Enhanced phagocytosis of immune complexes in pregnancy.

Utilizing an in vitro immunofluorescence phagocytosis assay for the detection of circulating immune complexes sera from pregnant women, from women taking contraceptive agents and age-matched controls were tested for their effect on the phagocytosis of immune complexes by normal peripheral blood polymorphonuclear leucocytes (PMN). Immune complexes present in the serum of a patient with seropositive rheumatoid arthritis and heat-aggregated IgG (COHN fraction II) were used as substrate. A significant enhancement of the phagocytosis of immune complexes by PMN in the presence of increasing amounts of pregnancy serum was seen using rheumatoid arthritis serum as well as heat-aggregated IgG. Serum from patients taking contraceptive drugs and controls showed no effect on the phagocytosis of such complexes in vitro. These observations suggest that pregnancy serum contains factors which enhance the phagocytosis of immune complexes possibly resulting in an increased clearance of such complexes. The commonly seen improvement of rheumatic diseases in the course of pregnancy might at least partially be due to this mechanism.