Modulation of splenic lymphocyte activities by a new hypoxanthine derivative (ST 789) in immunosuppressed mice.

Splenic lymphocytes of experimentally-immunosuppressed mice of different age (10 weeks and 6 months) were studied to evaluate their functional response following subcutaneous and intraperitoneal treatment with the hypoxanthine derivative N-alpha-5-(1,6-dihydro-6-oxo-9-purinyl)pentyloxy-carbonyl-L- arginine (ST 789). Experimental immunosuppression was carried out by injecting hybrid B6D2F1 mice with a single dose of cyclophosphamide (100 mg/kg, i.p.) 2 hours prior to treatment with ST 789. In the young, we found that ST 789 markedly restored the splenocyte proliferative response, assessed as total amount of 3H-thymidine incorporated by mitogen-stimulated cells. In the adult, however, the ST 789-induced recovery was less pronounced. Finally, the effects of ST 789 treatment on Con A-induced IL-2 production by splenocytes were studied in normal and immunosuppressed mice of 10 weeks.