CD4+ T Cells and Antitumor Immunity - Th1 and Th2 CD4+T Cells

Th1 and Th2 CD4+T Cells

The same series of experiments, examining the role of CD4+ cells, showed that high levels of IL-4 and IFNγ were present at the site of the tumor, following vaccination, and subsequent tumour challenge. (Hung, 1998) IL-4 is the predominant cytokine produced by Th2 cells, while IFNγ is the predominant Th1 cytokine. Earlier work has shown that these two cytokines inhibit the production of each other by inhibiting differentiation down the opposite Th pathway, in normal microbial infections, (Abbas and Lichtman, 2005) yet here they were seen at nearly equal levels. Even more interesting was the fact that both these cytokines were required for maximal tumor immunity, and that mice deficient in either showed greatly reduced antitumor immunity. IFN-γ mice showed virtually no immunity, while IL-4 mice showed a 50% reduction when compared to immunised wildtype mice.

The reduction of immunity in IL-4 deficient mice, has been attributed to a decrease in eosinophil production. In mice deficient in IL-5, the cytokine responsible for differentiation of myeloid progenitor cells into eosinophils, less eosinophils are seen at the site of tumour challenge, which is to be expected. (Hung, 1998) These mice also show reduced antitumor immunity, suggesting that IL-4 deficient mice, which would produce less IL-5, and subsequently have reduced eosinophil levels, elicit their effect through eosinophils.