Increased microchimerism in peripheral blood of women with systemic lupus erythematosus: relation with pregnancy

Objective We aimed to determine the presence, amount and origin of microchimerism in peripheral blood of pregnant and non-pregnant parous women with systemic lupus erythematosus (SLE) as compared to control subjects.Methods We performed a comparative study in which peripheral blood was drawn from eleven female non-pregnant SLE-patients and 22 control subjects, and from six pregnant SLE-patients and eleven control subjects during gestation and up to six months postpartum. Quantitative PCR for insertion-deletion polymorphisms and null alleles was used to detect microchimerism in peripheral blood mononuclear cells and granulocytes.Results Microchimerism was detected more often in non-pregnant SLE-patients than control subjects (54.4% vs. 13.6%, respectively; p=0.03). When present, the median total number of foetal chimeric cells was 5 gEq/106 in patients and 2.5gEq/106 in control subjects (p=0.048). Microchimerism was mostly foetal in origin; maternal microchimerism was detected in one patient and one control subject. In control subjects, microchimerism was always derived from only one source whereas in 50% of patients it originated from multiple sources. The pregnant patients had a significantly higher median number of foetal chimeric cells in the granulocyte fraction just after delivery than control subjects (7.5 gEq/106 vs. 0 gEq/106, respectively; p=0.02).Conclusion Just after delivery, SLE-patients had more microchimerism than control subjects. Three months post-partum, microchimerism was no longer detectable, only to reappear many years after the last pregnancy, more often and at higher levels in SLE-patients than in control subjects. This suggests that these chimeric cells may originate from non-circulating foetal chimeric stem cells.

Automated summary

This study aimed to investigate the presence, amount, and origin of microchimerism in peripheral blood of pregnant and non-pregnant women with SLE. The results showed that microchimerism was more common in non-pregnant SLE patients compared to control subjects. The majority of microchimerism originated from the fetus. Pregnant SLE patients had significantly higher levels of fetal chimeric cells in their peripheral blood after delivery.