HORSE TROPHOBLASTS PRODUCE TUMOR-NECROSIS-FACTOR A BUT NOT INTERLEUKIN-2, INTERLEUKIN-4, OR INTERFERON-GAMMA

The distribution of four cytokines was analyzed in the endometrium and trophoblast of the horse between Days 30 and 55 of gestation. Endometrial tissues, invasive trophoblast (chorionic girdle), and noninvasive trophoblast (chorion and allantochorion) were examined separately. Cytokine expression was determined by amplification of specific mRNA via the reverse transcriptase-polymerase chain reaction (RT-PCR). Messenger RNA for interleukin 2 (IL-2), interleukin 4 (IL-4), and interferon gamma (IFN gamma) was detected in endometrial tissues, unstimulated peripheral blood lymphocytes, and control kidney tissue, but not in trophoblasts. Leukocytes resident in the endometrium or traversing the uterus via blood vessels might be the source of these cytokines. Endometrial tissues and invasive and noninvasive trophoblasts expressed mRNA for tumor necrosis factor alpha (TNF alpha). Immunoreactive TNF alpha protein was detected in different cell types of the endometrium and in the invasive and noninvasive trophoblast. The ubiquitous expression of TNF alpha by the endometrium and trophoblasts suggests that this cytokine might have an important role in regulating placental growth and differentiation or maternal leukocyte responses to trophoblasts. IL-2, IL-4, and IFN gamma might have important immunoregulatory roles within the endometrium.