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Lecture

Principles of Adapative Immunity.pdf

5 Pages
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Department
Biology
Course Code
CAS BI 385
Professor
Trevor Siggers

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Description
Principles of Adaptive Immunity 3/25/14 12:10 PM Main difference from innate immunity- cell surface receptor • One type (B or T Cell receptors) • Specific for one pathogen. • Receptor selection is selected and expanded. Structure of surface of immunoglobulin, AB, and T- cell receptor • Ig- B cell receptor o Soluble form= antibody o Antigen binding site in light chain. § highly variable regions o Ig domain- small modular protein domain used in many immune system receptors. • TCR’s: Do not have a soluble form. o Antigen binding site has highly variable regions o Antibodies Specificity • Specific to their target pathogen. Gene rearrangement is a mechanism for generating diversity. • Gene segments- V, J, D • Rearrangements make functional proteins o Only happen in B and T cells Clonal selection- guiding principle of adaptive immunity • Clonal selection- lymphocyte selection • Clonal expansion- only a few lymphocytes will bind the pathogen. Initiating the adaptive immune response • Dendritic cells links innate and adaptive immune response o Moves to lymph node to initiate adaptive responseà adaptive effector cells move to infection site. • Rare T cells bind antigenà become effector T cellsà activate B cells • T Cells recognize degraded protein fragments o Linear peptides from pathogens. o Peptides are binded to MHC moleculesà TCR’s bind to peptide-MHC complex on dendritic cell surface. • Major histocompatibility complex (MHC) molecules o Loaded with antigen peptides and present them to TCRs o The ligand for TCR o Stretch peptides out in a linear fashion o Antigen Presenting cells carry peptide-MHC complex on their surface. o Two classes********* § Class 1 present antigens from intracellular pathways ú Peptides degraded in cytosol ú Occurs in all cells in the body*** ú CD8 binds MHC ú Present antigens to cytotoxic t cells that defend against intracellular pathogens. • Viral or bacterial intracellular-peptides § Class 2 present antigens from extracellular pathogens ú Peptides degraded in endocytic vesicles ú Only on APCs (dendritic cells, macrophages, and B cells).*** ú CD4 binds MHC • Present antigens to helper T cells o Enhance phagocytosis and train B cells. o Activate B cells to make antibodies. o Active cytokines and neutrophils. • Adaptive Immunity cont. 3/25/14 12:10 PM Antigen presenting Cells • Activating B Cells to produce Antibodies (Abs). o Plasma cellsàantibody factories • Abs are released into circulation or mucosal surfaces. o Primary function is to mark pathogens for destruction by phagocyte or other effector cell. • B cell receptors can bind any macromolecules and native antigens.*** o T cell receptors can only recognize degraded peptides in MHC complex. Helper T Cells help B cells to become Abs factories • Pathogens in Lymph node bind to native B cellsà undergoes receptor- mediated endocytosis. • Pathogen degraded peptides are presented via MHC class II. • Helper T cells that interac
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