Immune complexes in epidemic (type A) hepatitis. Detection by three methods using laser nephelometry.

Thirty-eight children with acute epidemic hepatitis (Type A) and 22 children in "contact" with the disease, 5 of whom subsequently developed hepatitis, were studied. Three technics based on laser ray nephelometry were employed to investigate the presence of circulating immune complexes. Our results indicated that circulating immune complexes are present in the serum during the course of epidemic hepatitis. These were demonstrated in 79% of the patients. The capacity to fix complement diminishes as the disease evolves toward the convalescent phase. We also detected a similar percentage of immune complexes (80%) in the patients during the incubation period. In the subjects in "contact" with the disease who subsequently did not develop hepatitis, the immune complexes were shown to have a greater capacity to fix complement, and the percentage of immune complexes present was higher (94%). The specificity of the immune complexes was verified by correlating the antivirus A antibody activity with the percentage of C4 in the precipitates obtained by polyethylene glycol (3.5%).