Effects of human C 1 inhibitor on complement-mediated human leukocyte chemotaxis.

Human C1 inhibitor (C1 INH) enhances the chemotactic responsiveness of human leukocytes to lipopolysaccharide (LPS), AgAb complex, and zymosan-activated plasma or serum when added to the compartment of the chemotaxis chamber containing the cells. It seems to affect cells directly and causes an increased number of leukocytes to respond to the chemotactic factors at early time intervals. Spontaneous motility does not appear to be affected. Results of studies employing anti-C3 and anti-C5 sera seem to indicate that the chemotactic factor derived from C5 is involved in the C1 INH induced enhancement of chemotaxis. In fact, preliminary experiments utilizing trypsinactivated C3 as a chemotactic source indicate that C1 INH causes inhibition of chemotactic response to C3a. C1 INH is the first naturally occurring plasma component reported to cause enhanced chemotactic responsiveness.