Helper cells belong to

1. CD4+ T cells: CD4 cells are also known as helper T (Th) cells. They constitute about 65% of peripheral T cells and are found mainly in the thymic medulla, tonsils, and blood. CD4 displayed on the surfaces of these T cells recognize a nonpeptide-binding poion of MHC class II molecules. Hence, CD4+ T cells are restricted to the recognition of MHC class II complexes. Helper T lymphocytes are involved in the induction and regulation of immune responses. 2. Main function of helper T cells: 1. Help in the antigen-specific activation of B cells and effector T cells. 2. Th-1 cytokines activate cytotoxic inflammatory and delayed hypersensitivity reactions. 3. Th-2 cells help in the production of interleukins which encourage production of antibodies especially IgE. 4. Th-2 cytokines are associated with regulation of strong antibody and allergic responses.