Depression of lymphocyte traffic in sheep by vasoactive intestinal peptide (VIP)

Vasoactive intestinal peptide (VIP) is a 28 amino acid-residue neurovascular and gut peptide with a number of important biological activities. Recent in vitro studies suggest an immunomodulatory (depressant) role for VIP. In the present in vivo studies, employing the Hall and Morris sheep lymphocyte traffic model, acute infusions of VIP into cannulated afferent lymphatics of popliteal lymph nodes produced prompt and marked depressions in the output of both small recirculating and blast lymphocytes into popliteal efferent lymph, with a selective effect on T4 (CD4) lymphocytes. It has been suggested that the HIV (AIDS) virus may employ VIP or VIP-like receptors on brain cells and lymphocytes for intracellular access.