Activation of T Lymphocytes          Chapter 9

   I. Introduction
      A. Recognizing Ag twice
         1. Naive T cells = "resting state"
         2. Activated T cells
         3. Effector T cells & Memory T cells
            a. CD4+ = helper T cells
            b. CD8+ = Cytotoxic T Lymphocytes (CTLs)
      B. Decline

  II. Signals
      A. 1ø
      B. 2ø = costimulators 
            a. costimulation
         1. cell surface
            a. CD28
            b. B7
            c. other receptors
         2. cytokines
            a. IL-2

 III. Activated T cell responses
      A. Cytokines secretion
      B. Proliferation
      C. Differentiation into effector & memory T cells

  IV. Memory T cells
      A. Background
      B. Properties
         1. prolonged survival
         2. respond rapidly
         3. high number
         4. migrate to any tissue
         5. less dependent of costimulation
         6. always undergoing a slow proliferation
         7. generate new effector T cells