Final answer:
CD4 is not produced by T follicular helper (TFH) cells; it is a surface glycoprotein on helper T cells, including TFH cells, and not a cytokine or secreted product. TFH cells secrete cytokines such as IL-4, IFN-gamma, TNF-alpha, and IL-21. The correct option is 1) CD4
Step-by-step explanation:
The question asks which of the following is not produced by T follicular helper (TFH) cells: CD4, IL-4, IFN-gamma, TNF-alpha, or IL-21. T follicular helper cells are a subset of helper T cells that play a crucial role in the immune system by helping B cells produce antibodies.
Specifically, TFH cells are not responsible for producing CD4 because CD4 is a glycoprotein expressed on the surface of helper T cells, including TFH cells, rather than a product of these cells. Instead, CD4 acts as a co-receptor that enhances the activation of T cells by binding to MHC class II molecules on the surface of antigen-presenting cells.
TFH cells are known to secrete a variety of cytokines, including IL-4, IFN-gamma, TNF-alpha, and IL-21, which assist in various immune responses, such as B cell differentiation and antibody production. The correct option is 1) CD4