TNF and infection: On the other hand, P4 is able to inhibit the secretion and toxic effects of infection-induced TNF-α in both fetal mononuclear cells isolated from umbilical cord blood and peripheral blood mononuclear cells (PBMCs) from women with unexplained recurrent miscarriage [27], as well as in human monocytes stimulated with heat-killed Escherichia coli or Ureaplasma urealyticum [32], and in human fetal membranes that are also sensitive to the immunomodulatory effects of P4 [25, 26].