Inhibition of pregnancy viability in mice following IL-2 administration.

The influence of administration of interleukin-2 (IL-2) on syngeneic and allogeneic murine pregnancy has been investigated. Human or mouse recombinant IL-2 (rhIL-2 and rmIL-2), or partially purified rat IL-2, was inoculated i.p. into C57B1 mice following syngeneic mating but before embryo implantation. This inhibited subsequent fetal development in up to 100% of cases, compared with mice inoculated with control material, including recombinant human interleukin-1 alpha (IL-1 alpha), where no inhibition of pregnancy viability was observed. Similar data were obtained in both syngeneic and allogeneic matings when rhIL-2 was administered on Day 1 of pregnancy. Administration of rhIL-2 during the second pregnancy, rather than a first pregnancy, was less effective. Administration of rhIL-2 during the first pregnancy does not induce a permanent sterility. Histological examination of the endometrium further demonstrated that mice injected with rhIL-2 on Day 1 of their first pregnancy showed a complete absence of embryonic tissue.