Circulating immune complexes, free antigen and alpha 1-antitrypsin in levels in sarcoidosis patients.

Consecutive serum samples from 26 sarcoidosis patients were examined for circulating immune complex (IC) activity. Fifteen (58%) gave IC-positive reactions in a complement consumption (CC) test and a significant difference as regards anticomplementary was observed when comparing patients in clinical stages 2 and 1 respectively (P less than 0.01) The serum alpha 1-antitrypsin levels were not correlated (r=0.36) to the results of the CC-assay. The duration of IC-occurrence was studied, by two IC-assays, over 1 1/2 to 2 years. The majority of the positive reactions were registered in patients in clinical stage 2. Isolated IC was used for immunization of rabbits. Absorbed immune sera produced a single precipitate of postalbumin mobility with seven out of 36 sarcoidosis sera. In two cases a tailing of the recipitate suggested that the antigen was in complex formation. Immunoelectrophoresis indicated identity between the antigen detected in different sarcoidosis sera. No precipitates were observed using 130 sera from other patients, and screening of 100 blood donors revealed one positive reaction. The antigen, which eluted in the first protein peak on Sephadex G-200, has not been identified serologically.