Isolation and characterization of a C4-like complement protein from chicken plasma

The motivation for this study was to find a third genetic marker of the chicken B complex. The approach followed three stages: First, isolate and purify the fourth component of complement (C4) from chicken plasma. Secondly, generate a monospecific antibody to C4 to permit a study of its genetic variation. Thirdly, investigate the linkage relationship between C4 and B complex.;The primary objective achieved was that a C4 like protein was isolated and purified using affinity chromatography. The purified C4 protein has a molecular weight of 210,000 daltons determined by SDS-PAGE and dissociates into three subunits of 91,000, 79,000 and 30,000 daltons after reduction.;The monospecific antisera to chicken C4 was generated from rabbits. This antiserum not only cross-reacted with human C4 but also blocked the hemolytic ability of both human and chicken plasma.;A kinetic study of C4 protein serum concentration was carried out. The means levels of C4 protein were 1.06 mg/ml, 1.30 mg/ml, 1.90 mg/ml, 2.20 mg/ml, and 2.50 mg/ml at age of 2 weeks, 4 weeks, 6 weeks, 10 weeks and 20 weeks, respectively.;The C4 protein level differed significantly between tumor progressors and tumor regressors and tumor regressors after Rous sarcoma virus inoculation. The progressors had an average C4 protein level of 77.3 d(\u272), which is less than that of the regressors, 85.7 d(\u272).;A Class I antigen was immunoprecipitated from erythrocytes by monospecific anti-C4 antiserum whereas a Class II antigen (in question) was immunoprecipitated from B lymphocytes by the same antiserum.;The molecular weight of chicken C4, its hemolytic function in tumor regression and its relationship to Class I antigens have been found to be rather similar to the C4 properties of the human and mouse systems. Thus, it seems that chicken C4 is linked to the MHC just as found in human and mouse system. In particular, this possibility was strongly suggested by the results of the elaborate immunoprecipitation study. However, conclusive evidence for the linkage relation between C4 and B complex requires further study