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

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

houston, texas

Workshop; XIV International Workshop on CLL.; 2011

B cell chronic lymphocytic leukemia (CLL) cells proliferate in lymphoid tissues in closecontact with activated T cells, stromal cells and accessory myeloid cells, such as nurse-like cells(NLC) which favor CLL cell survival and proliferation [1-3]. CXCL12 is a highly conservedchemokine produced by stromal cells and NLC [3] and CXCR4, its main receptor, was shown toinduce CLL [4] and T cell migration [5] and leukemic cell activation and survival [4]. The aim of thisstudy was to determine whether CXCL12 may enhance the activation and proliferation of T cellsfrom CLL patients. Thus, peripheral blood mononuclear cells from CLL patients were cultured for 2hours with or without recombinant human CXCL12 (rhCXCL12), then transferred to cell cultureplates with immobilized anti-CD3 mAb and after 24hs of culture, the expression of the activationmarkers CD25, CD69 and CD154 on CD4+ T cells was evaluated by FACS. We found that thecombination of anti-CD3 and rhCXCL12 significantly increased the expression of all activationmarkers beyond the one induced by anti-CD3 alone (p<0.01, n=18). No significant differenceswere observed when samples were segregated according to ZAP-70 or CD38 expression. TheCXCL12-mediated enhancement of CD4+ T cell activation was similarly observed when weperformed the experiments with purified T cells and was blocked by anti-CXCR4 mAb suggestingthat this receptor is necessary for the T cell costimulation by CXCL12. Moreover, we found thatrhCXL12 enhances IFN production (p<0.01, n=18) and proliferation (p<0.01, n=10) of activatedCD4+ T cells from CLL patients beyond that one induced by anti-CD3 alone. More interestingly,leukemic cell activation (p<0.05, n=10) and proliferation (p<0.05, n=10) was enhanced by activatedT cells in the presence of rhCXCL12. In addition, autologous NLC increased the activation (p<0.01,n=10) and proliferation (p<0.05, n=5) of CD4+ T cells from CLL patients partially through a CXCR4-dependent mechanism. Altogether, our results prompted us to hypothesize that CXCL2 productionby lymphoid tissue microenvironment in CLL patients may play key dual role for T cell physiology,functioning not only as a chemoattractant [5] but also as a costimulatory factor for activated T cells.Since it was clearly demonstrated that the activation of T cells from CLL patients is critical in thedisease [6], identifying the mechanism(s) whereby T cells respond to microenvironmentalactivating and proliferating signals could reveal novel targets for therapy.