SECRETION OF IL-16 (LYMPHOCYTE CHEMOATTRACTANT FACTOR) FROM SEROTONIN-STIMULATED CD8(-CELLS IN-VITRO() T)

At sites of inflammation, mononuclear cells are in close contact with aggregated platelets, Although the physiologic role of this associatio n is not clear, this proximity suggests that platelet-derived mediator s may play a role in chemoattraction of T lymphocytes, In the current study we investigated serotonin receptor-bearing lymphocyte modulation of T cell migration, Serotonin-stimulated human blood mononuclear cel ls secrete lymphocyte chemoattractant activity with selective activity for CD4(+) T cells, This chemoattractant activity was observed within 2 h of exposure to serotonin and was blocked by serotonin type 2 rece ptor antagonists, Molecular sieve chromatography of supernatant from s erotonin-stimulated PBMCs revealed a single peak of T cell chemoattrac tant activity with an apparent molecular mass of 56 kDa and a pi of 9. 1. Neutralizing experiments with specific mAbs indicated that the sero tonin-induced chemotactic factor was the previously characterized lymp hocyte chemoattractant factor (LCF), recently designated IL-16. Seroto nin induced secretion of IL-16 from CD8(+), not CD4(+), T cells which did not require de novo protein synthesis, These studies suggest that serotonin, via serotonin type 2 receptors, may promote the recruitment of CD4(+) T lymphocytes into an inflammatory focus.