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MIMM 314 (2)
Chapter 1


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McGill University
Microbiology and Immun (Sci)
MIMM 314

Cristina Mitric ----- Janeways Immunobiology ----- Chapter 1 Principles of Innate and Adaptive Immunity Functions of the immune response a. Immunological recognition =detect presence of an infection Role: WBC (innate), lymphocytes (adaptive) b. Immune effector functions, such as the complement system of blood proteins, antibodies, and the destructive capacity of WBC and lymphocytes c. Immune regulation = the ability of the immune system to self-regulate Failure results in allergies or autoimmune diseases. d. Immunological memory = protect against recurring disease due to the same pathogen The first cells that respond are phagocytic WBCs, such as macrophages, that form part of the innate system. (by toxic chemicals and degradative enzymes also) -highly specialized antigen receptors on the lymphocyte surface. Pathogens Viruses Bacteria Fungi Parasites WBC= leukocytes Both innate and adaptive immune responses depend upon the activities of WBC, which originate in the bone marrow. -lymphatic system, lymph Pluripotent hemaropoietic stem cell in bone marrow gives rise to all the cellular element of blood. WBC lymphoid and myeloid lineages. The myeloid lineage comprises most of the cells of the innate immune system. Precisely, the common myeloid progenitor is the precursor of the macrophages, granulocytes and dendritic cells. Common myeloid progenitor macrophages Dispose of pathogens and infected cells, reduce inflammation and clear debris granulocytes to have a role Most numerous, most important in innate immune response in the defense against parasitesneutr ophils basophils -involvement in allergic reactions, rather damaging; thought eosinophils dendritic cells Monocytes are the precursors of macrophages. Macrophages perform important functions as part of the immune response by disposing of pathogens and infected cells. Macrophages also play a role in orchestrating immune response, by helping reduce the inflammation. Finally, macrophages act as scavenger cells in the body, clearing dead cells and cell debris. Granulocytes: neutrophils, eosinophils, basophils. Granulocytes are so called because they have densely staining granules in their cytoplasm; they are also called polymorphonuclear Cristina Mitric ----- Janeways Immunobiology ----- Chapter 1 leukocytes because of their oddly shaped nuclei. The three different types are due to the different staining properties of the granules. In comparison to macrophages they are short-lived, surviving only a few days, and are produced in increased numbers during immune responses, when they leave the blood to migrate to sites of infection or inflammation. Neutrophils are the most numerous and play the most important role in innate immune responses: they take up a variety of microorganisms by phagocytosis and efficiently destroy tem n intracellular vesicles using degradative enzymes and other antimicrobial substances stored in the cytoplasmic granules. Mast cells, whose blood-borne precursors are not well defined, play a role in orchestrating allergic responses, and are thought to play a part in protecting the internal surfaces of the body against pathogens and are involved in the response to parasitic worms. Dendritic cells take up particulate matter by phagocytosis and continually ingest large amounts of the extracellular fluids and its contents by a process known as macropinocytosis. The main role of dendritic cells that have encountered invading microorganisms is to develop into cells capable of activating T lymphocytes by displaying pathogen antigens on their surface so that they can be recognized and responded to by T cells.However, recognition of antigen alone is not sufficient to activate a T lymphocyte that has never encountered its antigen before. Mature dendritic cells have additional properties that enable them to activate T lymphocytes (co-stimulatory factors). Cells that can present antigens to inactive T lymphocytes and activate then for the very first time are known as Antigen-resenting cells APC, and such cells form a crucial link between the innate immune response and the adaptive immune response. Macrophages can also act like antigen-presenting cells, and they are important in particular situations. Dendritic cells however, are the cells that specialize in presenting antigens to lymphocytes and initiating adaptive immune responses. Who does phagocytosis? -macrophages, monocytes, neutrophils, dendritic cells. Lymphoid lineage: Natural killer cells NK (innate immune system) able to recognize and kill some abnormal cells, for example some tumor cells and cells infected with herpes viruses. Lymphocytes (adaptive immune system): T cells and B cells antigen-specific -huge repertoire of receptors that are highly diverse in their antigen-binding sites -small when nave/inactive (no infection), large when functional- effector/active Originate Mature Proliferate and differentiate into in in B Bone Bone cells marrow marrow Plasma Cells Produce antibodies; immunoglobulins (mIg Both B cells or sIg) and T cells migrate T Bone Thymus from their site cells marrow RegulateSu Kill Cells infected with of mauration ppress the viruses or other through the activity of intracellular pathogens bloodstreamto other the peripheral lymphocyte lymphoid organs. s and help control immune responsesA dditionalCristina Mitric ----- Janeways Immunobiology ----- Chapter 1 signals: activate antigen- stimulated B cells; increase phagocytic activity of macrophage sCytotoxic T cells Regulatory T cells Activate Helper T cells During the course of an immune response, some of the B cells and T cells activated by antigen differentiate into memory cells, the lymphocytes that are responsible for the long-lasting immunity that can follow exposure to disease or vaccination. Memory cells will readily differentiate into effector cells on a second exposure to their specific antigen. *Antibodies= secreted form of the B-cell receptor and have an identical antigen specificity. =Immunoglobulins (Ig); the antigen receptor of B lymphocytes is also known as membrane immunoglobulin (mIg) or surface immunoglobulin (sIg) Lymphoid tissues/organs = organized aggregates of lymphocytes in a framework of nonlymphoid cells. central/primary
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