Learning Objective:
Understand the concept of lymphocyte anergy, its mechanism, and its role in peripheral tolerance.
Definition:
- Anergy is a state of unresponsiveness in which a lymphocyte cannot be activated by its specific antigen.
Mechanism:
- T and B cells become anergic if they encounter antigen without the required costimulatory signal (signal 2).
- T cells: Signal 1 = TCR + MHC, Signal 2 = CD28 + B7 (CD80/86)
- B cells: Signal 1 = BCR + antigen, Signal 2 = CD40 + CD40L
Role in Immune Tolerance:
- Prevents autoimmunity by inducing peripheral tolerance when self-antigens are encountered outside the thymus or bone marrow.
High-Yield Step 1 Tip:
- Anergic T cells → cannot proliferate or secrete cytokines upon antigen encounter.
- Anergic B cells → fail to produce antibodies or undergo class switching.
