SECA, a new mediator of the human eosinophil response.

Spontaneous eosinophilic chemotactic activity (SECA) present in human sera can mediate the directed movement of normal human eosinophils. Our data utilize normal peripheral blood eosinophils obtained from subjects with 500 eosinophils/m3 or less. SECA is defined as that chemotactic activity for eosinophils present in serum that has been heat-inactivated immediately after collection. It was demonstrated in patients with severe chronic eczema with eosinophilia (20 to 30%); mixed collagen vascular disease with vasculitis; clinical serum sickness; acute glomerulonephritis, and chronic membranoproliferative glomerulonephritis. Control sera were obtained from normal, healthy individuals. The data indicated: (1) that SECA in patient sera was significantly higher than in control sera; (2) when activated by endotoxin, no additional chemotactic activity was generated from patient sera over that spontaneously present--by contrast, addition of endotoxin to control sera did result in increased chemotactic activity; (3) sera from patients with extrinsic bronchial asthma had no SECA.