Culicoides antigen extract stimulates equine blood mononuclear (BMN) cell proliferation and the release of eosinophil adherence-inducing factor(s)

Intradermal injection of a Culicoides antigen extract (CAgX) induces T lymp hocyte and eosinophil accumulation in the skin of horses with sweet itch. B lood mononuclear (BMN) cells from normal ponies proliferate when stimulated by mitogen (phytohaemagglutinin, PHA) or antigen (tetanus toroid, rr) and, as shown here, release soluble factor(s) that induce eosinophil adherence. CAgX also caused concentration dependent proliferation of BMN cells from s weet itch and normal ponies [stimulation index: 29 (13) and 17 (7) for BMN cells from sweet itch and normal ponies, respectively during the active pha se of disease; 4 mug protein ml(-1) CAgX; 168 h]. A heat labile factor(s) w hich caused eosinophil adherence was also released [sweet itch ponies: 6.0 (1.6) per cent adherence versus 1.3 (0.4) per cent; normal ponies: 6.6 (0.5 ) per cent adherence versus 0.9 (0.1) per cent for supernatants from CAgX ( 4 mug protein ml(-1); 48 hours) stimulated versus unstimulated BMN cells, r espectively]. These results suggest that soluble proteins released from T l ymphocytes could affect eosinophil function in the lesional skin of sweet i tch horses. (C) 2001 Harcourt Publishers Ltd.