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Adaptive immunity - 2023.pptx
- 1. Adaptive (Acquired) Immunity Dr.Sherzad M Taher Medical Immunology College Of Pharmacy UoD September 19, 2023 -
- 3. Types of Acquired Immunity 1. Naturally acquired immunity. It is the immunity which could be acquired passively during live to human from:-mother or actively through infections. 2. Artificially acquired immunity . It is the immunity which could be acquired passively to human through: immunoglobulin injection or actively through vaccination.
- 4. Aquired (specific) immunity Two mechanisms: 1) Humoral immune response: - Antibodies are produced by B-lymphocytes - These have the ability to recognize and bind specifically to antigen that induced their formation 2) The cell mediated immune response (CMI) - It is mediated by certain types of T-lymphocytes - T-lymphocytes recognize foreign material by means of surface receptors - T-lymphocytes attack and destroy foreign material directly or through release of soluble mediators i.e. cytokines
- 5. Adaptive Immunity Adaptive immunity displays four characteristic attributes: Antigenic specificity Diversity Immunologic memory Self/nonself recognition Anamnestic response
- 6. Antigenic specificity The antigenic specificity of the immune system permits it to distinguish subtle differences among antigens. Antibodies can distinguish between two protein molecules that differ in only a single amino acid.
- 7. Diversity The immune system is capable of generating tremendous diversity in its recognition molecules, allowing it to recognize billions of unique structures on foreign antigens
- 8. Immunologic memory Once the immune system has recognized and responded to an antigen, it exhibits immunologic memory; that is, a second encounter with the same antigen induces a heightened state of immune reactivity. Because of this attribute, the immune system can confer life-long immunity to many infectious agents after an initial encounter.
- 9. Self/non-self recognition The ability of the immune system to distinguish self from nonself respond only to non-self molecules is essential, for, as described below, the outcome of an inappropriate response to self molecules can be fatal.
- 10. Anamnestic response Rapid production of an antibody on the second (or subsequent) encounter with the same antigen.
- 12. B Lymphocyte B cell development and maturation B cell activation and differentiation
- 13. B Lymphocyte B cell development and maturation B lymphocytes mature within the bone marrow; when they leave it, each expresses a unique antigen-binding receptor on its membrane . This antigen-binding or B-cell receptor is a membrane-bound antibody molecule. Antibodies are glycoproteins that consist of two identical heavy polypeptide chains and two identical light polypeptide chains. Each heavy chain is joined with a light chain by disulfide bonds, and additional disulfide bonds hold the two pairs together. The amino-terminal ends of the pairs of heavy and light chains form a cleft within which antigen binds.
- 14. B Lymphocyte
- 15. B Lymphocyte B cell activation and differentiation When a naive B cell (one that has not previously encountered antigen) first encounters the antigen that matches its membrane bound antibody, the binding of the antigen to the antibody causes the cell to divide rapidly; its progeny differentiate into : memory B cells effector B cells ( plasma cells.) Memory B cells have a longer life span than naive cells, and they express the same membrane-bound antibody as their parent B cell. Plasma cells produce the antibody in a form that can be secreted and have little or no membrane-bound antibody. Although plasma cells live for only a few days, they secrete enormous amounts of antibody during this time. It has been estimated that a single plasma cell can secrete more than 2000 molecules of antibody per second. Secreted antibodies are the major effector molecules of humoral immunity.
- 16. B Lymphocyte
- 17. Different types of B cells have different receptor molecules. When a pathogen (germ) locks on to a receptor, that type of B cell is selected. The selected B cell divides rapidly to make lots of copies of itself. The copies make lots of antibodies against the pathogen. Selection of B cells by antigen (clonal selection) (The key of specificity of adaptive immunity)
- 18. Bellow is a diagram of Clonal selection in B cells
- 19. T Lymphocyte T cell development and maturation T cell activation and differentiation
- 20. T Lymphocyte T cell development and maturation T lymphocytes also arise in the bone marrow. Unlike B cells, which mature within the bone marrow, T cells migrate to the thymus gland to mature. During its maturation within the thymus, the T cell comes to express a unique antigen-binding molecule, called the T-cell receptor, on its membrane. Unlike membrane-bound antibodies on B cells, which can recognize antigen alone, T-cell receptors can recognize only antigen that is bound to cell-membrane proteins called major histocompatibility complex (MHC) molecules.
- 21. T Lymphocyte T cell activation and differentiation When a naive T cell encounters antigen combined with a MHC molecule on a cell, the T cell proliferates and differentiates into memory T cells and various effector T cells. There are two well-defined subpopulations of T cells: T helper (TH) : start the immune response helper T cells continue to differentiate into individual subsets of helper T cells. T cytotoxic (TC) cells : kill the bodys abnormal cells, like virus-infected cells and cancer cells T suppressor (TS) cell : suppress the activities of other T cells, helping to end the immune response T helper and T cytotoxic cells can be distinguished from one another by the presence of either CD4 or CD8 membrane glycoproteins on their surfaces . T cells displaying CD4 generally function as TH cells, whereas those displaying CD8 generally function as TC cells
- 22. T Lymphocyte T cell activation and differentiation Many different subsets of helper T cells perform various functions : Th1 - which mediates cyotoxic T cell activity through cytokine release, Th2 - which presents antigens to B cells. Th17 - which only differentiates from effector cells if certain cytokines are present, is important in regulating and inhibiting T-reg cell activity. T-memory cells: The population of these cells increases only after their initial exposure to an antigen. If the same antigen presents itself again, they are triggered to convert themselves into cytotoxic T cells and kill the pathogen.
- 23. T follicular helper cells (Tfh) are a specialized subset of CD4+ T cells that were first identified in the human tonsil. They play a critical role in protective immunity helping B cells produce antibody against foreign pathogens. Tfh are located in secondary lymphoid organs (SLOs), including the tonsil, spleen and lymph nodes.
- 24. T cell training Positive selection of the T-cell Negative selection
- 25. T cell training Positive selection of the T-cell Is a process in the thymus that selects immature T cells with receptors that recognize peptide antigens presented by self-MHC molecules. Only cells that are positively selected are allowed to continue their maturation Then go to the spleen and lymph nodes, and wait for antigens. If they recognize an antigen, some will go into battle and others become memory cells .
- 26. Step 1. Positive selection occurs in the thymic cortex MHC self- recognition molecules
- 27. T cell training Negative selection Process in the thymus whereby developing T cells that recognize self antigens are induced to die by apoptosis.
- 28. Step 2. Negative selection occurs in the thymic medulla.