IL4 and abortion: Several studies have reported that abortion-prone CBA/J females demonstrate decreased circulating and placental levels of IL-4 and IL-10 (18, 48–52) and that experimental therapeutics at various time points including a B7 monoclonal antibody, adenoviral-mediated heme oxygenase-1 overexpression, progesterone or its derivatives, adoptive transfer of Tregs, or alloimmunization, all decrease abortion rate and this is associated with increased IL-4 and IL-10 and/or Th2/Th1 ratios (18, 48–50, 52–55).