Inhibition of IL-15–induced proliferation of ATL cell lines by anti–IL-2R α, β, or γ chain antibodies. The percent inhibition was based on a comparison with cells cultured in IL-15 alone. The anti-β and γ chain antibodies significantly inhibited the proliferation induced by IL-15, with the maximum inhibition of anti-β. The anti-α chain antibody did not inhibit the proliferation. The extent of the inhibition was the smallest in the OMT cell line.