The expression of class II MHC gene products by fallopian tube epithelium in pregnancy and throughout the menstrual cycle.

The expression of HLA class II antigens by human fallopian tube epithelium was investigated in ectopic tubal pregnancy, in normal early and full-term intrauterine pregnancy, and during the menstrual cycle. Monoclonal antibodies directed against non-polymorphic (DA6.231, CR3/43, B7/21) and polymorphic (DA6.147, DA6.164, anti-leu-10) determinants of the HLA-D locus were used in a standard indirect immunoperoxidase method on fresh cryostat sections of fallopian tube. In ectopic pregnancy the tube epithelium showed uniform, intense reactivity for DR, DP and DQ. A similar reaction pattern was observed in normal first-trimester pregnancy. At term, most epithelial cells were DR-, DP- and DQ-positive, but a few were DP- and DQ-negative. In fallopian tubes from non-pregnant individuals, a variable number of epithelial cells labelled for DR alpha and DR beta but there was essentially no reactivity for DP or DQ. These results suggest differential regulation of class II MHC gene expression by tube epithelial cells, possibly mediated by hormones and/or a trophoblast product.