Final answer:
After releasing IL-2, helper T cells either differentiate into TH1 or TH2 cells, participate in the immune response, and then die, or become long-lived memory cells that provide immunity to future exposures of the same antigen.
Step-by-step explanation:
Helper T cells play a crucial role as 'managers' in the immune system, especially after they release interleukin-2 (IL-2). Once a CD4+ helper T cell binds to an MHC II-antigen complex on an antigen-presenting cell (APC), it becomes activated and releases cytokines like IL-2. This action propels the immune response forward, with IL-2 specifically stimulating the proliferation and differentiation of immune cells, including helper T cells themselves into various subtypes.
After releasing IL-2, some helper T cells differentiate into either a T helper 1 (TH1) cell, which is involved in cell-mediated immunity, or a T helper 2 (TH2) cell, which is more associated with humoral immunity and activating B cells. Others become memory helper T cells, which are critical for long-term immunity. The effector helper T cells generally perform their immune functions and then die out, completing their role in the immediate immune response. In contrast, the memory helper T cells persist to quickly act upon re-exposure to the same antigen.
The release of IL-2 is a signal for the expansion of the immune response, and once their task is completed, the effector helper T cells undergo apoptosis, while the memory cells remain vigilant for future encounters with the antigen.