C. Montero, D. Segura, M. Gutiérrez
European journal of histochemistry : EJH
A study of the influence of three salts of monovalent cations (Nacl, KCl, and CsCl) and three salts of divalent cations (MgCl2.6H2O, anhydrous CaCl2, and SrCl2.6H2O), on the specific reaction between human hGH and three of its monoclonal antibodies has been carried out, using human pituitary glands obtained at autopsy as a model system. This study is an attempt to find out the physico-chemical laws ruling the immunohistochemical reaction in the special circumstance of fixed specimens, where the antigen (Ag) is immobilized in the tissue substrate, while the antibody (Ab) is mobile. Our interpretation of the results points to a reaction of the salts with side groups of aminoacids in the paratope (specific saline effect) and a mass salt effect on the reaction kinetic proper that is dependent on the salt concentration. The high affinity coefficient of the in situ Ag-Ab reaction is shown, at the immunohistochemical level, by the high molarity necessary to make the reaction negative. Also, it seems there is a direct relationship between the critical molarity values obtained and the affinities of the monoclonal antibodies used in this study.