Summary

Helper T-cells are a type of T-cells in the adaptive immune system that work by coordinating the actions of other immune cells against a specific antigen. Specifically, they use chemical signals called cytokines to tell other cells what to do in response to a threat. Helper T-cells are identified by their expression of CD4, which distinguishes them from other types of T-cells. This CD4 is also responsible for recognizing MHC II, an antigen-presenting complex found exclusively on antigen-presenting cells (APC). Once activated to a threat (specific antigen), helper T-cells then differentiate into effector subtypes (including Th1, Th2, and Th17), depending on the type of antigen presented. The effector subtype determines what cytokines the active Helper T-cell will eventually produce.

Key Points

• Helper T Cells (Th Cells)
  • Subtype of T-lymphocytes in the adaptive immune system
  • Express CD4 (also known as CD4+ T-cells)
  • Recognize antigens bound to MHC II
    • Via T-cell receptors (TCR) with the help of CD4
  • Stimulated by Interleukin-2 (IL-2)
    • IL-2 stimulates growth of all lymphocytes, including T-cells
  • After T-cell Activation, differentiate into effector subtypes depending on antigen presented:
    • Th1 cells
    • Th2 cells
    • Th17 cells
  • Primary target in HIV infection