In this study, we analyzed the influence of mesenchymal stromal cells derived from lymph nodes of non-Hodgkin's lymphomas, on effector functions and differentiation of Vdelta (6)2 T lymphocytes. We show that: i) lymph-node mesenchymal stromal cells of non-Hodgkin's lymphoma inhibit NKG2D-mediated lymphoid cell killing, but not rit-uximab-induced antibody-dependent cell-mediated cytotoxicity, exerted by V62 T lymphocytes; ii) pre-treatment of mesenchymal stromal cells with the aminobisphosphonates pamidronate or zoledronate can rescue lymphoma cell killing via NKG2D; iii) this is due to inhibition of transforming growth factor-p and increase in interleukin-15 production by mesenchymal stromal cells; iv) aminobisphosphonate-treated mesenchymal stromal cells drive V62 T-lym-phocyte differentiation into effector memory T cells, expressing the Thelper1 cytokines tumor necrosis factor-a and interferon-y. In non-Hodgkin's lymphoma lymph nodes, V62 T cells were mostly naïve; upon co-culture with autologous lymph-node mesenchymal stromal cells exposed to zoledronate, the percentage of terminal differentiated effector memory V62 T lymphocytes increased. In all non-Hodgkin's lymphomas, low or undetectable transcription of Thelper1 cytokines was found. In diffused large B-cell lymphomas and in a group of follicular lymphoma, transcription of transforming growth factor p and interleukin-10 was enhanced compared to non-neoplastic lymph nodes. Thus, in non-Hodgkin lymphomas mesenchymal stromal cells interfere with V62 T-lymphocyte cytolytic function and differentiation to Thelper1 and/or effector memory cells, depending on the prominent in situ cytokine milieu. Aminobisphosphonates, acting on lymph-node mesenchymal stromal cells, can push the balance towards Thelper1/effector memory and rescue the recognition and killing of lymphoma cells through NKG2D, sparing ritux-imab-induced antibody-dependent cell-mediated cytotoxicity.
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