nester16 - Important Point: “An important hallmark of the...

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Unformatted text preview: Important Point: “An important hallmark of the adaptive immune response is that it has memory, a greatly enhanced response to re-exposure.” Key to understanding adaptive immunity is the interactions between antigens and immunesystem molecules, such as antibodies. Also important is the concept of tolerance, which is the ability of the immune system to ignore common body molecules. The primary lymphoid organs, are bone marrow and the thymus, where lymphocytes originate and/or mature (depending on type). Adaptive Immunity “In contrast to the innate immune response, which is always ready to respond to patterns that signify damage or invasion, the adaptive immune response matures throughout life, developing from the immune system arsenal the effective response against specific invaders as each is encountered.” Secondary Lymphoid Organs Primary Lymphoid Organs Adaptive Immunity Chapter 16: The Adaptive Immune Response The secondary lymphoid organs, such as Lymph Nodes, are the sites of interaction among immune system cells including with antigens presented by Antigen Presenting Cells. 1 Antibodies, Antigens, “Epitopes” Antigen stands for Antibody Generator. Antigens Antigens are molecules that are potentially recognized by adaptive immune-system molecules. “Recognition” specifically means a binding between the antigen and the immune-system molecule, such as between a immunogen and an antibody. Note, however, that an antigen within its “self” environment will not normally elicit (i.e., cause) an immune response. To describe antigens found in non-self environments, the term Immunogen is more correct, though we won’t bother making this distinction. Antigen-Antibody Interaction Epitope Epitope Epitope Etc. Epitope Epitope Epitope Different antibodies produced by different B cells are able to attach to distinct epitopes found on the same or different antigens. Antigen-Antibody Interaction Epitopes, T-Depend. Antigen An antigen consists of a number of recognizable regions known as Antigenic Determinants, a.k.a., Epitopes. This is an individual antigen found on the surface of a virus. There are a number of chemically and physically distinct regions on it to which different antibody types (blue) might bind. Antibody, a.k.a., Immunoglobulin “Red Flag” = host-toantibody binding region. Note the two identical antigen-binding sites; both are contained within identical variable regions. “Red Flag” = host-toantibody binding region. 2 Antigen Presentation by B Cell Immunoglobulin Actions Prevents binding to host tissues. Pilus as well as flagellum binding. These are now available for phagocytosis. Note binding by only one-half of the “Y”. Results in production of Abs agains TDependent Antigens (no Thelper binding, then no Ab). “Red Flag” host to antibody binding region. Recall that C3b can bind directly to cell. This is a host cell, covered with foreign antigens and therefore with antibody. Immunoglobulin Classes And remember, an Antibody is not an “Antibiotic!!!!!” Antigen-binding region. Clonal Selection Theory Antigen-binding region. If T Binding then Expansion Immunoglobulin in 3D Longest lived Ab & present in colostrum. Most abundant class (except in serum). Associated with allergies. Applies to both B and T cells. B cells are associated with Ab (Ig) production. T-helper binding occurs here. Takes place in 2° lyphoid organs. T cells are associated with cellmediated immunity. Memory B cells = longlasting immunity. 3 Including carbohydrate portion of LPS. Pri. & Sec. Immune Response Epitope Epitope 1° & 2 ° Immune Response (more detail) Clonal Expansion of Memory B cells—there are lots of ‘em! Both T cells and B cells are derived from hematopoietic stem cells found in bone marrow. T cells migrate to the thymus for further development (and hence the “T” in T cells, though the “B” in B cells stands for Bursa). T cells, during their development in the thymus, are subject to two round of selection. The first round is Positive Selection where only T cells that can bind MHC are retained. The second round is Negative Selection where T cells that recognize self antigens in association with MHC are deleted. The resulting T cells, both helper and cytotoxic, consequently can bind MHC (II or I, respectively), but only if complexed with non-self antigens. Antigen Recognition by T Cells Pos & Neg T Cell Selection Clonal Expansion of B cells. Epitopes, T-Independ. Antigen T-Independent Antigens Recognition by Cytotoxic T cell (CD8 receptor) Recognition by Helper T cell (CD4 receptor) 4 Cytotoxic Consequences CTL Immune Surveillance Stimulating T-Helper Cells Good summary of Adaptive Immunity! I.e., they tell their “friends” (other cytotoxic T cells). Apoptosis is cellular suicide which here is induced by the CTL. Adaptive Immunity Macrophages and Dendritic cells present antigens to, and thereby stimulate, T-helper cells. Link to Next Presentation 5 16 Adaptive Immunity Immunoglobulin Classes Longest lived Ab & present in colostrum. Most abundant class (except in serum). Associated with allergies. 16 Immunoglobulin Actions Recall that C3b can bind directly to cell. Prevents binding to host tissues. Pilus as well as flagellum binding. These are now available for phagocytosis. 16 This is a host cell, covered with foreign antigens and therefore with antibody. Clonal Selection Theory Applies to both B and T cells. B cells are associated with Ab (Ig) production. Takes place in 2° lyphoid organs. T cells are associated with cellmediated immunity. 16 Antigen Recognition by T Cells 16 Recognition by Cytotoxic T cell (CD8 receptor) Recognition by Helper T cell (CD4 receptor) ...
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This note was uploaded on 06/03/2011 for the course MCB 205 taught by Professor Abedon during the Spring '11 term at Ohio State.

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