: Chemokines are a family of proteins that chemoattract and activate cells by interacting with specific receptors on the surface of their targets. The chemokine stromal cell‐derived factor 1, (SDF1), binds to the seventransmembrane G protein‐coupled CXCR4 receptor and acts to modulate cell migration, differentiation, and proliferation. CXCR4 and SDF1 are reported to be expressed in various tissues including brain. Here we show that SDF1 and CXCR4 are expressed in cultured cortical type I rat astrocytes, cortical neurons, and cerebellar granule cells. In cortical astrocytes, prolonged treatment with lipopolysaccharide induced an increase of SDF1 expression and a down‐regulation of CXCR4, whereas treatment with phorbol esters did not affect SDF1 expression and down‐modulated CXCR4 receptor expression. We also demonstrated the ability of human SDF1α (hSDF1α) to increase the intracellular calcium level in cultured astrocytes and cortical neurons, whereas in the same conditions, cerebellar granule cells did not modify their intracellular calcium concentration. Furthermore, in cortical astrocytes, the simultaneous treatment of hSDF1α with the HIV‐1 capside glycoprotein gp120 inhibits the cyclic AMP formation induced by forskolin treatment.

Background: CTLA-4 (Cytotoxic T lymphocyte antigen-4) is traditionally known as a negative regulator of T cell activation. The blocking of CTLA-4 using human monoclonal antibodies, such as Ipilimumab, is currently used to relieve CTLA-4-mediated inhibition of anti-tumor immune response in metastatic melanoma. Herein, we have analyzed CTLA-4 expression and Ipilimumab reactivity on melanoma cell lines and tumor tissues from cutaneous melanoma patients. Then, we investigated whether Ipilimumab can trigger innate immunity in terms of antibody dependent cellular cytotoxicity (ADCC) or Tumor Necrosis Factor (TNF)-α release. Finally, a xenograft murine model was set up to determinein vivothe effects of Ipilimumab and NK cells on melanoma.Methods: CTLA-4 expression and Ipilimumab reactivity were analyzed on 17 melanoma cell lines (14 primary and 3 long-term cell lines) by cytofluorimetry and on 33 melanoma tissues by immunohistochemistry. CTLA-4 transcripts were analyzed by quantitative RT-PCR. Soluble CTLA-4 and TNF-α were tested by ELISA. Peripheral blood mononuclear cells (PBMC), NK and γδT cells were tested in ADCC assay with Ipilimumab and melanoma cell lines.TNF-α release was analyzed in NK-melanoma cell co-cultures in the presence of ipilimumab.In vivoexperiments of xenotransplantation were carried out in NOD/SCID mice. Results were analyzed using unpaired Student’s t-test.Results: All melanoma cell lines expressed mRNA and cytoplasmic CTLA-4 but surface reactivity with Ipilimumab was quite heterogeneous. Accordingly, about 2/3 of melanoma specimens expressed CTLA-4 at different level of intensity.Ipilimumab triggered, via FcγReceptorIIIA (CD16), ex vivo NK cells as well as PBMC, IL-2 activated NK and γδT cells to ADCC of CTLA-4⁺melanoma cells. No ADCC was detected upon interaction with CTLA-4^-FO-1 melanoma cell line. TNF-α was released upon interaction of NK cells with CTLA-4⁺melanoma cell lines. Remarkably, Ipilimumab neither affected proliferation and viability nor triggered ADCC of CTLA-4⁺T lymphocytes. In a chimeric murine xenograft model, the co-engraftment of Ipilimumab-treated melanoma cells with human allogeneic NK cells delayed and significantly reduced tumor growth, as compared to mice receiving control xenografts.Conclusions: Our studies demonstrate that Ipilimumab triggers effector lymphocytes to cytotoxicity and TNF-α release. These findings suggest that Ipilimumab, besides blocking CTLA-4, can directly activate the elimination of CTLA-4⁺melanomas.