Final answer:
Colony-stimulating factors are nonspecific mitogens used to stimulate CD4 T cell division. They function by acting as signaling proteins that promote immune cell proliferation when CD4+ helper T cells are activated by antigen-presenting cells.
Step-by-step explanation:
A nonspecific mitogen that is commonly used to stimulate cell division in CD4 T cells is a class of cytokines known as colony-stimulating factors. These are glycoproteins secreted by a variety of cells within the body, including red bone marrow and leukocytes. Their primary role includes acting as autocrine or paracrine factors that promote the proliferation and differentiation of immune cells, including T cells.
In the context of T cell activation, when naive CD4+ helper T cells engage MHC II molecules on antigen-presenting cells, the engagement leads to the activation of the T cells. Following this, both the antigen-presenting cell and the T cell release cytokines, which further stimulates the proliferation of the T cells and helps in mounting a specific immune response.