SI2101 Immunology II PDF

SI2101 Immunology II Adaptive Immunity Dr. Louise Horrigan Physiology [email protected] University ofGalway.ie Learning To learn: Features of adaptive immunity Objecti...

SI2101 Immunology II Adaptive Immunity Dr. Louise Horrigan Physiology [email protected] University ofGalway.ie Learning To learn: Features of adaptive immunity Objectives of The 3 Rs of adaptive immunity Today’s Lecture Clonal selection Cell-mediated immunity 3 main types of T cell Antibody-mediated (humoral) immunity B cells Structure and functions of antibodies Primary and secondary antibody responses Features of Adaptive/Acquired Immunity Not born with it Develops (adapts) throughout a lifetime Slower to respond than innate system Recognises antigens with high specificity Has a memory function University ofGalway.ie  What cells are involved? Lymphocytes B lymphocytes Produce antibodies T lymphocytes Cell-mediated immunity T cells mature in the thymus. B cells mature in Colorized scanning electron micrograph of a T lymphocyte. Credit: the bone marrow. NIAID Image available from flickr.com Principles of adaptive immunity Recognise –Each cell has a specific receptor for a particular antigen –Recognition followed by clonal selection Respond –Cytokine secretion –Antibody production –Direct cell killing by T cells Remember –Memory cells Clonal selection Burnett, 1957 Each lymphocyte has receptors to bind a single antigen The lymphocyte repertoire is extremely diverse Very few cells of any one specificity Each is highly specific When a lymphocyte ‘finds’ its antigen, it binds and can become activated The activated cell divides rapidly to make lots of copies (clone) Effector cells Memory cells University ofGalway.ie Clonal Selection Occurs for both T and B cells Image from Wikimedia Commons, from Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/OpenStax This file is licensed under the Creative Commons Attribution 3.0 Unported license. Main Subtypes of T cells Regulatory T Helper T cells Cytotoxic T cells cells (Tregs) produce cytokines kills foreign cells suppress the to increase activity or infected host immune of B cells, cells response macrophages and other T cells Use the Produce the anti- perforin/granzyme inflammatory cytokine system interleukin (IL)-10 Normal T cell count is 600 – 1200 cells/μl AIDS: count < 200/μl B lymphocytes produce immunoglobulins (antibodies) B cell receptors (BCR) are antibodies Following B cell activation, they produce antibodies with same specificity as the BCR University ofGalway.ie Antibody (immunoglobulin) structure 4 polypeptide chains 2 identical heavy chains, 2 identical light chains Each chain has a variable (V) region and a constant (C) region Each antigen binding site (Fab) is composed of the V regions of the heavy and light chains Remaining heavy and light chain domains make up the Fc fragment  Five types of heavy chain giving rise to 5 isotypes  g, m, a, d, e IgG, IgE and IgD each have one Y unit IgA often has 2 Ig units (dimer) IgM has 5 Ig units (pentamer) IgG Comprises 70-75% of circulating immunoglobulins 4 subclasses: IgG1, IgG2, IgG3, IgG4 Only Ig to be transported across the placenta IgM Exists as a pentamer IgA Secretions Often exists as a dimer IgD Comprises