IMMUNOCYTOCHEMICAL STUDY OF LYSOSOMAL PROTEINS WITH A NEW MONOCLONAL-ANTIBODY DIRECTED AGAINST EPITHELIOID MACROPHAGES

A monoclonal antibody, EPI-I, was produced against macrophages in epit helioid granulomas induced in rat foot pads by muramyl dipeptide. This EPI-1 antibody reacted to lysosome-like structures in epithelioid mac rophages, peritoneal and pulmonary macrophages, and also in other tiss ues such as liver, testes, and kidneys. Western blot analysis of epith elioid granulomas, liver, testes, and kidneys revealed the same positi ve band of 62 kDa. Immunoelectron microscopic study of foot pad granul omas and hepatocytes demonstrated the EPI-I antigen located in lysosom es and autophagic vesicles, preferentially along their membranes. Thes e findings suggest that the EPI-1 antibody may recognize a novel antig en related to lysosomal membrane proteins in macrophages and other cel ls, which is useful for identifying lysosomes and their related struct ures.