Unique epitopes of lactoferrin expressed in human cytotrophoblasts involved in immunologic reactions, ,

Objective: Lactoferrin is an iron-binding protein that has been implicated in protection against infections and allogeneic recognition reactions and in the control of cell growth. We studied the biochemical characteristics and expression of the unique lactoferrin epitopes (LF1) in human placentas. Study Design: Immunohistologic studies of normal human term placentas were done by using monoclonal antibodies to LF1. Double-antibody experiments were done by using monoclonal antibodies to markers of inflammation (macrophages, human leukocyte antigen [HLA-DR]). LF1 was studied immunochemically by using lactoferrin fragments produced by the reaction of lactoferrin with trypsin or N-glycanase. Results: Anti-LF1 monoclonal antibodies reacted with most interstitial cytotrophoblasts in the basal plate and with villous cytotrophoblasts of some but not all chorionic villi. Cytotrophoblasts expressing LF1 were associated with large numbers of HLA-DR–reactive macrophages. Anti-LF1 monoclonal antibodies reacted with 2 distinct tryptic fragments of lactoferrin, and these reactivities were not affected by treatment with N-glycanase. Conclusion: Placental cytotrophoblasts express unique epitopes of lactoferrin (LF1). Such expression is increased in the presence of activated macrophages. This expression could be an extraembryonic response to inflammation and maternal allogeneic recognition as an effort to protect trophoblastic cells. The LF1 epitopes might represent conserved polypeptide epitopes on 2 homologous lobes of lactoferrin. (Am J Obstet Gynecol 1999;181:460-7.)