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Cells and Organs of The Immune System ((Trap antigen from tissue or…

- - - - Red Pulp : sites where defective red blood cells are destroyed by macrophage
      - White Pulp : populated mainly by T lymphocytes
    - - Peyer's Patches : contained in the submucosal layer beneath lamina propia
      - Peyer's patches can develop into secondary follicles with germinal centers
      - Lamina Propia : contain large number of B cells, plasma cells, activated Th cells and macrophages
    - - -Germinal centers develop in response to antigenic stimulation
        
        -Primary follicles contain mature & naive B lymphocytes,
        
        -Follicles are the B cells zone of lymph nodes,
        
        -sites of remarkable B cell proliferation, generation of memory B cells
        
        -most of CD4+ helper T cells located in the cortex
        
        -Dendritic cells concentrated in T cells zone
- - - - sites where immature B cells proliferate & differentiate, stromal cells within bone marrow interact with B cells & secretes cytokines
    - - Cortex : Densely packed with immature T cells (thymocytes)
        Medulla : sparsely populated with thymoctes
- - - - B cells differentiates over 4-5 day period generating population of plasma cells and memory cells.
- - - - activated when they interact with an antigen–class I MHC complex on the surface of an altered self-cell
    - - activated by recognition of an antigen–class II MHC complex on an antigen-presenting cell.
- - - - major type that involved in initiating T cell responses is dendritic cells.
        
        dendritic cells are found under epithelia and in most organs. they capture antigens and transport to peripheral lymphoid organs.
        
        4 types of dendritic cells: Langerhans cells, interstitial dendritic cells, myeloid cells and lymphoid dendritic cells.
        
        derived from monocyte lineage and are called myeloid dendritic cells.
        
        MONOCYTE
        
        First cell to enter peripheral blood after leaving marrow and is incompletely differentiated.
        
        10-15um diameter and have bean-shaped nuclei and finely granular cytoplasm containing lysosomes,phagocytic vacuoles and cytoskeletal filaments.
        
        once they settled in tissues, they mature and become macrophages.
        
        in the central nervous system, they are called microglial cells, when lining the pulmonary they are called alveolar macrophages, when lining the vascular sinusoids of the liver they are called Kupffer cells and in multinucleated phagocytes in bone they are called osteoclasts.
        
        containing ingested microbes display microbial antigens to differentiated effector T cells.
      - macrophages present antigens to T cells during cell-mediated immune response.
      - B lymphocytes functions as APC for helper T cells during humoral response.
- - - - -can be found in many type of tissues
        
        -have large numbers of cytoplasmic granules, which contain histamine and other active substances
        
        -mast cell with blood basophils, play an important role in the development of allergies
    - - -involve in immune defenses against viruses and tumors
        
        -influence both innate and adaptive immunity
        
        -cytoplasm of NK cellshave numoerous granules containing perforin and granzymes
        
        Release of perforin and granzymes involved in NK-mediated killing or target cells byy apoptosis
        
        -produce IFN-, effect the participation of macrophages in innate immunity by activation of phagocytic and microbicidal activities
    - - -motile phagocytic cells, can migrate from blood into tissue spaces
        
        -less significant than nuetrophils, but play role in defense against parasitic organisms
        
        secreted contents of eosiphilic granules may damage the parasite membrane
    - - -when cells active, can secrete hydrolytic enzymes in the lysosomes of the macrphages
        
        -contributes to the inflammatory response, some cases can contribute to extensive tissue damage
        
        -activated macrophages secrete soluble factors, eg: TNF-, can kill variety of cells
        
        -contribute to tumor destruction
    - - -produced by hematopoiesis in the bone marrow
        
        -the first to arrive at a site of inflammation
        
        -active phagocytic cells, same to macrophages
        
        -primary and secondary granules containlytic enzymes and bactericidal substances
        
        -both primary & secondary granules fuse with phagosome, that contents are then digested and eliminated