HNK-1⁺ cells in non-Hodgkin's lymphoma: Lack of relation with transferrin receptor expression on malignant cells

It has been proposed that Natural Killer (NK) cell activity is involved in host defence against neoplasia, and that NK cells react with or recognize the transferrin receptor (TrR) on target cells. HNK-1 expression has been related to NK cell function. Therefore, in 118 cases of non-Hodgkin's lymphoma (NHL) we studied the occurrence and distribution of HNK-1+ cells by immunohistochemistry, and simultaneously assessed the expression of TrR on malignant cells. In NHL of intermediate or high grade malignancy there was uniform expression of TrR on malignant cells. In low grade malignancy NHL, only lymphocytic and lymphoplasmacytoid lymphomas were TrR negative, except for faint staining of proliferation centres. In 23 cases of follicular lymphoma, 9 showed the absence of HNK-1+ cells in neoplastic follicles. In 16/23 cases HNK-1+ cells were present around follicles or in interfollicular areas: 8 of these cases revealed a higher density of HNK-1+ cells at this site than inside the follicles. In 22/26 cases with high grade malignancy NHL, HNK-1+ cells were absent or present in small density, which is different from the presence in higher density in low grade malignancy NHL. We conclude that (i) TrR expression on NHL cells is not obligatory related with histological class or malignancy grade of the tumour, and that (ii) HNK-1+ cells are not universally present in areas of malignant cells, in particular in follicular lymphoma and in NHL of high grade malignancy.