DIFFERENTIAL GLYCOSYLATION OF T HELPER CELL SUBSETS SELECTIVELY REGULATES SUSCEPTIBILITY TO CELL DEATH

M. TOSCANO; G. BIANCO; J. ILARREGUI; L. CAMPAGNA; D. CROCI; G. RABINOVICH

RIO DE JANEIRO

Congreso; 13TH INTERNATIONAL CONGRESS OF IMMUNOLOGY; 2007

ICI 2007

Differential glycosylation of T helper cell subsets selectively regulates susceptibility to galectin-1-induced cell death   Marta A. Toscano, Germán A. Bianco, Juan M. Ilarregui, Leonardo Campagna, Diego Croci, Norberto Zwirner, & Gabriel A. Rabinovich1   1Division of Inmunogenetics, Hospital de Clínicas "José de San Martín", School of Medicine, University of Buenos Aires, Av. Córdoba 2351. 3rd Floor, C1120 Buenos Aires, Argentina   Galectin-1, a carbohydrate-binding protein found at sites of T-cell activation, has immunosuppressive effects in vivo. Administration of galectin-1 in experimental models of chronic inflammation and autoimmunity results in selective elimination of antigen-activated T cells and a T-helper (Th)1 to Th2 shift associated with remission of inflammatory disease. In addition, selective blockade of the inhibitory effects of galectin-1 within the tumor microenvironment results in heightened T-cell-mediated tumor rejection and increased survival of Th1 effector cells. The aim of the present study is to dissect the mechanisms involved in the galectin-1-mediated regulation of Th1 and Th2 responses. We demonstrate here that Th1- and Th2-promoting stimuli can differentially regulate the glycosylation pattern of human and murine T-helper cells and modulate their susceptibility to galectin-1. While Th1-differentiated cells express the repertoire of cell surface glycans that are critical for galectin-1 binding and cell death, Th2 cells are protected from galectin-1 through differential sialylation of N- and O-glycans on cell surface glycoproteins. Consistently, in vitro activation of galectin-1-deficient (gal-1-/-) CD4+ T cells results in enhanced Th1 cytokine secretion compared to wild type littermates [(IFN-g: 17±5.3 ng/ml vs. 3.2±1.3 ng/ml; P<0.05); (IL-2: 4.1±1.5 ng/ml vs. 1.9±0.2 ng/ml; P<0.05)]. Furthermore, gal-1-/- mice develop hyper-Th1 responses following specific antigenic challenge in vivo, characterized by significantly higher levels of IFN-g-producing cells (P<0.05) and enhanced T-bet expression compared to wild-type mice. Our findings identify a novel mechanism, based on differential glycosylation of Th1 and Th2 cell subsets, by which galectin-1 preferentially eliminates antigen-specific TH1-effector cells with critical implications for immunotherapy.