Pregnancy-induced expansion of regulatory T-lymphocytes may mediate protection to multiple sclerosis activity

Pregnancy represents a physiological transitory state of immune tolerance to avoid the rejection of the foetus, and concomitantly of stabilisation of many autoimmune diseases, such as multiple sclerosis (MS). Alterations in regulatory T-lymphocytes (TReg) are known to be involved in organ-specific autoimmune disease pathophysiology. Our goal was to quantify CD4+CD25+ and CD4+CD25hi+ TReg and activated (CD4+HLA-DR+CD38+) T-lymphocytes during pregnancy and puerperium in 13 MS patients in comparison with healthy pregnant and non-pregnant women. During pregnancy, a progressive parallel increase in CD4+CD25+ T-lymphocytes in healthy pregnants as well as MS pregnant patients was observed. The proportion of TReg was significantly higher in all pregnants than in non-pregnant women (p = 0.01), whereas no differences were observed neither in the percentages of total nor activated CD4+ T-lymphocytes. In MS patients, CD4+CD25+ T-lymphocytes significantly decreased when comparing the third trimester with the puerperal period proportions (p = 0.01), whereas CD4+CD25hi+ T-lymphocytes significantly increased (p = 0.002). Our findings are consistent with the expansion of circulating regulatory CD4+CD25+ T-lymphocytes pool with suppressive activity during normal pregnancy and in MS. A different pattern of CD4+CD25hi+ T-lymphocytes between healthy pregnants and MS women, which may represent relevant factors in the activity course of MS.