Final answer:
The cytokine IL-4 (option b) would be expected to be present during a TH2 cell response, as it's a signature cytokine of TH2 cells, promoting B cell differentiation and IgE antibody production.
Step-by-step explanation:
The cytokine that would be expected to be present during a TH2 cell response is IL-4. TH2 cells, a subset of helper T cells bearing the CD4 molecule, are specialized in providing help to B cells and enhancing antibody production in the immune system. The cytokines they release are different from those released by TH1 cells, which are more involved in cell-mediated immunity and activating infected cell destruction by cytotoxic T cells.
IL-4 is a signature cytokine secreted by TH2 cells, which promotes the differentiation of B cells into plasma cells and the production of IgE antibodies. On the other hand, cytokines like IFN-γ are typically secreted by TH1 cells, while others like TNF-α can be produced by various immune cells in response to inflammation.