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immunology

Chapter 14 Adaptive Immune Response in Space and Time Dr. Capers. immunology. Invaders infect our bodies Cells of innate immune system arrive first Adaptive immune response provides longer protection Leukocytes are constantly monitoring for infection

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immunology

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  1. Chapter 14 Adaptive Immune Response in Space and Time Dr. Capers immunology

  2. Invaders infect our bodies • Cells of innate immune system arrive first • Adaptive immune response provides longer protection • Leukocytes are constantly monitoring for infection • When detected, cells cross the blood barrier and travel to site of infection

  3. Naïve Lymphocytes • After 30 minutes of entering in bloodstream, they enter into the spleen • Browse for approximately 5 hours • Then they go to the peripheral lymph nodes • Stay for 12-18 hours • Do they find their antigenic match? The chances are very low • Remember we make millions of B and T cells with their own specificity, most are not needed/used

  4. Our tissues are held together by molecular interactions • Cell adhesion molecules (CAMs) • Selectins, mucins, integrins, Ig-Superfamily CAMs (ICAMs) • Can be used by leukocytes to interact with tissues • For leukocytes to enter inflamed tissues, cells must adhere and pass between endothelial cells lining blood vessel - EXTRAVASATION • Endothelial cells can express certain leukocyte specific CAMs

  5. Chemokines • Major regulators of leukocyte traffic • Cytokines that are responsible for movement of immune cells • Small polypeptides • Some involved in inflammation, some involved in homeostatic roles (“house keeping”) • Induce adherence of leukocytes to endothelial lining

  6. Chemokines • Chemokine receptors on leukocytes mediate leukocyte activity

  7. Lymphocyte (B and T cells) Recirculation • Unlike other leukocytes, lymphocytes recirculate continuously from blood to tissues to lymph (1 to 2 times a day) • Lymphocytes are antigenically committed • This recirculation increases chances of lymphocyte coming into contact with particular antigen

  8. Lymphocyte (B and T cells) Extravasation • Involves interaction of CAMs • Ensures proper populations of B and T cell make it into certain tissues • HEVs – high endothelial venules • Post capillary areas in secondary lymphoid tissue • Areas that have cells that are more cubodial in shape • Express variety of CAMs • Helps the B and T cells migrate into the lymphoid tissues

  9. Lymphocyte Extravasation

  10. Lymphocyte Extravasation

  11. Although lymphocyte extravasation is similar to neutrophils, different subsets of lymphocytes must make it into different tissues • Naïve lymphocytes • Migrate to secondary lymphoid tissue to encounter antigen • Effector and memory lymphocytes • Home to regions of infection • Memory cells will tend to home to tissues in which they first encountered antigen

  12. APCs at the site of infection engulf antigen and present in MHC Class II • They upregulate chemokine receptors that allow them to travel to lymph nodes • Present it to T cells that are there • Some antigen travels directly to the lymph node, coming into contact with B cells that are there that then present to the T cells

  13. Activation of TH cells and B cells in the lymph node during primary response

  14. B cell activity in germinal center (proliferation, hypermutation, class switching)

  15. The differentiation of naïve lymphocytes into effector cells takes place over the first 4-7 days of the response during the primary response

  16. Lymphocyte activation and expansion are followed by dramatic contraction • 95% of the lymphocytes die • Pro-apoptotic and antiproliferative influence

  17. 3 types of memory cells populate different regions of the body • Effector memory cells circulate • Resident memory cells take up residence in various tissues • Central memory cells stay in secondary lymphoid tissue

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