Physiological aspects of circulating immune complexes in the normal population

Abstract

Circulating immune complexes (CIC) have been investigated in 100 normal subjects; the RIA-Raji and the C 1 q-BA conventional methods, as well as a new solid phase microassay utilizing purified C I q and the systematic search of cryoprecipitates were employed. CIC serum levels did not differ in regards to sex; in relation to age, values for Clq-BA were identical in subjects from 0 to 60 years and also in those beyond age 60; the differences encountered by RIA-Raji or by the C 1 q-SP microassay in these two main groups were not statistically significant. Cryoprecipitates were present in 100% of tne 68 examined subjects. Immunoglobulins (G, A and M), anti-nucleic acid (DNA and Poly A) and CIC (by the three methods) were present in the cryoprecipitates while lymphocytotoxins, rheumatoid factor and C3 were undetectable; protein content of the cryoprecipitates increased significantly with age, reaching a normal superior limit of 0 52 mg/ml beyond age 30. These findings further support the role played by CIC in normal immune response and may help in the understanding of the physiopathology of clinical conditions associated with immune complexes.