Proliferative activity and apoptosis of Langerhans histiocytes in eosinophilic granulomas as evaluated by MIB-1 and TUNEL methods

Aims - To identify the role played by apoptosis in tumour regression. Methods - The growth fraction and apoptotic cell loss of four cases of eosinophilic granuloma were investigated using monoclonal antibodies against Ki-67 proliferation marker (MIB-1) antigen and the TdT mediated dUTP-biotin 3'-OH nick end labelling (TUNEL) method. These data were then compared with the clinical growth rate. Results - Only the Langerhans histiocytic cells, which reacted positively with anti-S-100 protein antibody, were immunolabelled with antibodies to proliferating cell nuclear antigen and Ki-67 antigen (MIB-1). Many apoptotic figures of histiocytic cells were also detected in all cases by the TUNEL method. In a patient whose tumour clinically showed spontaneous regression, the TUNEL staining index gave a higher score than the MIB-1 staining index. Conclusions - The main cause of the spontaneous regression of the tumours was postulated to be programmed cell death (apoptosis).