Failure of histiocytosis X cells to express i blood group antigen

Expression of HLADR, I, i blood group antigen and T6 antigen were studied in Histiocytosis X cells and pulmonary alveolar macrophages using double labelling immunofluorescence technique or immuno-peroxidase procedure. Alveolar macrophages express simultaneously HLADR and i blood group antigen. Histiocytosis X cells, characterized by HLADR and T6 antigens, and by their ultra-structural marker do not express i antigen. These results confirm the hypothesis that histiocytosis X cells constitute a specialized sub-population of the mononuclear phagocyte system.