Anti-progesterone. Monoclonal antibody raised against position 11 of progesterone (Clone 1E11). It is very specific for progesterone.Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species. 

Binding of homologous and heterologous isoluminol- and enzyme-labelled progesterone conjugates to monoclonal antibodies, Jozef G. De Boever, Fotune Kohen, Eugene Bosmans Analytica Chimica Acta, Volume 290, Issues 1–2, 1994