Monoclonal antibodies for immunocytochemistry of progesterone receptors (PR) in various laboratory rodents, livestock, humans, and chickens: identification of two epitopes conserved in PR of all these species.

Over 90 mouse monoclonal antibodies have been raised against rabbit and human uterine progesterone receptor (PR). These antibodies, because of their specificity, are powerful tools with which to examine the localization, structure, and function of PR. A selection of 22 well characterized mABs was made to test their ability to give the best immunocytochemical staining of PR in various species. Comparative analysis of the antibodies led to the following conclusions. Li 417 (and, to a lesser extent, Let 126) was the best monoclonal in humans; Let 126 and Mi 60 were the most sensitive monoclonals in guinea pigs, rabbits, and monkeys. In sheep, sows, cows and mares as well as in rats and chickens Let 81 or Let 548 gave the best results (Let 126 was also effective in sows and mares, while Li 169 was also effective in sheep and cows). Two antibodies (Li 169 and Let 548) cross-reacted with PR in all of the species tested, including mammals and birds, and appeared to recognize two highly conserved antigenic sites. Remarkably, these conserved sequences are located in the highly variable N-terminal part of the receptor; they may, thus, be related to the still poorly understood function of this domain of the receptor.