How do cytokines affect the humoral immune response?
1 Answer
IL4 and IL5 secreted by TH2 helper T cells act on a naive B cell to elicit a humoral immune response.
Just to be clear, humoral immune responses are those that are mediated by secreted antibodies, which are immunoglobulins by nature. Also, B cells are the only cell type that can manufacture antibodies.
The B cells, upon making contact with TH2 cells and under the influence of interleukins 4 and 5, undergo maturation, proliferation and differentiation. They differentiate into Plasma cells (which manufacture and secrete antibodies) and Memory B cells (long lived, quiescent B cells that can be mobilized when its antibody is required in the future). These cytokines can also induce 'class switching'. B cells start out expressing IgM, then IgM+IgD. Class switching enables the B cells to produce other classes of immunoglobulins, such as IgG, IgE and IgA.
This is just a basic answer. There are many other cytokines that act either directly on B cells, or regulate T helper cells. This indirectly influences the rate of production and type of antibody produced.
The next question is, what do these secreted antibodies do? They help eliminate pathogens by activating the 'complement system' and tag pathogens for phagocytosis, all coordinated by cytokines. It is very difficult to see Innate and Humoral Immunity as separate processes because they is so much interplay between them.
Some things to think about:
Which cells produce cytokines?
What are the target cells that have receptors for these cytokines?
What is the downstream (signaling) effect of binding of each cytokine to its cognate receptor?
References:
Cytokine pathways in Immunology
