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 represents the major mechanism of tumour escape from T-cell immune responses. Nevertheless testing of HL4 class I antigen expression in malignant lesions is not routinely used to evaluate the immunological conditions of the patients because of the pathologists' reluctance to utilise frozen tissue sections in immunocytochemisty. We analysed the expressions of HLA class I molecule and beta2-microglobulin in normal and neoplastic tissues, comparing different samples and methods. The expression of HLA receptors was studied in 7 brain tumours, 10 colon adenocarcinoma and 2 breast carcinoma by immunocytochemical technique. 4 normal tissues and peripheral blood mononucleated cells were analysed as positive control. The peroxidase staining method was performed on fresh imprints, frozen sections, formalin- fixed tissues and fine-needle aspirates. The results indicated that the best and simplest conditions for the detection of HLA molecules were obtained using fresh imprints and fine-needle aspirates.