Fortress Body 1: Introduction to the Immune System PDF

09/11/23 Fortress body 1: introduction to the immune system and the threats to the body: part 2 Adaptive immune cells: CD4+ T cells ( Helper ): Develop in the thymus. Help B cells to produce antibodies and promote macrophage killing. Regulatory T cells suppress the activity of other immune cells. CD...

09/11/23 Fortress body 1: introduction to the immune system and the threats to the body: part 2 Adaptive immune cells: CD4+ T cells ( Helper ): Develop in the thymus. Help B cells to produce antibodies and promote macrophage killing. Regulatory T cells suppress the activity of other immune cells. CD8+ T cells ( killer ): Develop in the thymus. Kill cells infected with intracellular pathogens e.g viruses. B cells: Develop in bone marrow. Antibody production and neutralisation of pathogens, enhance pathogen uptake by phagocytes and activate complement. CD markers are used to de ne the type of lymphocyte and their function. Antibodies: Comprise of t wo heavy and t wo light chains with t wo identical antigen binding sites. The N-terminus of each heavy chain associates with one of the light chains to create t wo antigenbinding regions ( Fab region ). The C-termini of the t wo heavy chains combine to form the Fc region: Complement activation. Ican do these things Interaction with other immune cells via Fc receptor binding. IgG, IgE, IgD, IgA, IgM: different types and different functions. B cells: Antibodies are secreted versions of the B receptor, and have the same antigen speci city. Antibodies are found in serum and other bodily uids. Antibodies bind and neutralise pathogens, and enhance their uptake by phagocytes. Antibodies can activate complement to kill pathogens. T cells and Cell-mediated immunity: Recognition of pathogens: innate and adaptive: Innate: Individual cells of the innate immune system express a variety of PRR, which recognise molecular patterns shared across groups of pathogens. Adaptive: Each mature T or B cell bears a unique receptor that recognises one speci c antigen, rather than a general molecular pattern. Following infection, lymphocytes bearing receptors that recognise components of the invading pathogen proliferate, and differentiate into effector cells, generating a clone of cells bearing identical antigen receptors. B cells and T cells recognise antigens in fundamentally different ways: B cells recognise antigens circulating freely, or attached to the surface of microbes. These are often large molecules and B cells recognise only a small portion or epitope on the external surface of the molecule. T cells can directly recognise free antigen. T cell antigen receptors recognise peptides presented to them by MHC molecules. An accessory cell is required to process and present the antigen to T cells. Class it CD4t class I CD8t Dendritic cells process and present antigens to T cells in lymph nodes: MHC I Tcell for for What are MHCs: Cell surface molecules. Main function is to present antigens to T cells. Highly polymorphic, owing to selective pressures on immune system to recognise highly variable and constantly mutating pathogens. The most polymorphic genes in the human genome. Human MHC is also known as Human Leukocyte Antigen complex. Two types of MHC: Class I: Expressed on all nucleated cells. Recognised by cytotoxic T cells. Class II: Expressed on antigen presenting cells. Recognised by helper T cells. Role of the thymus: Immature T lymphocytes migrate from bone marrow to thymus where each clone generates a unique T cell antigen receptor. Many recognise self antigens and are deleted in the thymus to prevent autoimmune disease. Naive T cells, which escape deletion, have potentially used to receptors against foreign antigens. I summary