Immunohistochemical studies on the expression of HLA class I antigens in renal cell carcinoma: comparison of primary and metastatic tumor tissue.

HLA class I expression was studied in 43 specimens of normal renal tissue, 48 primary renal cell carcinomas (RCCs), and 12 metastases by immunofluorescence, using two different monoclonal antibodies (MoAbs; IOT2c, W6/32). Homogenous staining of all normal renal tissues was observed, as expected. From the panel of 48 renal tumors, 40 had a strong expression of HLA class I antigens when tested with both MoAbs, 7 tumors had only weak expression of HLA class I and were regarded as 'HLA class I negative', and 1 tumor showed homogenous staining when tested with one MoAb (IOT2c) but was negative when the other was used (W6/32). This was the only case in which different results with the two MoAbs were found. Reduced expression of HLA class I antigens was observed in 5/12 metastases, and in 1 metastasis no expression of HLA class I could be seen. The staining chartacteristics of 10 metastases in comparison with the respective primary tumors were as follows: same HLA class I score 7/10; loss of HLA class I 3/10; gain of HLA class I 0/10. In RCC, a complete loss of HLA class I expression is a rare phenomena, which was observed in 0/48 primary tumors and in 1/12 metastases. Reduced expression of HLA class I antigens occurs in about 15% of primary tumors but is more frequent (50%) in metastases; however, if this is relevant for cytotoxicity by T lymphocytes is unknown.