Monocyte 5-HT1A receptors mediate pindobind suppression of natural killer cell activity: modulation by catalase

Serotonin (5-hydroxytryptamine; 5-HT) modulates constituents of the immune system. 5-HT1A receptor antagonists potently suppress lymphocyte function. NK cell activity (NKCA) was measured after exposure of mononuclear cells to the 5-HT1A receptor antagonist pindobind and the 5-HT1C/2 receptor antagon ist ketanserin. Elutriated monocytes were exposed to pindobind, incubated w ith peripheral blood lymphocytes (PBL) in the presence or absence of an H2O 2 scavenger catalase, and NKCA measured. Pindobind, but not ketanserin, sup pressed NKCA in vitro. Pindobind-treated monocytes suppressed NKCA, whereas pindobind treatment of PBL did not affect NKCA. Catalase inhibited pindobi nd-induced suppression of NKCA. These data are consistent with previous res ults that 5-HT modulates NKCA via 5-HT1A receptors on monocytes and suggest that 5-HT may abrogate monocyte suppression of NKCA by inhibiting monocyte signals such as H2O2. (C) 2001 Elsevier Science B.V. All rights reserved.