CD4 cells are pivotal in initiating and regulating the immune response. Upon encountering an antigen-presenting cell displaying an antigen-MHC class II complex, CD4 cells become activated. They then differentiate into various subsets, such as Th1, Th2, Th17, and Treg cells, each producing different cytokines that influence the activity of other immune cells like B cells and cytotoxic T cells.
