HLA class I molecules expression: Evaluation of different immunocytochemical methods in malignant lesions

It is generally, accepted that human and experimental tumour cells can lose Major Histocompatibility Complex (MHC) class I molecules and this represen ts the major mechanism of tumour escape from T-cell immune responses. Never theless testing of HLA class I antigen expression in malignant lesions is n ot routinely used to evaluate the immunological conditions of the patients because of the pathologists' reluctance to utilise frozen tissue sections i n immunocytochemistry. We analysed the expressions of HLA class I molecule and beta (2)-microglobulin in normal and neoplastic tissues, comparing diff erent samples and methods. The expression of HLA receptors was studied in 7 brain tumours, 10 colon adenocarcinoma and 2 breast carcinoma by immunocyt ochemical technique. 4 normal tissues and peripheral blood mononucleated ce lls were analysed as positive control. The peroxidase staining method was p erformed on fresh imprints, frozen sections, formalin- fixed tissues and fi ne-needle aspirates. The results indicated that the best and simplest condi tions for the detection of HLA molecules were obtained using fresh imprints and fine-needle aspirates.