The basis and value of currently used immunomodulatory therapies in recurrent miscarriage

Recurrent miscarriage (RM) without an obvious identifiable cause may arise from excessive maternal T and natural killer (NK) cell activity against the trophoblast or early embryo. Impaired regulatory T cell function leading to increased pro-inflammatory Th17 and NK cell cytotoxicity may be central. Ongoing subclinical endometrial infection and/or inflammation with increased secretion of TNFα and stimulation of autoimmunity to heat shock proteins may also be contributory. Therapies with a varying theoretical basis and clinical evidence aimed at reducing excessive endometrial immune activity have been used non-selectively in women with RM with variable success. Recent work has now improved our understanding of the role of the different immune cells and proteins that are important at each stage of a normal pregnancy. The vulnerability of the early embryo to T and NK cell-mediated rejection suggests that immune-based therapies need to be maximally effective during early pregnancy. Targeting RM women with demonstrable T and NK cell activity may improve the overall clinical efficacy of these treatments. It may also prevent costly and possibly harmful use in women who are unlikely to respond, and make better use of scarce resources. This report describes the underlying principles behind the use of the different immune-based therapies. The broad evidence supporting their efficacy is also described, as are the possible adverse consequences. Suggestions are also made on how the maternal immune system may be positively modulated using current, widely available treatments that have minimal or no side effects.