Development and characterisation of an antibody for the immunohistochemical detection of inhibin/activin betaE (βE) in normal human ovarian and placental tissue

Inhibin/activin subunits are homologues to each other and belong to the transforming growth factor-beta (TGF-β) family of proteins. These proteins have been demonstrated to be disulphide-linked dimers, which have a common α-subunit but just one of two β-subunits, differentiated in inhibin A (α-βA) and in inhibin B (α-βB). Recently, an additional β-subunit has been identified, determined as βE and being primarily synthesized in liver tissue. However, since no antibody against the βE subunit is commercially available, limited data on histological immunodistribution of this inhibin subunit in gynaecological organs exist. Therefore, the aims of the present study were the synthesis and evaluation of a specific antibody against the inhibin-βE subunit. In this study, we describe the characterisation of a polyclonal antibody against the inhibin-βE subunit. This antibody demonstrated a specific reaction in both western blot analysis and immunohistochemistry. Moreover, we demonstrated positive immunolabelling in normal human ovary and placenta. The role of this novel subunit is intriguing, especially within the view that the other inhibin/activin subunits might have substantial functions in human reproduction and carcinogenesis. However, the function of this subunit in humans remains still unclear and warrants further research.