Introduction: The exceptionality of endometrium, differentiating it from other epithelial tissues is related with its ability to regulate the number and activity of infiltrating immunological cells according to menstrual cycle phases. The aim of this study was a comparative evaluation of the number of CD56 positive cells, as well the analysis of CD69 antigen expression during decidualization.
Materials and methods: The expression of CD56 and CD69 antigens was analyzed using the immunohistochemistry method in 20 decidual tissue samples derived after curettage following spontaneous abortion and in 38 endometrial tissue samples obtained during hysterectomy performed because of benign myoma diagnosis. The endometrial tissue samples were divided regarding to the menstrual cycle phases. Following phases were distinguished: early proliferative, mid-proliferative, late proliferative, early secretory, mid secretory and late secretory.
Results: The higher CD56 positive cells were recognized in the endometrium during mid secretory cycle phase. The number of CD56 positive cells was significantly lower in endometrium, independent of menstrual cycle phase in comparison to endometrium following abortion. The expression of CD69 antigen was observed to increase beginning with early secretory cycle phase and remained at high level during the secretory cycle phase and the abortion.
Conclusions: The observed differences in the number of CD56 positive cells during decidualization without the changes in immune cells activity evaluated using CD69 antigen expression may indicate the participation of activated mononuclear cells in the normal development of pregnancy beginning with implantation.