Aim: Major histocompatibility complex (MHC) class II molecules (HLA-DR, -DP, -DQ) associate with peptides, derived from antigens, for presentation to CD4(+) T cells. Functional and adhesion assays have shown that CD4 interacts with MHC class II molecules, leading to enhanced responses of CD4(+) T cells after the activation of a specific tyrosine kinase. In the present study we examined the tissue expression of HLA-DR antigens and the quantitative variance of T4 lymphocytes in a series of 50 usual "endometrioid" adenocarcinomas and 35 conventional cervical squamocellular carcinomas.

Material-Methods: A three-step, avidin-biotin immunoperoxidase staining method was applied. As primary antibodies we used the TAL.1B5 monoclonal anti-human HLA-DR alpha chain antibody and the OPD4 mouse antihuman antibody which mainly identifies benign T4 lymphocytes.

Results: Twenty-four per cent of women with endometrial cancer were high immune responders, while the relative percentage in women with cervical cancer was 40%. These patients' tumours were of early clinical stages. HLA-DR determinants were predominantly expressed in membranes of stromal cells (i.e. macrophages-monocytes), usually around HLA-DR(+) lymphoid cells, as well as on endothelial cells. When the tumour stroma was rich in HLA-DR(+) cells, greater numbers of OPD4(+) lymphocytes aggregated. Epithelial elements, either cancerous or benign, were seldom HLA-DR(+); in these samples positive immunolabelling was often confined intercellularly and did not seem to enable an effective host immune response against neoplastic cells.

Conclusions: High expression of HLA-DR molecules in professional antigen presenting stromal cells may be used as a lymphocyte activation marker in endometrial and cervical carcinomas; this activation appears to be an early event in the evolution of invasive endometrial and cervical carcinomas.

Key words: Antigens HLA-DR, T4 lymphocytes, endometrial carcinoma, uterine cervical carcinoma.

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