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Ch. 45

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Rutgers University
Biological Sciences

Ch. 45 The Immune System: Internal Defense Vertebrate Defense -- Non-specific (Fig 45-1) Cytokines and Chemokines • Signaling proteins and peptides produced mainly by macrophages, fibroblasts, NK cells and T-cells • Interferons type 1 (aloha) and type 2 (gamma) raised in response to certain viruses, cancers Tumor necrosis factor (TNF) secreted in response to gram negative bacteria, cancer • cells and various pathogens; initiates inflammatory response • Interleukins and chemokines are produced mainly by macrophages and lymphocytes to help regulate interactions with other body cells (Signal cascade) ← Inflammatory Process (Fig 45-3) Vertebrate Defense -- specific (Fig 45-1) • Cell-mediated • Specific T cells mature in thymus gland, stored in spleen lymph nodes, tonsils, and lymph tissues Include cytotoxic T cells (CD8) and helper T cells (CD 4) and memory cells • • Antibody-mediated • Specific B cells mature in adult bone marrow; stored in bone marrow, spleen and lymph nodes • When activated, B cells differentiate into plasma cells (that produce antibodies - IgM and then IgG), as well as memory cells ← All cells involved in specific immunity some from the bone marrow (Fig 45-5) • NK cells are specialized lymphocytes: active against virally- infected and cancer cells. Release perforins, and then granzymes with cytokines induce cellular apoptosis ← T Lymphocytes • Mature in the thymus gland where they become immunocompetent: • Self selection means mature only if recognize their own antigens (TCR, MHC) as “self” • T cells that recognize self-antigens as foreign are apoptosed If thymus removed during first months of life- no mature T-cells and no immunity • ← Cells involved in specific immunity express MHC antigens • Class 1: expressed on surface of all nucleated cells: MHC 1 presents intracellular, digested proteins to Tc-Cells (CD8) - endogenous pathway • Class 2: expressed only on “APC” cells (B-cells, macrophages, dendritic): MHC 2 presents endocytosed fragments to Th (CD4) cells; immune cascade - exogenous pathway • Class 3: include soluble complement proteins, inflammatory cytokines, TNF and heat- shock proteins - secretory pathway ← Tc cells, MHC 1 are involved in Cancer Cell Destruction (Fig 45-13) •Tc cells recognize cancer cells as non-self due to MHC 1 display of altered or unique antigens on transformed cell surface Tc cells (with NKC) chemically attack cancer cell (granzymes, perforins and cytokines) • breaking down its PM •Cancer cell is destroyed leaving a collapsed fibrous cytoskeleton (apoptosis) • BUT: MHC1 down regulation; unique antigens Bacterial infections stimulate the Th, MHC 2 pathway (Fig 45-6) •Exogenous pathogen (bacteria) invades body tissue •APC digests bacterial proteins to peptides •Bacterial peptides plus MHC 2 protein displayed on APC cell surface (IL 1 released) •Th (CD4) are activated, clonally e
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