Expectant mothers do not typically reject their babies by mounting an immune response. A systemic change occurs in the immune systems of pregnant women that lessens the possibility of fetal rejection as well as other potentially harmful autoimmune reactions. In the March issue of Nature Immunology, British researchers show that pregnancy induces an immune-tolerant state by increasing the number of particular immune cells known as CD4+CD25+ regulatory T cells.
Regulatory T cells act to control other T cells, thereby preventing attack on tissues that might be perceived as foreign by the immune system. Alexander Betz and colleagues found that pregnant mice had two to three times the number of circulating regulatory T cells of nonpregnant age-matched female mice. These increases occurred soon after conception, but waned after birth. When the regulatory T cells were depleted in the pregnant mice, spontaneous rejection of their fetuses occurred. These results suggest that the regulatory T cells might be the principal means by which pregnant mothers tolerate their developing embryos. This research might lead to diagnostic tests for infertile couples who experience recurrent pregnancy losses.
Alexander G. Betz
MRC Laboratory of Molecular Biology
Tel: +44 1223 402072
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(C) Nature Immunology press release.
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