Problem: Decidual natural killer (NK) cells express inhibitory receptors (killer immunoglobulin-like receptors, KIRs), which bind to ligands on trophoblast cells (human leucocyte antigen, HLA-C). This interaction appears to block NK cytotoxicity against trophoblast cells. In this study, we investigated the expression of inhibitory and activating receptors in peripheral blood NK cells of women with recurrent spontaneous abortion (RSA) or implantation failures.
Method of study: CD56dim/CD16+, CD56bright/CD16− NK cells and CD56+/CD3+ NKT cells of women with RSA or in vitro fertilization (IVF) failures and normal controls were analyzed for the expression of CD158a, CD158b inhibitory KIRs or CD161-activating receptors, by flow cytometric analysis.
Results: CD158a and CD158b inhibitory receptor expression by CD56dim/CD16+ and CD56bright/CD16− NK cells were significantly decreased, and CD161-activating receptor expression by CD56+/CD3+ NKT cells was significantly increased in women with implantation failures when compared with normal controls.
Conclusions: An imbalance between inhibitory and activating receptor expression was found in NK cells of women with implantation failures. This imbalance may explain the adverse reproductive outcome.