Monoclonal antibody against L-histidine decarboxylase for localization of histaminergic cells

The immunochemical and immunohistochemical properties of a monoclonal antibody (Mab HI 113-12) developed in mice against a partially purified preparation of rat gastric L-histidine decarboxylase (HD) were studied. The Mab recognised the HD activity from the antigen and from crude tissue extracts with a high histamine (HA)-synthesizing capacity (stomach, hypothalamus, striatum, mastocytoma). In contrast, neither a bacterial HD nor other decarboxylases (glutamic and DOPA decarboxylases) were immunoprecipitated. In preliminary immunohistochemical studies, staining of the cytoplasm of mastocytoma as well as of hypothalamic neurons, particularly magnocellular ones in the mamillary region, were observed. The latter presumably correspond to the cells of origin of a long ascending histaminergic pathway.