Microchimerism of maternal origin persists into adult life

Abstract

Recent studies indicate that fetal cells persist in maternal blood for decades after pregnancy. Maternal cells are known to engraft and persist in infants with immunodeficiency, but whether maternal cells persist long-term in immunocompetent offspring has not specifically been investigated. We developed sensitive human leukocyte antigen-specific (HLA-specific) PCR assays and targeted nonshared maternal HLA genes to test for persistent maternal microchimerism in subjects with scleroderma and in healthy normal subjects. Nonshared maternal-specific DNA was found in 6 of 9 scleroderma patients. In situ hybridization with double labeling for X and Y chromosome-specific sequences revealed female cells in peripheral blood samples from 2 male scleroderma patients. HLA-specific PCR also frequently revealed persistent maternal microchimerism in healthy control subjects. The mean age of all subjects with maternal microchimerism was 28 years (range: 9-49 years). With few exceptions, mothers of subjects with persistent maternal microchimerism were HLA incompatible with subjects for class I and class II alleles. These results clearly indicate that HLA-disparate maternal cells can persist in immunocompetent offspring well into adult life. The biological significance of maternal microchimerism and whether it might contribute to autoimmune disease requires further investigation.

Figure 1

HLA-B44–specific PCR of DNA extracted from PBMCs of a 49-year-old scleroderma patient who was B44-negative and whose mother was B44-positive. Lanes 3 and 5 are patient samples from 2 different draw dates. Lane 7 is a positive control from the mother, and lane 8 is a positive control from a homozygous cell line. The patient’s HLA-B alleles were B*0801 and B*3508, and lanes 10 and 11 are negative controls derived from homozygous cell lines with these alleles. Lane 12 is a negative reagent control, and lanes 2, 4, 6, and 9 are blank.

Figure 2

HLA-DRB5*01-specific PCR of DNA extracted from PBMCs of a scleroderma patient and a normal subject. The DRB5 gene is present only on some HLA haplotypes. Both mothers had DRB5*01 and both subjects did not. Lanes 3 and 4 are patient samples (different aliquots from the same draw date). Negative controls from homozygous cell lines with alleles similar to the patient’s are shown in lanes 5 and 6, and a positive homozygous control is shown in lane 7. Lanes 8–11 are 2 draw dates from a normal subject. Lanes 12 and 13 are negative cell line controls, and lane 14 is a positive homozygous cell line control. Lane 2 is blank. There was no alternative source of DRB5*01 DNA in the normal subject. The scleroderma patient also had children with DRB5*01 (see text).

Figure 3

In situ hybridization with double labeling for X and Y chromosome–specific sequences of PBMCs from male patients with scleroderma (above) and scleroderma/myositis overlap (below). A cell with 2 X chromosomes (green) is seen among male cells that contain both a Y chromosome (red) and an X chromosome (green) in each of the patients. (In the top panel, the X and Y signals are superimposed in the cell adjacent to the cell with 2 X signals.) The only known sources of female cells in the patients were their mothers. Neither patient had a history of blood transfusion or was a twin. ×100.