Expression pattern of immunosurveillance-related antigen in adult T cell leukaemia/lymphoma.

Adult T cell leukaemia/lymphoma (ATLL) is an aggressive malignancy with a poor prognosis. Human leucocyte antigen (HLA) and β2 microglobulin (β2M) serve as key molecules in tumour immunity, and their expression is reduced frequently in tumour cells. Programmed cell death (PD)-1/PD-ligand1 (PD-L1) interactions play a role in escape of tumour cells from T cell immunity. Therefore, this study aimed to determine the clinicopathological relevance of HLA and β2M expressions in ATLL cells and PD-L1 expression in lymphoma or stromal cells and predict the overall survival of patients with ATLL. We analysed a total of 123 biopsy samples from patients newly diagnosed with ATLL by using immunohistochemical analysis. Of the patients enrolled, 91 (74%) were positive for HLA (in cell membrane, 60 patients), 89 (72%) were positive for β2M (in cell membrane, 54 patients) and 48 (39%) were positive for both HLA and β2M in the cell membrane (HLAm+ β2Mm+ ). No significant clinical differences other than prognosis were found between the HLAm+ β2Mm+ group and the other groups. Immunophenotypical evaluation revealed significantly higher rates of CD30-positive lymphoma cells (P = 0.003) and PD-L1-positive stromal cells in microenvironments (miPD-L1high ) (P = 0.011) of the HLAm+ β2Mm+ group than in the other groups. The HLAm+ β2Mm+ group had a significantly better prognosis that the other groups (P = 0.0096), and patients showing HLAm+ β2Mm+ with miPD-L1high had the most favourable prognosis among all groups. The membranous expression of HLA and β2M is likely to reflect the immune response and would be useful to predict prognosis before starting ATLL therapy.