CIRCULATING ANTIGENS AND IMMUNE-COMPLEXES IN SCHISTOSOMA-MANSONI-INFECTED RATS - CHARACTERIZATION BY RADIOIMMUNOPRECIPITATION-PEG ASSAY (RIPEGA)

Abstract

Circulating schistosome antigens (CSA) and circulating immune complexes (CIC) were investigated in rats infected with S. mansoni. The radioimmunoprecipitation-polyethylene glycol (PEG) assay (RIPEGA), with 125I-labeled anti-S. mansoni anti-serum, detected CSA during 2 distinct periods of the infection; the first between the 11th-14th wk of infection and the 2nd between the 11th-14th week after infection. The CH50 [50% hemolytic complement] deviation test revealed the presence of CIC in sera from infected rats, approximately at the 2 periods when CSA were detected. At 6 wk of infection, the levels of CIC in infected rats were not different from those in control rats. A more sensitive method characterized Ig[immunoglobulin]G2a in C1q[q fragment of 1st component of complement]-binding CIC from infected rats. The use of RIPEGA on material eluted from infected rat serum after passage through an anti-IgE immunosorbent showed the presence of schistosome antigen at week 4, and at higher levels at week 6. CH50 levels in infected rat serum were lowered between the 2nd-4th wk, the 5th and the 8th wk and after the 12th wk of infection. The possible role played by CIC in the protective mechanisms to a S. mansoni challenge infection in rats is discussed.