranes-Secretions prevent dehydrationIgMProduced early in the primary immune response-Synthesized in neonatal life, may increase as response to infection in utero-High level indicate recentinfectionIgGMost prominent immunoglobulin-Binds with viruses, bacteria, toxins (most protective against infections)-Activates complement & binds to macrophages-Primary antibody in the 2ndary immune response-Levels rise in response to exposure to an antigen-Only immunoglobulin that crosses the placenta (major class of antibody found in newborns/fetus)IgELeast concentrated-Binds to mast cells, eosinophils, basophils-Involved in parasitic infections & hypersensitive reactionsMediator of many common parasitic infectionsIgDFound on surface of B lymphocytes, function not understood, limited informationACTIVATION OF T-CELLSAntigen presenting cells include B-lymphocytes, macrophages, and dendritic cells Antigen enters host → Macrophage engulfs antigen → antigen expressed on MHC class II → secretes IL 1 to attract CD4 cells → presents it to CD4-cells → CD4 differentiates into Th1 and Th2→ Th1 releases IL2 → activated cytoxic T- cells (Tc) → Tc receptor connects with MHC class I receptor on invader → cytoxic chemicals released → invader killed. Th2 releases IL4 → activates the humoral immune system