Low molecular weight C1q-precipitins in hypocomplementemic vasculitis-urticaria syndrome: partial purification and characterization as immunoglobulin.
A lupus-like syndrome involving chronic urticaria with cutaneous vasculitis, systemic symptoms, hypocomplementemia with preferential depletion of C1q, and low m.w. (7S) C1q-precipitins has recently been defined. The C1q-precipitin activity (C1q-p) seems to represent a diagnostic marker of the disease, but its chemical nature is not yet clear. We have partially purified and characterized C1q-p from the serum of two patients with this syndrome and compared its activity with the C1q-precipitating activity of aggregated human gamma-globulin (AHGG) anti-C1q antibodies, and several polynucleotides including DNA and polyinosinic acid. C1q-p was found to partition with IgG during precipitation by ammonium sulfate and low ionic strength buffer as well as during column chromatography on DEAE-cellulose and G-200 Sephadex. Like AHGG, but in complete contrast to the polynucleotides, the C1q-precipitating activity of C1q-p was sensitive to pepsin, trypsin, and acidic conditions, but unaffected by DNAse or RNAse; the C1q-precipitating activity of anti-C1q antibody was not diminished by any of these procedures. Thus, C1q-p consists of gamma-migrating protein of low m.w., and its C1q-precipitating activity is indistinguishable from that of AHGG. These results are consistent with the concept that C1q-p is comprised, at least in part, of IgG that binds C1q via the Fc portion of the molecule.
D001667:Binding, Competitive; D002908:Chronic Disease; D003172:Complement C1 / Q000172:deficiency*; D004587:Electrophoresis, Agar Gel; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008875:Middle Aged; D008970:Molecular Weight; D011119:Polynucleotides; D011234:Precipitins / Q000302:isolation & purification; D013577:Syndrome; D014581:Urticaria / Q000150:complications*; D018366:Vasculitis, Leukocytoclastic, Cutaneous
D003172:Complement C1; D011119:Polynucleotides; D011234:Precipitins