740 Effect of Anti - Il - 2 on Immune Responses

A large body of exper imental data indicates that T cell growth factor, interleukin 2 (IL-2), j participates in a n u m b er o f in vitro assays for immune responses. For example, IL-2 has been shown to maintain the in vitro proliferat ion of antigen-specific, cytolytic, and helper T cell lines (1, 2); to contr ibute to the format ion of cytotoxic T lymphocytes in cultures stimulated with alloantigen (3); to enhance thymocyte mitogenesis, and to mediate the development of erythrocyte-specific ant ibody-producing cells in T cel l-deficient cultures (4-6). Based on these activities in vitro it seems likely that IL-2 will also play a role in cellmediated immunity in vivo. Tests for the in vivo relevance o f IL-2 would be greatly facilitated by the deve lopment of specific reagents that could detect the molecule independent of its biological activity, or block its action, or both. Specific antibodies to IL-2 might be expected to have such properties; in addition, they could be valuable specific immunoadsorbents in IL-2 purification and characterization, and in studies of IL-2 biosynthesis. With this in mind, we have raised ant ibody in rabbits using as antigen a highly purif ied fraction of mouse IL-2 whose isolation f rom spleen cell cultures we have recently described (7). T h e characterization of these anti-IL-2 antibodies, and some of their effects in vitro and in vivo, are repor ted here.