High affinity specific binding of vasoactive intestinal peptide to human circulating T cells, B cells and large...

We studied the specific binding of vasoactive intestinal peptide (VIP) to circulating lymphocytes (PBL) of normal subjects using the interaction of 125I-VIP with different PBL fractions and flow cytometry to detect the binding of VIP-coated polystyrene spheres to individual cells of the fractions. Enhanced binding of 125I-VIP was found with T-enriched compared to unseparated or T-depleted PBL preparations. Both CD4 and CD8 T cell-enriched suspensions showed high binding capacity, but the affinity of CD4-enriched preparation for VIP was higher. VIP-coated spheres also bound to individual T cells of PBL, but only a minority of CD4 T cells (32%) and CD8 T cells (23%) bound the spheres. 125I-VIP also specifically bound to fractions enriched for large granular lymphocytes (LGL) and B cells. A consistent proportion of CD16 marker-positive LGL bound VIP-coated spheres (24%, and approximately 15% of B cells also showed this ability. Thus there is marked heterogeneity in the ability of different phenotypes of normal human circulating lymphocytes to recognize this neuropeptide.