CD28-dependent Rac1 activation is the molecular target of azathioprine in primary human CD4⁺ T lymphocytes
J. Clin. Invest. Imke Tiede, et al. 111:1133 doi:10.1172/JCI16432 [Go to this article.]

Figure 2
(a) Peripheral blood CD4⁺ T cells from healthy volunteers were stimulated with antibodies to CD3 and CD28 and recombinant IL-2 and cultured in the presence or absence of 6-MP and 6-TG for 4–5 days. T cell apoptosis was assessed by FACS analysis (upper panels). The average level of 6-MP– and 6-TG–specific apoptosis (induction of annexin-positive, propidium iodide–negative T cells compared with untreated cells) ± SEM from four independent experiments is shown in the lower panel. (b) Kinetics of azathioprine-induced apoptosis in primary CD4⁺ T lymphocytes. CD4⁺ T cells were cultured in the presence or absence of azathioprine for 2–5 days as indicated. T cell apoptosis was assessed by FACS analysis at the indicated time points. (c) 6-MP suppresses clonal expansion of activated primary CD4⁺ T lymphocytes in cell culture. CD4⁺ T cells were cultured in the presence (+) or absence (–) of 6-MP for 3–5 days. The clonal expansion of T cells during cell culture was calculated as specified in Methods. (d) CD4⁺ T cells were cultured in the absence of azathioprine or 6-MP for 5 days, followed by addition of azathioprine or 6-MP to the cell culture for an additional 5 days. The percentage of annexin-positive, propidium iodide–negative cells was then determined at day 10 by FACS analysis. The average percentage of azathioprine- and 6-MP–specific apoptosis (induction of annexin-positive, propidium iodide–negative cells compared with untreated cells indicated by black sections of bars, induction of annexin-positive, propidium iodide–positive cells compared with untreated cells indicated by white sections) ± SEM is shown in the lower panel.