Fig. 3

The immune system during pregnancy and after delivery. The T helper 1-type reaction is downregulated during pregnancy. Moreover, immunoregulatory molecules, including progesterone-induced blocking factor (PIBF), placental suppressor factor and trophoblast cell-derived factor, suppress lymphocyte proliferation during pregnancy. After pregnancy, the T helper 2 dominance disappears. In addition, some or all of these immunoregulatory molecules are reduced and lymphocytes can proliferate after delivery