PHA INDUCES IL-2 RECEPTORS ON B-CLL CELLS AND IS A POTENTIAL BIOLOGICAL RESPONSE MODIFIER FOR THE LIL-2-DIPHTHERIA TOXIN, DAB(486)IL-2

DAB(486)IL-2 is an IL-2-diphtheria toxin conjugate which was developed to be specifically cytotoxic to cells bearing high affinity IL-2 rece ptors. The high affinity IL-2 receptor is a heterodimer comprising p55 and p75 subunits. While the p75 subunit appears to be ubiquitously ex pressed among the common North American leukemias and lymphomas, the p 55 subunit is more restricted in its expression. To broaden the therap eutic relevance of the DAB(486)IL-2 we have sought physiologically fea sible inducers of the p55 IL-2 receptor subunit. This report describes that PHA, in vitro, induces the p55 IL-2 receptor subunit on initiall y p55-negative B-CLL cells and converts toxin-insensitive leukemia cel ls to a toxin-sensitive state.