CXCL12 is a costimulator for CD4+ T-cell activation and proliferation in patients with chronic lymphocytic leukemia

BORGE MERCEDES; NANNINI PAULA; MORANDE PABLO; JANCIC CAROLINA; ZANETTI SAMANTA; BISTMANS ALICIA; BEZARES FERNANDO; GIORDANO MIRTA; GAMBERALE ROMINA

Houston

Workshop; International Workshop on Chronic lymphocytic leukemia. 2011, Houston, USA; 2011

iwCLL Consortium

B-cell chronic lymphocytic leukemia (CLL) cells proliferate in lymphoid tissues in close contact with activated T cells, stromal cells, and accessory myeloid cells, such as nurse-like cells (NLC), which favor CLL cell survival and proliferation. CXCL12 is a highly conserved chemokine produced by stromal cells and NLC; CXCR4, its main receptor, was shown to induce CLL4 and T-cell migration and leukemic cell activation and survival. The aim of this study was to determine whether CXCL12 enhances activation and proliferation of T cells in patients with CLL. Peripheral blood mononuclearcells from patients with CLL were cultured for 2 hours with or withoutrecombinant human CXCL12 (rhCXCL12), then transferred tocell culture plates with immobilized anti-CD3 monoclonal antibodies(mAb). After 24 hours of culture, expression of the activationmarkers CD25, CD69, and CD154 on CD4 T cells was evaluatedby fluorescence-activated cell sorting. We found that the combinationof anti-CD3 and rhCXCL12 significantly increased the expressionof all activation markers beyond that induced by anti-CD3alone (p 0.01, n 18). No significant differences were observedwhen samples were segregated according to ZAP-70 or CD38 expression.The CXCL12-mediated enhancement of CD4 T-cell activationwas similarly observed when we performed the experiments withpurified T cells and was blocked by anti-CXCR4 mAb, suggestingthat this receptor is necessary for T-cell costimulation by CXCL12.Moreover, we found that rhCXCL12 enhances interferon- production(p 0.01, n 18) and proliferation (p 0.01, n 10) ofactivated CD4 T cells from patients with CLL beyond that inducedby anti-CD3 alone. Of note, leukemic cell activation (p0.05, n10) and proliferation (p0.05, n10) were enhanced by activatedT cells in the presence of rhCXCL12. In addition, autologous NLCincreased the activation (p 0.01, n 10) and proliferation (p 0.05, n 5) of CD4 T cells from patients with CLL, in partthrough a CXCR4-dependent mechanism. Our results prompted usto hypothesize that CXCL2 production by the lymphoid tissue microenvironmentin CLL patients may play a key dual role for T-cellphysiology, functioning not only as a chemoattractant5 but also as acostimulatory factor for activated T cells. Because it was clearly demonstratedthat the activation of T cells from patients with CLL iscritical in the disease,6 identifying the mechanisms whereby T cells respond to microenvironmental activating and proliferating signalscould reveal novel targets for therapy.