A fish cell surface receptor defined by a mAb mediates leukocyte aggregation and deactivation

Cell adhesion molecules play a key role in the inflammatory response. Selec tins, integrins and immunoglobulin gene superfamily adhesion receptors medi ate the different steps of leukocyte migration from the blood-stream toward s inflammatory foci. In addition to their adhesive function, these receptor s modulate major cellular processes such as cell activation, growth, differ entiation and death. To characterise the fish molecules involved in cell ad hesion, a panel of mAbs was raised by immunising mice with macrophages from the marine fish gilthead seabream (Sparus aurata L.). One of these mAbs, w hich we named anti-Aggregatin, was found to induce a rapid heterotypic aggr egation of seabream leukocytes. Anti-Aggregatin defined a 140-kDa cell surf ace receptor which was highly expressed by macrophages and was up-regulated after co-stimulation with LPS and MAF. Functionally, the cell adhesion whi ch occurred upon exposure to anti-Aggregatin required Ca2+, an intact cytos keleton and an active cell metabolism. More importantly, Aggregatin engagem ent resulted in strong inhibition of the phagocyte respiratory burst, altho ugh the cells showed neither loss of viability nor DNA fragmentation. The r esults are discussed in relation to the potential role of cell adhesion mol ecules in fish immune responses. (C) 2001 Published by Elsevier Science Ltd .