An immunohistochemical characterisation of the inflammatory cell infiltrate in benign and malignant prostatic disease.

The prostate gland is said to be immunologically privileged because it lacks afferent lymphatics and because of the immunosuppressive properties of seminal fluid. To elicit the presence or absence of an immune response within the diseased prostate gland, the infiltrate in prostate glands affected by hyperplasia or adenocarcinoma was phenotypically characterised, using immunohistochemical techniques. An infiltrate, composed mainly of T-lymphocytes (CD-3+), was demonstrated in all glands examined. No difference in the type, level of activation or degree of infiltration was found between those glands affected by hyperplasia (n = 20) and those affected by adenocarcinoma (n = 20). In the malignant cases, there was no correlation between grade (Gleason) or stage (TNM) and the type or degree of mononuclear cell infiltrate. Our findings suggest that the host response, in situ, to hyperplasia and adenocarcinoma is similar and may reflect the fact that the two diseases are often found concurrently in the same gland and in close proximity to one another. The infiltrate, therefore, is unlikely to represent a tumour specific immune response to tumour specific antigens. The significant infiltrate we have demonstrated, and its phenotypic characterisation, would not support the hypothesis that the prostate is immunologically privileged as has been suggested previously.