FORMATION OF C3a AND C5a ANAPHYLATOXINS IN WHOLE HUMAN SERUM AFTER INHIBITION OF THE ANAPHYLATOXIN INACTIVATOR

Abstract

Two biologically and chemically distinct anaphylatoxins (ATs) could be generated in whole human serum after removal of the AT inactivator (AI) by immune-absorption or after inhibition of AI with 1 M epsilon-aminocaproic acid (EACA). Both human ATs could be generated by treatment of serum with antigen-antibody complexes, which activate the classical complement pathway, and with inulin or yeast, both of which trigger the alternate pathway. The ATs were isolated from serum in active form and characterized as C3a and C5a. Although human C3a had been characterized previously, C5a had not. The molecular weight of human C5a AT was 17,500; its electrophoretic mobility at pH 8.5 was –1.7 x 10–5 cm2 V–1 s–1. The minimal effective concentration in vitro was 7.5 x 10–10 M. The minimal effective doses of human C5a in producing a wheal and erythema in the human skin was 1 x 10–15 mol. The results strongly suggest a biological function for both ATs and indicate that the expression of their activity is controlled by the AI of normal blood plasma.

Complement C3a and C5a Induce Different Signal Transduction Cascades in Endothelial Cells

“…It is possible that endothelial cell retraction caused by the stimulation of endothelial cells with C5a played a role in this process, while stimulation with C3a did not allow leukocyte penetration. Both C3a and C5a are known to increase vascular permeability, and although this may in part be an indirect effect following mast cell degranulation (7,8,49), our data suggest that endothelial cell retraction may also contribute to this phenomenon.…”

“…C3a and C5a are known for their stimulatory effect on leukocytes including chemotaxis of neutrophils, eosinophils, and monocytes (1)(2)(3)(4)(5). Furthermore, the anaphylatoxins can also induce smooth muscle contraction (6) and can evoke an increase in vascular permeability (7,8).…”

Serum Inhibitor of C5 Fragment-Mediated Polymorphonuclear Leukocyte Chemotaxis Associated with Chronic Hemodialysis

“…Furthermore, serum CIA may result from the HD procedure itself. (17). This preparation was subsequently passed though a PM30 membrane (Amicon Corp, Lexington, Mass.…”

Demonstration of Human Leukocyte Degranulation Induced by Sera from Homozygotes and Heterozygotes for Cystic Fibrosis

“…Sera from normal healthy subjects previously inactive by bioassay for ciliary dyskinesia factor (CDF) could be converted to a CDF-positive activity by incubation with EACA. EACA is a known inhibitor of the carboxypeptidase B-like anaphylatoxin inactivator (16), and incubation with EACA is the method of choice for accumulating anaphylatoxins in normal blood (19). Incubation of EACA-treated normal sera and fresh CDF-positive C F sera with carboxypeptidase B produced reversion in all instances to a CDF-negative state, as assessed by rabbit tracheal bioassay (9).…”

“…However, it is not difficult to speculate that C3a may also contribute to the degranulation observed and this possibility has not been excluded completely by Goldstein and his associates (14, 15). Treatment of serum with EACA alone will generate C3a (19) and C3a has been demonstrated to participate in mast cell degranulation (6).…”