Final answer:
Helper T cells identify potential pathogens for other cells of the immune system and stimulate B cell response, while cytotoxic T cells directly kill infected cells. Regulatory T cells suppress inappropriate immune reactions to harmless or self-antigens.
Step-by-step explanation:
Helper T cells play a crucial role in the immune response by identifying potential pathogens for other cells of the immune system. They recognize specific antigens presented by antigen-presenting cells (APCs) through major histocompatibility complex (MHC) class II molecules. Helper T cells can differentiate into different subtypes, such as TH1 and TH2, based on the specific cytokines they are exposed to. These subtypes perform different functions, with TH1 cells enhancing the activities of macrophages and other T cells, and TH2 cells stimulating B cells to secrete antibodies.
Cytotoxic T cells, on the other hand, directly kill infected cells. They recognize specific antigens presented by MHC class I molecules on infected cells and destroy them. Cytotoxic T cells are particularly important in protecting against viral infections, as viruses replicate within cells where they are shielded from circulating antibodies. Once activated, cytotoxic T cells create a large clone of cells with specific receptors to identify infected host cells.
Regulatory T cells are involved in suppressing inappropriate immune reactions to harmless or self-antigens. They play a role in maintaining immune tolerance and preventing autoimmune diseases.