The CXCR4-STAT3-IL-10 Pathway Controls the Immunoregulatory Function of Chronic Lymphocytic Leukemia and Is Modulated by Lenalidomide

Chronic lymphocytic leukemia (CLL) cells possess regulatory functions comparable to those of normal B10 cells, a regulatory B cell subset that suppresses effector T-cell function through STAT3-mediated IL-10 production. However, the mechanisms governing IL-10 production by CLL cells are not fully understood. Here, we show that the CXC chemokine ligand 12 (CXCL12)–CXCR4–STAT3 axis regulates IL-10 production by CLL cells and their ability to suppress T-cell effector function through an IL-10 mediated mechanism. Knockdown of STAT3 significantly impaired the ability of CLL cells to produce IL-10. Furthermore, experiments to assess the role of lenalidomide, an immunomodulatory agent with direct antitumor effect as well as pleiotropic activity on the immune system, showed that this agent prevents a CXCL12-induced increase in p-S727-STAT3 and the IL-10 response by CLL cells. Lenalidomide also suppressed IL-10-induced Y705-STAT3 phosphorylation in healthy T cells, thus reversing CLL-induced T-cell dysfunction. We conclude that the capacity of CLL cells to produce IL-10 is mediated by the CXCL12–CXCR4–STAT3 pathway and likely contributes to immunodeficiency in patients. Lenalidomide appears to be able to reverse CLL-induced immunosuppression through including abrogation of the CXCL12–CXCR4–S727–STAT3-mediated IL-10 response by CLL cells and prevention of IL-10-induced phosphorylation of Y705-STAT3 in T cells.

Renal Mast Cell recruitment in MRL/lpr mice (173.28)

Mast cells (MC) are key effectors cells of the immune system. MC infiltration has been reported in a variety of renal diseases including lupus nephritis. Recently it has been argued that MCs are key contributors to a common pathway of progressive renal injury, however, the chemotaxic mechanism of renal MC recruitment are largely unknown. We observed a progressive age-depended MC infiltrate in kidneys of MRL/lpr mice. MRL/lpr bone marrow-derived MC (BMMC) had a high chemotatic capacity in response to MRL/lpr serum. In order to characterize the factors involved in MCs recruitment in MRL/lpr mice we performed expression array analysis in stimulated and un-stimulated MRL/lpr MCs. Serum stimulation increased BMMC expression of the integrin alpha E and chemokine receptors CCR5 and CXCR4. Kidney immunofluorescence staining confirmed these finding in situ. BMMC chemotaxis in vitro was enhanced in response to CCR5 ligands (MIP-1α and RANTES) and CXCR4 ligand (SDF-1) and was blocked by using a non-peptide chemokine receptor antagonist TAK-779. In vivo, TAK-779 significantly blocked the accumulation of renal MC in MRL/lpr mice. Our study indicate that the chemokine receptors CCR5 and CXCR4 and the integrin alpha E are important mediators of renal MC recruitment.