The detection of circulating immune complexes and IgG and IgM rheumatoid factors in normal human pregnancy

The development of immune complexes (IC) and rheumatoid factors (RF) during normal, uncomplicated pregnancy is a controversial issue. Discrepancies in previous reports are due most likely to the different methods used to detect both IC and RF. Using four sensitive radioimmunoassays for immune complexes employing both Clq and mRF and employing sensitive and specific radioimmunoassays for the detection of IgM-RF and IgG-RF, we examined the sera of 35 normal subjects in their third trimester of pregnancy. Immune complex concentrations as measured by four assays were not increased during gestation. However, both IgM-RF and IgG-RF were significantly elevated even though the concentrations of immunoglobulins M and G were virtually identical to the controls. These observations provide further insight into the immunological changes associated with pregnancy. (Am J Reprod Immunol. 2:208-211.)