Monoclonal antibody which has the neutralizing activities for human IL-2

Six monoclonal antibodies against recombinant human interleukin-2 (IL-2) were successfully prepared by fusing NS-1 with spleen cells of BALB/c mice immunized with human recombinant IL-2. The specificities of these monoclonal antibodies were confirmed. By enzyme linked immunosorbent assay (ELISA) method, the antibody concentrations of each ascitic fluid obtained from BALB/c-nu/nu transplanted with the established hybridoma clones were varied for 10(3) to 10(5) depending on the clone. By SDS-PAGE analysis with immunoprecipitates formed between monoclonal antibodies and recombinant human IL-2, all monoclonal antibodies reacted unequivocally with recombinant human IL-2. Two monoclonal antibodies (designated as KNT-1 and KNT-2) out of six established clones reacted with natural human IL-2 molecule obtained from cultured human peripheral blood lymphocytes (PBL) stimulated with PHA-P and TPA. KNT-1 and KNT-2 monoclonal antibodies have inhibitory effects on the proliferative response of natural killer (NK-7) cell (one of the IL-2 dependent cultured cell lines) elicited by recombinant, natural human, or natural rat IL-2. Monoclonal antibody, KNT-1, inhibited activities of both recombinant or natural human IL-2, but did not neutralize activities of IL-2, derived either from murine EL-4 or from rat spleen cells. Another monoclonal antibody, KNT-2, had neutralizing activity for either recombinant or natural human IL-2 and eliminated the activity of rat-derived IL-2, but did not interfere with the activity of murine IL-2. The remaining four monoclonal antibodies (designated as KNT-3, -4, -5 and -6) did not affect the proliferative response of NK-7 cells elicited by natural human, rat and murine IL-2. These observations indicate that functional portion(s) of IL-2 molecules from different species have somewhat different structures.