High-affinity receptors for vasoactive intestinal peptide on human myeloma cells

Cultured human myeloma cells of the U266 line and leukemic T cells of the Jurkat line bound synthetic [125I]Tyr10-vasoactive intestinal peptide1-28 ([125I]VIP1-28) specifically and with an affinity similar to that of neuroendocrine cells. Specific binding reached equilibrium after 2 h at 22 degrees C for both myeloma cells and T cells, attained a maximum of 57 to 71% of total binding, and was reversed in 1.5 to 3 h by an excess of non-radioactive VIP1-28. Analyses of the ligand concentration-dependence of binding of the ligand concentration-dependence of binding of [125I]VIP1-28 revealed a mean Kd of 7.6 nM for a mean of 41,207 receptors per myeloma cell and 5.2 nM for 12,266 receptors per T cell. The relative affinity of binding of mast cell-derived VIP10-28 free acid and synthetic analogues suggested differences in specificity between lymphocyte and neuroendocrine receptors. Distinct sets of receptors thus appear to mediate the effects of VIP on functions of both antibody-producing cells and T cells.