Final answer:
Helper T cells express the CD4 receptor and are thus referred to as CD4+ T cells. They play a crucial role in aiding the immune response by releasing cytokines, in contrast to CD8+ T cells, which are cytotoxic and kill infected cells.
Step-by-step explanation:
The type of CD+ helper cell is CD4. Helper T cells, also known as TH cells, express the CD4 receptor on their surface. In contrast, the CD8 receptor is expressed by cytotoxic T cells (Tc), which play a different role in the immune response.
Cell signals in the thymus determine which receptor a thymocyte will express, thus differentiating it into either a helper T cell or a cytotoxic T cell. Helper T cells are essential in the immune system as they release cytokines to coordinate the immune response, whereas cytotoxic T cells are responsible for directly killing infected cells.