Changes in Ia-like antigen expression on malignant human cells

Abstract

In human and in animal model tumor systems malignant cells may express allospecificities or types of histocompatibility antigens that are not detectable on their normal counterparts (Invernizzi and Parmiani 1975, Garrido et al. 1976, Pellegrino et al. 1976, Martin et al. 1977, Winchester et al. 1978, Wilson et al. 1979 a). Among them the appearance of Ia-like antigens on human melanoma cells (Winchester et al. 1978, Wilson et al. 1979 a) is of particular interest because of the possible role of these antigens in the interaction between host's immune system and tumor cells (Forni et al. 1975). In view of this finding we have investigated whether variations in expression of Ia-like antigens occur in other human tumors of nonlymphoid origin by testing surgically removed tumor specimens with monoclonal antibodies to Ia-like antigens in indirect immunofluorescence (IIF). Monoclonal antibodies Q 5/13 (MoAb Q S/13) to framework determinants of Ialike antigens were prepared and characterized as described (Quaranta et al. 1980). Tumor specimens, which were obtained from patients undergoing surgery in the Regina Elena Cancer Institute, Surgery Division, were immediately frozen in liquid nitrogen. Two consecutive 4 g cryostat sections from each tumor sample were fixed for 5 minutes in absolute acetone, which was shown by preliminary experiments not to effect the antigenicity of Ia-like antigens in tissue. One section was stained with Toluidine blue (0.1~o in phosphate-buffered saline) and the other was used as substrate in an IIF test with the anti-Ia-like antigen MoAb Q5/13 with an average concentration of 5 gg/ml and a fluorescein labeled (FITC) rabbit anti-mouse Ig antiserum (Meloy Laboratories, Springfield, Virginia) as second antibody. The FITC anti-mouse Ig xenoantiserum, which had fluorescein/protein ration of 3 and a protein concentration of 1.5 mg/ml, was preabsorbed with ABRH + red blood cells and with peripheral blood lymphocytes (PBL) of chronic lymphocytic leukemia (CLL) patients, which express high levels of Ia-like antigens. The specificity of the strain observed on different tumor-tissue substrates was assessed by direct staining with the FITC-labeled antiserum and by indirect staining with MoAb Q5/13 preabsorbed extensively with an equal volume of PBL from CLL patients or