Il-6 mediates galectin-8 costimulatory activity of antigen-specific CD4T cell response

CARABELLI, JULIETA; PRATO, CECILIA ARAHÍ; SANMARCO, LILIANA MARÍA; AOKI, MARIA PILAR; CAMPETELLA, OSCAR; TRIBULATTI, MARÍA VIRGINIA

Buenos Aires

Congreso; Reunion Conjunta de Sociedades de Biociencias; 2017

Galectin-8 (Gal-8) is a mammalian lectin endowed with the ability to costimulatethe antigen-specific immune response. IL-6 is a pleiotropic cytokinethat plays an important role in the regulation of antigen-specific T cell response.In the present study, we aimed to elucidate whether IL-6 was mediating Gal-8costimulatory effect on antigen-specific CD4T cells. Firstly, we quantified IL-6 byELISA in supernatants from DO11.10TCROVA mouse splenocyte cultures,stimulated with the cognate peptide OVA (OVA), Gal-8 or the combination ofboth. Notably, IL-6 was significantly increased in the conditioned media fromGal-8- or Gal-8 plus OVA-treated cells but not from OVA only-treated cells,where IL-6 was present at the same level as in untreated cells. Next, to assessif IL-6 is involved in Gal-8 costimulatory effect, splenocytes were stimulated, asbefore, but in the presence of an IL-6-neutralizing monoclonal antibody or amatching isotype control, and T cell proliferation was determined. Interestingly,IL-6 neutralization specifically precluded Gal-8 costimulatory activity but did notaffect antigen-specific T cell response. To identify those cells that produce IL-6in response to Gal-8, intracellular IL-6 was determined by FACS in Gal-8-stimulated BALB/cJ splenocytes. We found that both CD11c+ and CD11b+ cellsproduced IL-6 in response to Gal-8. Finally, to confirm that IL-6 from antigenpresentingcells was mediating the Gal-8 costimulatory effect, splenocytes fromIL-6-deficient (IL6KO) or C57BL/6J (wild-type) mice pre-treated with Mitomycin-C, were co-cultured with purified CD4T cells from OTII mice in the presence ofOVA, Gal-8 or the combination of both. In agreement, Gal-8-inducedcostimulation of antigen-specific CD4T cell response was significantly impairedwhen APC from IL-6KO mice were used. Taken together, our results argue infavor of the participation of IL-6 in the immunostimulatory pathway induced byGal-8.