Monocytes and T cells cooperate to favor normal and follicular lymphoma B-cell growth: role of IL-15 and CD40L signaling


Interleukin-15 (IL-15) has been extensively studied for its role in the survival and proliferation of NK and T cells through a unique mechanism of trans-presentation by producer cells. Conversely, whereas activated B cells have been described as IL-15-responding cells, the cellular and molecular context sustaining this effect remains unexplored. In this study, we found that, whereas human B cells could not respond to soluble IL-15, monocytes and lymphoid tissue-derived macrophages but not stromal cells efficiently trans-present IL-15 to normal B cells and cooperate with T-cell-derived CD40L to promote IL-15-dependent B-cell proliferation. Furthermore, CD40L signaling triggers a Src-independent upregulation of STAT5 expression and favors a Src-dependent phosphorylation of STAT5 in response to IL-15. In follicular lymphoma (FL), immunohistochemical studies reported a strong relationship between malignant B cells, infiltrating macrophages and T cells. We show here an overexpression of IL-15 in purified tumor-associated macrophages, and STAT5A in purified tumor B cells. Moreover, FL B cells respond to IL-15 trans-presented by monocytes/macrophages, in particular, in the presence of CD40L-mediated signaling. This cooperation between IL-15 and CD40L reinforces the importance of tumor microenvironment and unravels a mechanism of FL growth that should be considered if using IL-15 as a drug in this disease.

DOI: 10.1038/leu.2011.179
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@article{Epron2012MonocytesAT, title={Monocytes and T cells cooperate to favor normal and follicular lymphoma B-cell growth: role of IL-15 and CD40L signaling}, author={G Epron and Patricia Am{\'e}-Thomas and J{\'e}r{\^o}me Le Priol and C{\'e}line Pangault and J{\'e}r{\^o}me Dulong and Thierry Lamy and Thierry Fest and Karin Tarte}, journal={Leukemia}, year={2012}, volume={26}, pages={139-148} }