[A study on HLA-Dr expression of brain tumor cells and mononuclear cell subsets infiltrating in these tumors].

Fourty-four primary brain tumors were studied by immunohistochemistry. 29 (67.2%) expressed HLA-Dr. The incidence and number of tumor cells positive for HLA-Dr correlated with the histological type of brain tumor and increased with the degree of malignancy. The mononuclear cells infiltrating in these tumors were mostly CD45ROT cells and macrophages. The former consisted mainly of CD4 and CD8 subsets. The numbers of CD45RO+ and CD8+ T cells in HLA-Dr-group were more than any of the HLA-Dr+, +2, +3 groups. The numbers of CD4 subset and macrophages were not affected by the level of HLA-Dr expression. These results suggest that the HLA-Dr expressed by brain tumor cells selectively inhibit CD8 subset which participates in immunoreaction against brain tumors in situ.