Final answer:
IL-4 is induced in a CD4 TH2 cell by the transcription factor GATA-3, which is pivotal for the differentiation and function of Th2 cells in humoral immunity.
Step-by-step explanation:
IL-4 is induced in a CD4 TH2 cell under the direction of the transcription factor GATA-3.
Interleukin 4 (IL-4) is a key cytokine in the immune response, playing a crucial role in the differentiation and function of T helper 2 (Th2) cells. During the activation of Th2 cells, different transcription factors are responsible for directing the expression of various cytokines. In particular, GATA-3 is the main transcription factor involved in the induction of IL-4 in CD4+ helper T cells. When a CD4+ helper T cell interacts with an antigen-presenting cell, it can differentiate into a Th2 cell under the influence of certain cytokines, such as those secreted by activated antigen-presenting cells. Th2 cells are critical for the immune response as they help in the activation of B cells and promote antibody responses.
The differentiation process of activated helper T cells into Th2 cells, which involves GATA-3, is influenced by signals and cytokines such as those from antigen-presenting cells. These cells release cytokines upon interaction with a helper T cell presenting an antigen bound to MHC II molecules. Activated Th2 cells, in turn, secrete cytokines like IL-4, which promote B cell differentiation into antibody-secreting plasma cells, thus fostering humoral immunity. Moreover, Th2 cells can influence the activity of other immune cells, such as mast cells, through the secretion of cytokines.