Final answer:
Cells that leave the thymus and can bind to class II MHC molecules develop into helper T cells, which are crucial in supporting the immune response by activating B cells and stimulating other immune activities.
Step-by-step explanation:
The cells that leave the thymus and have the ability to bind to class II major histocompatibility (MHC) molecules develop into helper T cells. The CD4+ T cells, which are also known as helper T cells, recognize and bind to class II MHC molecules presented on the surface of professional antigen-presenting cells, such as macrophages, dendritic cells, and B cells. These helper T cells play a crucial role in the immune response by assisting in the activation of B cells, which produce antibodies, and supporting other immune responses.
Moreover, CD8+ cells, or cytotoxic T cells, bind to class I MHC being expressed on nearly all cells in the body. It is the CD4+ T cells that specifically interact with class II MHC, defining their role as helper T cells in the immune system. Through the release of cytokines, these helper T cells play a significant role in orchestrating various immune responses, including the activation of macrophages and the stimulation of B cells to produce antibodies.