Pregnancy, persistent microchimerism, and autoimmune disease.

Fetal cells have been detected in maternal peripheral blood in the majority of normal pregnancies, and the influx of fetal cells into the maternal circulation increases during parturition. Recently, fetal progenitor cells have been found to persist in maternal peripheral blood for decades after childbirth--which has potential implications for some autoimmune diseases in women, such as scleroderma. Scleroderma has a strong female predominance, a steep increase in incidence in women following the childbearing years, and clinical similarity to the chronic graft-versus-host disease that occurs after allogenic bone marrow transplantation. This article explores the hypothesis that microchimerism (nonhost cells) contributes to the pathogenesis of scleroderma and certain other autoimmune disorders.