Antibodies to phosphatidylethanolamine and phosphatidylserine are associated with increased natural killer cell activity in non-male factor infertility patients

Antiphospholipid antibodies (APA) have been identified in patients with rec urrent pregnancy loss and IVF failure, Of these, antiphosphatidylethanolami ne (aPE) and antiphosphatidylserine (aPS) may have special significance. A link between increased natural killer cell activity (NKa+) and trophoblast cell apoptosis has also been reported, This study was undertaken to determi ne how the APA profile was associated with peripheral NK cell activity. We evaluated 197 female IVF candidates for APA and NKa, Eighty-nine patients ( 45%) were APA+ and of these, 51 (57%) were aPE/aPS+. Fifty-four patients (2 7%) had increased NK cell activity. Some 51% of APA+ and 78% of aPE/aPS+ pa tients had increased NK cell activity compared with 8% and 13% when APA and aPE/aPS tested negative respectively (P < 0.0001). Non-male factor inferti lity patients were APA+ and NKa+ in 57% and 34% of cases respectively, comp ared with 19% and 13% if a pure male factor was present. Some 88% of aPE/aP S+, non-male factor patients had increased NK cell activity, compared with 12% who tested aPE/aPS negative (P < 0.0001) and 25% of aPE/aPS+, isolated male factor patients (P < 0.0001). These findings establish a direct relati onship between APA (specifically aPE/aPS) and increased peripheral NK cell activity among non-male factor infertility patients. It is possible that AP A do not directly cause reproductive failure but rather function as markers or intermediaries for an underlying, abnormal activation of cellular immun ity.