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 3
Azathioprine treatment induces T cell apoptosis in IBD. (a) LPMCs were isolated and stimulated with anti-CD2/CD28 plus IL-2 in the presence or absence of 6-MP for 5 days followed by FACS analysis. (b) Peripheral blood CD4⁺ T cells were isolated from patients with IBD receiving azathioprine/6-MP and patients with IBD before therapy and stimulated with anti-CD3/CD28 plus IL-2 in the presence or absence of 6-MP for 5 days. The number of apoptotic cells (annexin-positive, propidium iodide–negative cells) was determined by FACS analysis after 5 days and stratified according to clinical data on azathioprine therapy. Data represent mean values ± SEM from eight patients with IBD per group. (c–h) TUNEL assays for the detection of apoptotic lamina propria cells in patients with IBD under azathioprine therapy. Successful azathioprine treatment associated with low-level gut inflammation was characterized by a high number of apoptotic cells (shown at low [d] and high [g] magnification) as compared with control patients with low-level gut inflammation not receiving azathioprine (c and f). In contrast, unsuccessful azathioprine treatment associated with high-level gut inflammation was characterized by a very low percentage of apoptotic cells (e and h). Data are representative of 5–13 patients per group. Magnification, ×20 (bar = 100 μm) (c–e) and ×40 (bar = 50 μm) (f–h). (i) Quantification of the percentage of apoptotic, TUNEL-positive LPMCs in patients with IBD receiving 6-MP as compared with untreated control patients. Clinical 6-MP responsiveness was associated with a marked, significant (P < 0.01) increase in the percentage of apoptotic LPMCs as compared with control patients with IBD not receiving 6-MP. Data are mean values ± SEM of 5–13 patients per group.