Human interleukin-2 anti-idiotypes.

We describe the generation of a monoclonal anti-idiotypic (anti-id) antibody directed against affinity purified rabbit antibodies (id) to recombinant human IL-2. This monoclonal antibody, 6A12, has the ability to inhibit the neutralization of IL-2 activity by the id, suggesting that it may bind at or near the IL-2 neutralizing site on the id. 6A12 exhibits IL-2 agonist activity on PHA-activated human T cells. The purified IgG of 6A12 is also shown to bind to a purified soluble recombinant p55 subunit of the IL-2 receptor. Furthermore, purified 6A12 shows inhibition of IL-2 activity in an IL-2 dependent mouse T cell line (CTLL) and this inhibition can be reversed by excess IL-2. These results suggest that although 6A12 may not be an exact 'internal image' of the receptor binding site of IL-2, it may bind to at least the P55 subunit of the ligand binding site on the high affinity IL-2 receptor complex.