Localization of IGF-I and IGF-II mRNA in the bovine uterus and elongating embryo

Abstract

Intraepithelial lymphocytes are a constant feature of ruminant uterine epithelium. Light microscope quantitation on semithin sections of resin embedded perfused material from pregnant and non-pregnant cows shows that although the proportion of large granular lymphocytes to non-granular lymphocytes in interplacentomal areas increases during pregnancy, the total number of lymphocytes in these areas remains at a similar level. However all types of lymphocytes are eliminated from the caruncular uterine epithelium of the cow by 28 days of pregnancy at the initiation of placentomal development. Despite the subsequent enormous growth in area of this region during pregnancy, no lymphocytes are found in the bovine placentomal cellular uterine epithelium. This pattern is similar to that in the ewe and goat although in these species the placentomal uterine epithelium is modified to maternofetal hybrid syncytial plaques. However, in the deer, a similar cellular placentomal epithelium has numerous intraepithelial lymphocytes and large granular lymphocytes are closely associated with fetomaternal hybrid trinucleate cells formed by binucleate cell migration throughout pregnancy. Cow interplacentomal large granular lymphocytes and trinucleate cells show similar apposition but the formation and fate of cow placentomal trinucleate cells does not involve lymphocytes. Since the caruncular (placentomal) area is 10–20 times that of the intercaruncular this suggests a very different function for intraepithelial lymphocytes in the deer compared with the other ruminant species.