Commercially available antibodies against human and murine histamine H4-receptor lack specificity

Antibodies are important tools to detect expression and localization of proteins within the living cell. However, for a series of commercially available antibodies which are supposed to recognize G-protein-coupled receptors (GPCR), lack of specificity has been described. In recent publications, antisera against the histamine H-4-receptor (H4R), which is a member of the GPCR family, have been used to demonstrate receptor expression. However, a comprehensive characterization of these antisera has not been performed yet. Therefore, the purpose of our study was to evaluate the specificity of three commercially available H4R antibodies. Sf9 insect cells and HEK293 cells expressing recombinant murine and human H4R, spleen cells obtained from H4R-/- and from wild-type mice, and human CD20(+) and CD20(-) peripheral blood cells were analyzed by flow cytometry and Western blot using three commercially available H4R antibodies. Our results show that all tested H4R antibodies bind to virtually all cells, independently of the expression of H4R, thus in an unspecific fashion. Also in Western blot, the H4R antibodies do not bind to the specified protein. Our data underscore the importance of stringent evaluation of antibodies using valid controls, such as cells of H4R-/- mice, to show true receptor expression and antigen specificity. Improved validation of commercially available antibodies prior to release to the market would avoid time-consuming and expensive validation assays by the user.