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

CARABELLI, J; AOKI, MP; PRATO, CA; CAMPETELLA, O; SANMARCO, LM; TRIBULATTI, MV

Congreso; Reunión conjunta de Sociedades de Biociencias; 2017

Galectin-8 (Gal-8) is a mammalian lectin endowed with the ability  to  co-stimulate  the  antigen-specific  immune  response.  IL-6 is  a  pleiotropic  cytokine  that  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-8 costimulatory effect on antigen-specific CD4T cells. Firstly, we quantified IL-6 by ELISA in supernatants from DO11.10TCROVA mouse splenocyte cultures, stimulated with the cognate peptide OVA(OVA), Gal-8 or the  combination  of  both.  Notably,  IL-6  was  significantly  increased in  the  conditioned  media  from  Gal-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  assess  if  IL-6  is involved in Gal-8 costimulatory effect, splenocytes were stimulated, as before, but in the presence of an IL-6-neutralizing  monoclonal antibody or a matching isotype control, and T cell proliferation was determined. Interestingly, IL-6 neutralization specifically precluded Gal-8 costimulatory activity but did not affect antigen-specific T cell response. To identify those cells that produce IL-6 in 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+cells produced IL-6 in response to Gal-8. Finally, to confirm that IL-6 from antigen-presenting cells was mediating the Gal-8 costimulatory effect, splenocytes from IL-6-deficient (IL6KO) or C57BL/6J (wildtype) mice pre-treated with Mitomycin-C, were co-cultured with purified CD4T cells from OTII mice in the presence of OVA, Gal-8 or the combination of both. In agreement, Gal-8-induced costimulation of  antigen-specific  CD4T  cell  response  was  significantly  impaired when APC from IL-6KO mice were used. Taken together, our results argue in favor of the participation of IL-6 in the immunostimulatory pathway induced by Gal-8.