Final answer:
Cytokines produced from proliferated T cells do stimulate CTL differentiation, a fact that is critical for the efficacy and longevity of the immune response. These cytokines serve as autocrine or paracrine factors and are secreted by a variety of cells, including immune cells.
Step-by-step explanation:
The statement that cytokines produced from proliferated T cells stimulate CTL differentiation is true. Proliferation and differentiation of cytotoxic T cells (CTLs) are indeed stimulated by cytokines secreted by helper T cells (Th1 cells). These helper T cells are activated by the same foreign antigen epitope and provide co-stimulation through the secretion of cytokines. Although cytotoxic T cells can be activated without this stimulation from Th1 cells, their activation in such cases is generally less effective or durable.
There is a wide range of cytokines, and they are glycoproteins secreted by various cells like leukocytes, macrophages, and others, functioning as autocrine or paracrine factors. In addition to stimulating the proliferation of CTLs, they also play a crucial role in stimulating both nonspecific and specific resistance to disease.
In summary, cytokines secreted by T cells help in the proliferation and differentiation into functional cells such as CTLs and plasma cells, which are fundamental elements of the immune response.