Male microchimerism and HLA compatibility in French women with sclerodema: a different profile in limited and diffuse subset

Objectives. Male microchimerism (Mc) persisting from pregnancy has been found at greater frequencies and/or higher quantities in women with scleroderma (SSc) compared with controls, suggesting a possible role in disease development. Moreover, women with an HLA-compatible child have a higher risk to develop SSc. We tested the hypothesis, on our French SSc cohort, that women with lcSSc and dcSSc, two distinct clinical subsets, have a different profile in terms of Mc and HLA compatibility in families. Methods. We studied 98 women (52 lcSSc and 46 dcSSc) for male Mc, by real-time PCR, in their whole blood and/or peripheral blood mononuclear cells (PBMC). Similarly, 91 matched healthy women were analysed. Complete HLA-DRB1 typing was obtained for 58 SSc and 68 control families (proband/children). Results. Women with lcSSc (N ¼ 50) had male Mc more often in their whole blood than women with dcSSc (N ¼ 40, 20 vs 5%, P ¼ 0.038), but not significantly more than controls. By contrast, women with dcSSc (N ¼ 36) hold Mc more often in PBMC (25 vs 9%), but not significantly and have greater quantities than controls (N ¼ 82, P ¼ 0.048). This contrast is also visible in feto-maternal HLA-DRB1 compatibility, which was increased only among women with lcSSc (N ¼ 33) compared with controls (N ¼ 68, P ¼ 0.003). Conclusion. For the first time, we showed that women with lcSSc and dcSSc hold male Mc in different blood compartments. Furthermore, a distinct pattern between the two SSc subtypes is observed for feto-maternal HLA-DRB1 compatibility. These results suggest a different mechanism behind each type of disease.