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

2. PALOMAR COLLEGE Leukocytes & Immune Response Blood cells are one of the “fluid” Connective Tissues Blood cells are one of the “fluid” Connective Tissues Red blood cells (erythrocytes) Red blood cells (erythrocytes)  Mammalian RBCs lack nuclei and mitochondria  ~7  m diameter White blood cells (leukocytes) White blood cells (leukocytes)  Giemsa stain to differentiate WBCs 6-7 million erythrocytes / ml 3 7,000 leukocytes / ml 3

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

4. PALOMAR COLLEGE Innate Immunity External defenses include: 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 Internal defenses begin after bacteria invade, typically through a break in skin or other epidermal layer

5. PALOMAR COLLEGE Inflammatory Response Tissue damage from physical injury leads to cascade of chemical signals 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 Nonspecific Inflammatory Response Nonspecific Inflammatory Response

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

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

8. PALOMAR COLLEGE Leukocytes Involved in Innate Immunity: Hypersensitivity Basophils 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

9. PALOMAR COLLEGE Leukocytes Involved in Innate Immunity: Cytotoxicity Natural Killer Cells 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.

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

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

12. PALOMAR COLLEGE Acquired Immunity Responses Humoral Response 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 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

13. PALOMAR COLLEGE Questions??