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Lecture 16 Cellular Cooperation and Antigen Recognition

Lecture 16 Cellular Cooperation and Antigen Recognition. Cellular Cooperation. antigen. T. B. H. Plasma Cells. Antigen presentation to T and B cells by APC T cells elaborate cytokines to facilitate B cell proliferation and maturation. Antibody secretion by plasma cells.

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Lecture 16 Cellular Cooperation and Antigen Recognition

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  1. Lecture 16Cellular Cooperation and Antigen Recognition

  2. Cellular Cooperation antigen T B H Plasma Cells Antigen presentation to T and B cells by APC T cells elaborate cytokines to facilitate B cell proliferation and maturation Antibody secretion by plasma cells Antigen presenting cell

  3. Antigen Presenting Cells • Must be capable of processing antigen from extracellular and intracellular pathogens • Must present processed antigen on MHC class I & II molecules • Must express co-stimulatory molecules (cytokines)

  4. Types of Professional Antigen Presenting Cells • Macrophages/monocytes • Dendritic cells (e.g.., Langerhan’s cells) • B cells

  5. Properties of Professional Antigen-Presenting Cells

  6. Cellular Cooperation and Antigen Recognition + Class II MHC- associated antigen APC Extracellular Antigen CD4+ Helper T Lymphocyte

  7. The Role of Adjuvants • Depot effect • antigen persists for long period • resistance to rapid degradation • Macrophage activation • production of non-specific enhancing factors • Non-specific T cell signal • provides "second" signal to B cell normally provided by T cell

  8. Types of Adjuvants • Freund's Complete Adjuvant (Water-in-oil emulsion) • mineral oil • emulsifying agent • microbial preparation (eg. heat-killed extract of Mycobacterium tuberculosis) • aqueous phase containing antigen • Aluminum Hydroxide Gel • Microbial Adjuvants • C. parvum • BCG • Peptides and Synthetic Polymers

  9. Effector Mechanisms • Mechanisms that are used by the immune system to eliminate pathogens (or other substances) from the body • Cellular effector mechanisms • Activated T cells • Natural killer cells • Humoral effector mechanisms (antibody) • Neutralization • Opsonization • Complement activation • Antibody-dependent cell-mediated cytotoxicity (ADCC)

  10. Effector Activity Against Pathogens

  11. Cytokines • Polypeptides produced by a variety of cell types including T lymphocytes. • Cytokine production is triggered by specific receptor binding and subsequent signal transduction pathways • Cytokine repertoire is dependent on cell type triggered, receptors present on that cell type. • Cytokines act on cells that possess receptors for them.

  12. Lymphocyte Migration, Activation, and Effector Function Depends on Cell-Adhesion Molecules • A variety of cell surface polypeptides serve as receptors to ensure appropriate cell-cell interactions. These polypeptide include: • Selectins • Integrins • Immunoglobulin Superfamily • Mucin-like Vascular Addressins

  13. T-cell Mediated Cytotoxicity • Necrosis • Programmed cell death or apoptosis

  14. Summary • Effector cells and antibodies play critical roles in almost all adaptive immune responses • Antigen-presenting cells play critical role in processing and presenting antigen to T cells • Cytokines are released by a variety of cell types and regulate a variety of biological effects • T-cell mediated cell death is largely via apoptosis

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