Demonstration of Fey receptors in human endometrium

Cryostat sections of human endometrium bound sheep erythrocytes (E) sensitized with rabbit IgG antibody (A), (EA). Unsensitized E were not bound. Native, heat‐aggregated IgG and Fc fragments of IgG inhibited the binding of EA, whereas IgM, IgA and F(ab’) 2 fragments of IgG did not. The data indicate the presence of receptors for the Fc part of IgG (FcR). Using immune complexes of horseradish peroxidase (HRP) and rabbit IgG antibodies to HRP and monoclonal antibodies (mAbs), FcR were located to the glandular epithelial and endothelial cells, macrophages and predecidual cells of the stroma. These structures were also stained by mAbs against all three FcR classes and a 40‐kD low affinity placental FcR. Preliminary results indicate that the expression of FcR varies during different stages of the menstrual cycle. FcR in the endometrium may play a role in local immunoregulation necessary for nidation and development of the blastocyst.