Studies of C1 subcomponents in chronic urticaria and angioedema.

C1q, C1r, C1s, C3, C4 and C-1 IA were determined by electroimmunoassay in sera from 150 patients with chronic urticaria or angioedema. Abnormal C1q and C1s levels were found in about 30% of the patients. In seven sera C1r was not measurable due to the appearance of diffuse precipitates. The levels of C3 and/or C4 were decreased in five sera with aberrations of C1 subcomponents in the electroimmunoassay. None of the patients showed reduced C-1 IA levels in the electroimmunoassay. The presence in sera of abnormal C1 subcomponent complexes was studied by crossed immunoelectrophoresis. Sera from 11% of the patients contained C1r-C1s complexes. Increased amounts of alpha2 complexes (C-1r-C-1-S-C-1 IA) were found in 33% of the patients. A major part of the C1q in sera yielding abnormal C1r precipitates had the same electrophoretic mobility as isolated C1q and was not associated with the C1qrs complex. C1 activity in hemolytic tests was low in these sera as well as in sera with decreased C1q levels. In the esterolytic assay for C-1 IA low values were found in 14 patients. Repeated sampling and family studies in appropriate cases gave no evidence for genetically determined deficiencies of C1q, C1r or C-1 IA.