[Granulated CD56 lymphocytes of decidual tissue]

The reproduction is a complex mechanism wich is subtly immunoregulated since the semiallogenic fetus is not rejected by the mother. At the feto-maternal tissue interface, where fundamental mechanisms of tolerance occur, a large and unusual lymphocytes population takes place. These cells recruited during the earlier stages of pregnancy are very granulated and express brightly the N-CAM molecule (or CD56) with numerous adhesion and activation molecules. Nevertheless, they seem fonctionnally inactivated. They phenotypically belong to the peripheral blood minor fraction of NK cells which are CD56++CD16-CD3-. Although their function in the establishment of the gestation is not clearly known, because of their phenotypical heterogeneity, they may have two distinct functions: cytotoxicity and suppression. Their cytokine pattern, preferentially of the Th1 type, inform us about their potential functions and their interactions with other cells populations in this tissue, allowing us to understand the main mechanism in the establishment of the pregnancy.