Much or our understanding of the signaling events initiated in T cells responding to antigen comes from studies of transformed T cell lines in culture. But now several lines of evidence indicate that freshly isolated T cells from mice may respond rather differently. Zell et al. therefore developed methods to analyze responses of CD4+ T cells collected from lymph nodes or spleens. They used flow cytometry and antibodies that specifically recognized the phosphorylated, active form of the c-Jun NH2-terminal kinase (JNK) to measure responses of single cells exposed to antigen in the whole animal. Responses differed from those in cultured cells in that the untransformed T cells responded more rapidly and more efficiently, phosphorylation of c-Jun or the p38 mitogen-activated protein kinase did not require activation of the costimulatory receptor CD28, and the immunosuppressive drug cyclosporin A did not inhibit phosphorylation of the MAP kinases. The authors caution that the microenvironment to which the T cells are exposed in the animal appears to modulate the characteristics of signaling substantially from those observed in cultured cell lines.
T. Zell, A. Khoruts, E. Ingulli, J. L. Bonnevier, D. L. Mueller, M. K. Jenkins, Single-cell analysis of signal transduction in CD4 T cells stimulated by antigen in vivo. Proc. Natl. Acad. Sci. U.S.A. 98, 10805-10810 (2001). [Abstract] [Full Text]