Peripheral natural killer cytotoxicity and CD56(pos)CD16(pos) cells increase during early pregnancy in women with a history of recurrent spontaneous abortion

For diagnostic purposes we assessed peripheral natural killer (NK) cell cyt otoxicity and NK and T cell numbers to assess their putative predictive val ue in recurrent spontaneous abortion (RSA). A total of 43 women with subseq uent pregnancy, 37 healthy controls and 39 women successfully partaking in an in-vitro fertilization (IVF) procedure, were included in the study. We s how that before pregnancy, levels of NK cytotoxicity and numbers of both si ngle CD56(pos) and double CD56(pos)CD16(pos) cells were similar between RSA women and controls. But notably, within the RSA group, NK cell numbers of <12% were strongly associated with a subsequent pregnancy carried to term. Supplementation of folic acid led to an increase of single CD56(pos) cells, but cytotoxic function appeared unaffected. The expression pattern of kill er inhibitory receptors on CD56(pos) cells was not different between patien ts and controls. A longitudinal study revealed that, compared with controls , in RSA women higher numbers of double CD56(pos)CD16(pos) cells were prese nt during early pregnancy, paralleled by an increase in cytotoxic NK cell r eactivity. The single CD56(pos) population decreased in number. In conclusi on, the analysis of peripheral NK cell characteristics appears a suitable d iagnostic tool in RSA. Immunomodulation aimed at NK cell function appears a promising therapeutic measure.