Correlations of Y chromosome microchimerism with disease activity in patients with SLE: analysis of preliminary data

BACKGROUND: Recently it has been suggested that microchimerism may have a significant role in the aetiopathogenesis of some autoimmune diseases. OBJECTIVES: To evaluate the incidence of microchimerism in systemic lupus erythematosus (SLE), to quantify the phenomenon, to evaluate changes of microchimerism during follow up, and to correlate these data with clinical and laboratory variables. METHODS: Patients were selected for the study on the basis of the following criteria: (a) pregnancy with at least one male offspring; (b) no history of abortion and blood transfusion. Microchimerism was detected using a competitive nested polymerase chain reaction for a specific Y chromosome sequence and an internal competitor designed ad hoc. Disease activity and organ involvement were also evaluated. RESULTS: Sixty samples from 22 patients with SLE and 24 healthy controls were examined. Microchimerism was seen in 11 (50%) patients and 12 (50%) controls. The mean number of male equivalent cells was 2.4 cells/100 000 (range 0.1-17) in patients with SLE and 2.5 (range 0.2-1.8) in healthy controls. No differences in the incidence of microchimerism or in the number of microchimeric cells were found between patients and healthy controls. Patients with a history of lupus nephritis had a higher mean number of fetal cells than patients with no such history. Disease activity did not appear to correlate with microchimerism. CONCLUSIONS: The preliminary data suggest that microchimerism does not interfere with the disease course of SLE, although further analysis on larger groups will be necessary to confirm these observations.