[New endometrial modulators in early pregnancy]

Cytokines synthesized by the uterus or placenta include those thought to be produced exclusively by, or though to act on, cells of the lymphohematopoietic system. Although many of these cytokines are protein mediators of the immune system effector phase, in the female reproductive tract their principal target cells and sites of synthesis are non-lymphohematopoietic cells. During pregnancy, uterine epithelial cells, decidual cells and trophoblast appear to be major sources of the classic lymphohematopoietic cytokines. This suggests two not necessarily exclusive alternatives: that these cells are extensions of, or are involved in, regulating the immune system, or that these factors regulate growth and differentiation of uterine and embryonic tissues. This paper analyzes the sites of synthesis, targets and possible functions of the cytokines during early pregnancy.