Immunohistochemical localization of human alpha 2Macroglobulin in connective tissue.

The localization of alpha 2macroglobulin (alpha 2M) has been examined by an indirect immunofluorescent technique in frozen sections of various human tissues. The results indicate that alpha 2M is present only in connective tissues and blood. The outer medulla of the kidney and the submucosa of the gut showed the strongest reaction. Epithelia or endothelial cells were unreactive. In liver, only the Kupffer cells were stained. These results were confirmed withe the immunoperoxidase technique and by the study of tissue extracts in crossed immunoelectrophoresis (CIE). As a positive control a polyspecific antiserum prepared against whole human fibroblasts as well as anti-albumin were used. Our findings are interpreted in the light of the observations that alpha 2M is synthesized and selectively ingested by fibroblasts.