Final answer:
Helper T cells (CD4+) are a type of T cell that secrete cytokines to enhance immune responses. There are two classes of Helper T cells, TH1 and TH2, which have different functions in stimulating other immune cells.
Step-by-step explanation:
Helper T (TH) cells, or CD4+ T cells, function by secreting cytokines that enhance other immune responses. There are two classes of TH cells: TH1 and TH2. TH1 cells secrete cytokines to enhance the activities of macrophages and other T cells, while TH2 cells stimulate naïve B cells to secrete antibodies. The differentiation of TH cells into TH1 or TH2 is directed by specific cytokines they are exposed to.