Immunocytochemistry with monoclonal anti-immunoglobulin as a developing reagent: application to immunoperoxidase staining and radioimmunocytochemistry.

The development of two monoclonal antibodies for use as second antibodies in immunocytochemistry is described. The antibodies are produced by mouse X mouse hybrid myelomas, and are both of the IgG type. The two antibodies, RB23 and ND13, were used to detect neurophysin by three-step peroxidase-antiperoxidase (PAP) immunostaining, and were "internally labeled" with 3H-lysine for the radioimmunocytochemical localization of neurophysin, substance P, and tyrosine hydroxylase using rabbit first antibodies. The binding sites of RB23 and ND13 on the rabbit IgG antibodies were determined by solid-phase radioimmunoassay, using allotype-specific rabbit serum to compete with RB23 and ND13. It was found that both RB23 and ND13 are directed against the B4 kappa-light-chain allotype. The immunocytochemical localization of adrenocorticotropic hormone and somatostatin with rabbit primary antibodies was not achieved with RB23 or ND13, and it is proposed that these antibodies are not of the B4 allotype. The findings demonstrate that monoclonal second antibodies can be useful general reagents for conventional immunocytochemistry as well as for radioimmunocytochemistry. Furthermore, allotype-specific monoclonal second antibodies may prove useful in the simultaneous immunohistochemical localization of more than one antigen in a given tissue section.