A rat monoclonal antibody that binds specifically to mouse T lymphoblasts and inhibits IL 2 receptor functions: a putative anti-IL 2 receptor antibody.

To obtain an anti-interleukin 2 (IL 2) receptor antibody, we immunized rats with phorbol myristate acetate-pulsed mouse T lymphoblasts. The spleen cells of the rats were fused with rat myeloma cells. Several stable clones of hybridoma cells were obtained that produced monoclonal antibodies (mAb) reacting specifically with mouse T lymphoblasts. One of these mAb, AMT-13, showed characteristics of a putative anti-IL 2 receptor antibody. As tested by FACS analysis, the mAb AMT-13 binds to murine T lymphoblasts or to IL 2-dependent T cell lines, but not to B lymphoblasts, thymocytes, splenocytes, lymph node cells, or bone marrow cells. The mAb AMT-13 inhibited in a species-specific and dose-dependent manner: i) the capacity of mouse T lymphoblasts to absorb IL 2 activity, and ii) the capacity of mouse T lymphoblasts to proliferate in response to IL 2. The function of T lymphoblasts of rat origin was not affected by the mAb AMT-13. The time course of the acquisition by mitogen-stimulated spleen cells of the capacity to absorb IL 2 activity was paralleled by that of their capacity to bind the mAb AMT-13. Preliminary biochemical analysis of the antigen recognized by AMT-13 revealed a major component with an apparent m.w. of 50,000 to 60,000. According to these data, the mAb AMT-13 seems to be directed against an antigenic determinant of the murine IL 2 receptor molecule.