We demonstrated that whereas exogenous IL-15 promoted the survival of unpurified normal B cells, resting purified B cells could not VX-680 respond to this cytokine. Nonetheless, after CD40-triggering or coculture with autologous T cells, normal and FL-derived B cells became responsive to IL-15 that enhanced their proliferation, in association

with a phosphorylation of STAT5. Normal and FL B-cell growth was also increased when cocultured with monocytes and this feeder effect was reinforced by IL-15. Furthermore, targeting IL15 and IL15RA in monocytes by siRNA decreased monocyte-mediated B-cell growth. Specific depletion of CD14pos cells among tonsil cells decreased normal B-cell growth in presence or not of IL-15, confirming

the essential role played by myeloid cells in this context. Finally, confocal microscopy revealed the presence of IL-15RA at the cell interface between monocytes and B cells. Collectively, these data depict for the first time IL-15 as a B-cell growth factor within normal and FL B-cell niches and describe a potent new therapeutic target. O52 Anti-Tumor Treatment of Tumor-Bearing Immunocompetent Mice with Anti-CD20 mAb Induces an selleck Adaptive Immune Response that can be Strengthened by IL-2 Infusion Riad Abes 1,2 , Emmanuelle Gelize2, Jean-Luc Teillaud2 1 Laboratoire Français du Fractionnement et des Biotechnologies (LFB), Paris, France, 2 Team 14 Antibody Technology, INSERM U872 / Cordeliers Research Center; Pierre & Marie Curie University, UMR S 872; Paris Descartes University, UMR S 872, Paris, France The long-lasting responses observed in some lymphoma patients treated with rituximab NSC23766 mouse suggests that this antibody

induces an anti-tumor the immune response. We have investigated whether anti-CD20 treatment of CD20+ tumor bearing mice can trigger a adaptive immune response and whether it is possible to potentiate it by subsequent IL-2 infusion. C57Bl/6 mice were i.v. injected with EL4 tumor cells expressing human CD20 and treated with i.p. injections of the anti-CD20 mouse mAb CAT-13. Whereas all untreated animals died before Day 35, about 60–70% of CAT-13-treated mice survived. The surviving mice were then challenged at Day 70 by a new i.v. injection of either EL4-huCD20 or EL4 cells without any mAb treatment. All EL4-challenged-mice died before Day 26, while about 50–60% of EL4-huCD20-challenged mice were still alive at Day 70. Furthermore, a single i.v. injection of spleen cells isolated from these surviving animals into naive recipients injected with EL4-huCD20 cells 24 h later was sufficient to protect the latter animals.These data suggest that anti-CD20 mAb treatment induces a long-lasting adaptive immune response.