Anti-substance P anti-idiotypic antibodies modulate the secretory process in the rat parotid gland in vitro

Anti-idiotypic antibodies (anti-Id) obtained in rabbits in response to immunization with polyclonal anti-substance P antibodies (anti-SP) were shown to bind specifically and with high affinity to membranes from rat parotid gland cells. Whereas substace P (SP) was unable to displace anti-Id from membrane binding sites, anti-Id partly inhibited the binding of radiolabelled substance P. Like substance P, anti-Id were able to trigger protein secretion by parotid cells, i.e. to behave as physiological agonists of the neuropeptide. Under our experimental conditions, the biological effects of both ligands appear to be additive. Unlike substance P, however, anti-Id dir not potentiate the secretory responses induced by a β-adrenoceptor agonist. Taken together, the present results might indicate that anti-Id interact with epitope(s) at or/and near he peptide-combining site on the substance P receptor. These data demonstrate further the possibility of raising pharmacologically active anti-receptor antibodies through the immunological anti-idiotypic approach.