Polymorphonuclear leukocyte chemotaxis in systemic lupus erythematosus.

Studies completed thus far indicate that normal human serum contains a specific anionic polypeptide (cochemotaxin) that permits low concentrations of C5a desarg to exhibit chemotactic activity for human polymorphonuclear leukocytes. Under conditions of limited complement activation in vivo, the cochemotaxin may play an important physiologic role by amplifying the chemotactic activity of C5a desarg. The "complex" of C5a desarg plus cochemotaxin probably accounts for most of the chemotactic activity that is generated in human serum after complement activation and also appears to be the target of the heat stable cationic protein inhibitor (Bb fragment of Factor B) that is present in serum from some patients with active systemic lupus erythematosus.