Salvalaggio Paolo R O, Camirand Geoffrey, Ariyan Charlotte E, Deng Songyan, Rogozinski Linda, Basadonna Giacomo P, Rothstein David M
Department of Surgery, Yale School of Medicine, New Haven, CT 06510, USA.
J Immunol. 2006 Feb 15;176(4):2292-8. doi: 10.4049/jimmunol.176.4.2292.
The role of CTLA-4 in tolerance is primarily inferred from knockout and blocking studies. Anti-CD45RB mediates allograft tolerance in mice by inducing CTLA-4 expression on CD4 cells, providing a novel opportunity to determine how therapeutic enhancement of CTLA-4 promotes tolerance. We now show that induced CTLA-4 expression normally resolves by day 17. Although thymectomy prolongs enhanced CTLA-4 expression, long-term engraftment is unaffected. To address the temporal relationship between increased CTLA-4 expression and engraftment, transplantation was delayed for various times after anti-CD45RB treatment. Delaying transplantation for 7 days (when CTLA-4 expression had peaked but treatment mAb was no longer detectable), resulted in long-term engraftment comparable to transplantation with no delay (day 0). Delaying transplantation from 10 to 18 days led to a progressively poorer outcome as CTLA-4 expression returned to baseline. This suggested that Ag exposure while CTLA-4 expression is enhanced is sufficient to induce long-term engraftment. To substantiate this, on day 0, anti-CD45RB-treated mice received BALB/c vs unrelated alloantigen, followed by transplantation of BALB/c islets 10 days later. Whereas recipients exposed to unrelated Ag experienced acute rejection, recipients exposed to donor Ag achieved long-term engraftment. Anti-CD45RB-treated mice exposed to alloantigen exhibited anergic CD4(+)CD25(-) effector cells and regulatory CD4(+)CD25(+) cells. Moreover, CD25 depletion in the peritransplant period prevented anti-CD45RB-mediated engraftment. Thus, exposure of CD4 cells expressing CTLA-4 to donor Ag is necessary and sufficient to induce long-term engraftment which appears to be mediated by both regulation and anergy.
CTLA-4在免疫耐受中的作用主要是通过基因敲除和阻断研究推断出来的。抗CD45RB通过诱导CD4细胞上CTLA-4的表达介导小鼠同种异体移植耐受，这为确定CTLA-4的治疗性增强如何促进耐受提供了新的机会。我们现在发现，诱导的CTLA-4表达通常在第17天消失。虽然胸腺切除术延长了增强的CTLA-4表达，但长期植入不受影响。为了研究CTLA-4表达增加与植入之间的时间关系，在抗CD45RB治疗后不同时间延迟移植。将移植延迟7天（此时CTLA-4表达已达到峰值，但治疗性单克隆抗体已无法检测到），导致长期植入与无延迟移植（第0天）相当。将移植从第10天延迟到第18天，随着CTLA-4表达恢复到基线，结果逐渐变差。这表明在CTLA-4表达增强时接触抗原足以诱导长期植入。为了证实这一点，在第0天，用抗CD45RB治疗的小鼠接受BALB/c与无关同种异体抗原，然后在10天后移植BALB/c胰岛。暴露于无关抗原的受体经历急性排斥反应，而暴露于供体抗原的受体实现了长期植入。暴露于同种异体抗原的抗CD45RB治疗小鼠表现出无反应性的CD4(+)CD25(-)效应细胞和调节性CD4(+)CD25(+)细胞。此外，移植期周围的CD25耗竭阻止了抗CD45RB介导的植入。因此，表达CTLA-4的CD4细胞暴露于供体抗原是诱导长期植入的必要和充分条件，长期植入似乎是由调节和无反应性共同介导的。
