A COMPARISON OF FLOW-CYTOMETRY AND IMMUNOHISTOCHEMISTRY IN HUMAN COLORECTAL CANCERS

In human colorectal cancer it has been reported that some tumours lack the HLA-ABC antigens. This has been interpreted as reflecting tumour escape from the immune system. Earlier data have been obtained by immu nohistochemistry. In this study, we compared the expression of HLA-ABC , HLA-DR, CD80 (B7-1) and CD54 (ICAM-1) in 20 tumours using both a con ventional immunohistochemistry two-layer technique and multiparameter flow cytometry, gating on an epithelial cell marker. Colorectal cancer tissue used in flow cytometry was dissociated with collagenase, deoxy ribonuclease and hyaluronidase. The intensity of expression of HLA-ABC , HLA-DR and CD80 was unaffected by the enzymes, but CD54 was decrease d by 30%. The reproducibility of flow cytometry was good. Microscopy o f sections revealed that about 5% of each tumour sample consisted of n ormal epithelium, but even after correction for this, flow cytometry w as superior to immunohistochemistry in 33 out of 80 cases, and showed that rumours described as HLA-ABC negative by immunohistochemistry wer e in fact weakly positive for HLA-ABC. We conclude that flow cytometry and immunohistochemistry are complementary, and that flow cytometry i s superior to immunohistochemistry for detecting antigens/epitopes pre sent in low amounts.