Azathioprine and 6-mercaptopurine (6-MP) suppress the human mixed lymphocyte reaction (MLR) by different mechanisms.

Abstract

6‐MP inhibitory effects on the MLR were reversed by AIC (46%), adenine (32%), hypoxanthine (89%), adenosine (86%) and inosine (93%). AIC, adenine, hypoxanthine and inosine had no effect on azathioprine inhibition of the MLR. Adenosine at 10 microM caused 29% reversal and had no effect at 100‐400 microM on azathioprine inhibition of the MLR. Reversal of 6‐MP suppression of the MLR was decreased with the delay of adenosine addition. Guanine, xanthine and guanosine caused no reversal of 6‐MP or azathioprine inhibitory effects on the MLR. These results show that azathioprine and 6‐MP suppress the MLR by different mechanisms.