Class I and II HLA antigen distribution in normal mucosa, adenoma and colon carcinoma: relation with malignancy and invasiveness.

HLA class I and II antigen expression was studied in normal mucosa, adenoma and colon carcinoma. Alkaline phosphatase anti-alkaline phosphatase (APAAP) staining techniques were used in cryostatic sections with anti-HLA-ABC and DR,DP,DQ monoclonal antibodies. All normal mucosa were intensely positive for HLA class I antigen expression, while failing to express class II molecules, except in mucosa adjacent to tumors (15/19 cases). All adenomatous polyps expressed HLA class I antigen, while the intensity of class II expression (DR greater than DQ greater than DP) was paralleled by the degree of dysplasia. In colon carcinoma, the loss of class I expression was seen in 4 out of 32 cases, and class II expression was found to be heterogeneous in 16 of these 32 cases (DR greater than DP greater than DQ). No relationship was noted between class II expression and degree of differentiation. However a correlation was seen between HLA-DR antigen expression and degree of invasiveness, mononuclear infiltrate and prognosis, according to Jass's criteria.