Cross reactivity of a monoclonal pan T-cell antibody (anti-Leu 4) with prostate epithelium

Cross reactions between monoclonal T-cell antibodies and non-lymphoid tissues have rarely been reported. In this study 28 samples of prostatic tissue obtained at the time of autopsy or surgery, two samples of metastatic prostatic carcinoma and a series of other tumours were snap frozen and sections reacted with a series of monoclonal antibodies directed against the following antigens: Leu 1, Leu 4, T3, T8, T4, T11 and B4. Reactions were detected with an indirect immunofluorescent method. In 10 of 11 normal prostates, 15 of 15 with nodular hyperplasia and 3 of 4 prostatic adenocarcinomas a strong positive reaction occurred with anti-Leu 4. All other antibodies tested were negative. Other tumours tested, including primary carcinomas of lung (2), kidney (3), stomach (1), colon (1), pancreas (1), breast (2), urinary bladder (1), esophagus (1), larynx (1) and malignant melanoma (2), were negative with all antibodies. This is, to our knowledge, the first report of cross reactivity between a monoclonal pan T-cell antibody and epithelium. This cross reaction may be related to a shared antigen between T-cells and prostate epithelial cells or, more likely, it represents reactivity with a shared epitope. Knowledge of this reaction will prevent possible misinterpretations in the evaluation of undifferentiated neoplasms.