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Biology 201 Fundamentals of Biology II

Biology 201 Fundamentals of Biology II. Rob Mustard Adjunct Faculty. PALOMAR COLLEGE. Leukocytes & Immune Response. Blood cells are one of the “fluid” Connective Tissues Red blood cells (erythrocytes) Mammalian RBCs lack nuclei and mitochondria ~7  m diameter

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Biology 201 Fundamentals of Biology II

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  1. Biology 201Fundamentals of Biology II Rob Mustard Adjunct Faculty PALOMAR COLLEGE PALOMAR COLLEGE

  2. Leukocytes & Immune Response Blood cells are one of the “fluid” Connective Tissues Red blood cells (erythrocytes) Mammalian RBCs lack nuclei and mitochondria ~7 m diameter White blood cells(leukocytes) Giemsa stain to differentiate WBCs 6-7 million erythrocytes / ml3 7,000 leukocytes / ml3 PALOMAR COLLEGE

  3. Immune Response Modes Innate Immunity Rapid (and general) response to a broad range of microbial invasion Acquired (Adaptive) Immunity Secondary (and highly-specific) response to previously-encountered pathogens Vertebrates have both forms of immune-response mechanisms PALOMAR COLLEGE

  4. Innate Immunity External defenses include: Skin: impenetrable to most viruses & bacteria Mucous: viscous fluid that traps microbes Cellular secretions: sebaceous (oil) & sweat glands reduce skin’s pH to 3-5; lysozyme digests Gram + cell walls Internal defenses begin after bacteria invade, typically through a break in skin or other epidermal layer PALOMAR COLLEGE

  5. Inflammatory Response Tissue damage from physical injury leads to cascade of chemical signals Histamine, stored in mast cells in connective tissue Nearby capillaries become dilated and leaky, allowing passage of macrophages and increased blood flow Increased local blood supply leads to redness, heat and swelling (inflammation) Macrophages move out into damaged tissues, in interstitial spaces between cells Nonspecific Inflammatory Response PALOMAR COLLEGE

  6. Leukocytes Involved in Innate Immunity: Phagocytes Neutrophils 60-70% of all leukocytes, live only a few days Big: 12-15 m (2x erythrocytes) Nucleus has 2-5 lobes (polymorphic) Monocytes 5% of all leukocytes Biggest: 20 m Lighter, “frothy” horseshoe-shaped nucleus Neutrophils are granular Monocytes are agranular PALOMAR COLLEGE

  7. Leukocytes Involved in Innate Immunity: Phagocytes Eosinophils Rare in blood smears (2-4%) Big: 12-15 m (same size as Neutrophils) Nucleus has 2 lobes Dendritic Cells Patrol interstitial spaces of skin & mucosal membranes Phagocytize invaders, process & present antigen material (APCs) Activate acquired immune system Eosinophils are granular PALOMAR COLLEGE

  8. Leukocytes Involved in Innate Immunity: Hypersensitivity Basophils Rarest of the leukocytes (<0.5%) 10-12 m diameter Respond to allergic reactions (e.g., bee & wasp stings, pollen) Very granular; nucleus often obscured Live for about 2 weeks Basophils are very granular PALOMAR COLLEGE

  9. Leukocytes Involved in Innate Immunity: Cytotoxicity Natural Killer Cells A specialized lymphocyte Attack virus-infected cells Attack cancer cells (tumors) NK cells recognize infected/defective cells via surface features Bind to target cells, release chemicals (perforins) that lead to apoptosis An NK cell (N) attached to a "target" cell "T". The NK cell will kill the now helpless target cell quickly, by the injection of deadly perforin. PALOMAR COLLEGE

  10. Leukocytes Involved in Acquired Immunity Lymphocytes Very common in blood; 20-40% of WBCs Slightly larger than RBCs (~10 m) Dark-staining, circular nucleus Agranular; cytoplasm is transparent PALOMAR COLLEGE

  11. Lymphocyte Specialization Vertebrate lymphocytes take on specialized roles Circulate through blood & lymph, concentrated in spleen & lymph nodes B & T cells bear ~100K antigen receptors (all the same) Antigen- binding sites IgM Receptors V V Variable regions V Light chain V V V C C C C C C Constant regions b chain Heavy chains  chain PALOMAR COLLEGE T cell B cell

  12. Acquired Immunity Responses Humoral Response Dendritic cell (APC) engulfs pathogen, presents antibody via cell-surface protein (MHC class II) Helper T cell binds to presented antigen APC releases cytokines to stimulate production of more “activated” T cells Activated B cells secrete antibodies, which immobilize pathogens, marking them for destruction by macrophages Cellular Immune Response A cell other than a leukocyte takes up and kills a microbe, presents antigen on surface (MHC class I) Cytotoxic (activated) T cell binds to presented antigen, releases perforins, lyses infected cell PALOMAR COLLEGE

  13. Questions?? PALOMAR COLLEGE PALOMAR COLLEGE

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