PHA induces IL-2 receptors on B-CLL cells and is a potential biological response modifier for the LIL-2-diphtheria toxin, DAB486IL-2.

DAB486IL-2 is an IL-2-diphtheria toxin conjugate which was developed to be specifically cytotoxic to cells bearing high affinity IL-2 receptors. The high affinity IL-2 receptor is a heterodimer comprising p55 and p75 subunits. While the p75 subunit appears to be ubiquitously expressed among the common North American leukemias and lymphomas, the p55 subunit is more restricted in its expression. To broaden the therapeutic relevance of the DAB486IL-2 we have sought physiologically feasible inducers of the p55 IL-2 receptor subunit. This report describes that PHA, in vitro, induces the p55 IL-2 receptor subunit on initially p55-negative B-CLL cells and converts toxin-insensitive leukemia cells to a toxin-sensitive state.