Fifty eight large bowel adenocarcinomas and 20 adenomas were studied i
mmunohistochemically, using fresh frozen tissue sections, with regard
to lymphocyte subpopulations (CD3, CD4, CD8, CD19, and CD20) in the in
flammatory infiltrate and to expression of human leucocyte antigens (H
LA-ABC, HLA-AZ, and HLA-DR). The findings were related to differentiat
ion and Dukes's stage of carcinoma. The inflammatory infiltrate was fo
und to have a phenotype that remained constant irrespective of the int
ensity of the inflammation. CD4 and CD3 positive cells predominated wi
th fewer CD8 positive cells and a scanty diffuse CD19/20 positive cell
population. CD19/20 follicular aggregates were common at the advancin
g margin of the carcinomas. There was no significant association with
Dukes's stage, differentiation or HLA status. HLA changes (ABC loss, A
2 loss, and DR gain) were associated with differentiation, being more
common and more extensive in poorly differentiated carcinomas. HLA-A2
loss was also associated with stage of progression of carcinoma. Infla
mmation associated with adenomas was found to have a similar phenotype
to that associated with carcinomas. HLA changes in adenomas were unco
mmon, being seen in only one of our 20 cases.