Nonparticipation of C1q in the decrease of complement activity in the cold in sera of patients with chronic liver diseases.

Serum and plasma samples taken simultaneously from 560 patients with various diseases were examined for hemolytic complement activity (CH50) after incubation at 4 degrees C for 20 h. Serum CH50 titers less than 20 U/ml were observed in 39 cases and among them, a difference between serum and plasma CH50 of more than 5 U/ml were observed in 16 cases. Diagnosis of most of them were chronic liver diseases. To analyze the dissociation of CH50 titers between serum and plasma, sequential estimations of CH50 were performed on serum and plasma samples which showed the dissocation incubated at 4 and 37 degrees C. Marked decrease in CH50 titers was obtained in sera but not in plasma incubated at 4 degrees C. In such sera, however, no significant decrease of protein amount and agglutinating activity of C1q was observed. The result could indicate that C1q would not participate in the decrease of serum hemolytic activity in the cold, suggesting an activation of complement other than the classical pathway.