1. Activation of T Lymphocytes
Chapter 9
Activation of T Lymphocytes

3. Activation and effector phases of T cell-mediated adaptive immune responses are triggered by antigen recognition by T lymphocytes
Naive T lymphocytes home to secondary lymphoid organs, where they may encounter antigens presented by mature dendritic cells on class I or class II MHC molecules and thus become activated
Antigen-stimulated T cells that have received both "signal one" through the antigen receptor and "second signals" via co-stimulatory receptors may be induced to secrete cytokines and to express cytokine receptors (like IL-2)
T cell responses decline after the antigen is eliminated by effector cells

4. Activation of Naive and Effector T Cells by Antigen

5. Phases of T Cell Responses

6. SIGNALS FOR T LYMPHOCYTE ACTIVATION

7. The proliferation of T lymphocytes and their differentiation into effector and memory cells require antigen recognition, costimulation, and cytokines

8. Recognition of Antigen
Antigen is always the necessary first signal for the activation of lymphocytes, ensuring that the resultant immune response is specific for the antigen
Activation of naive T cells requires recognition of antigen presented by dendritic cells

9. Role of Costimulation in T Cell Activation

10. Mechanisms of T cell costimulation by CD28

11. The major members of the B7 and CD28 families

12. Role of CD40 in T cell activation

13. The mechanism of therapeutic costimulatory blockade

14. FUNCTIONAL RESPONSES OF T LYMPHOCYTES

15. Changes in surface molecules after T cell activation

16. Cytokines in Adaptive Immune Responses

17. Regulation of IL-2 receptor expression

18. Biologic actions of IL-2

19. Development of Memory T Cells

20. Clonal expansion of T cells

21. Development of memory T cells

22. DECLINE OF T CELL RESPONSES

23. Elimination of antigen leads to contraction of the T cell response, and this decline is responsible for maintaining homeostasis in the immune system
Costimulation and growth factors like IL-2 stimulate expression of the anti- apoptotic proteins Bcl-2 and Bcl-XL in the activated lymphocytes, and these proteins keep cells viable
The inhibitory receptors CTLA-4 and PD-1, apoptosis induced by death receptors of the TNF receptor superfamily (such as TNFRI and Fas), and regulatory T cells