Divergent effects of Galectin-8 on the Immune System

MARÍA VIRGINIA TRIBULATTI, JUAN MUCCI, VALENTINA CATTANEO, ULF HELLMAN Y OSCAR CAMPETELLA

Río de Janeiro, Brasil.

Congreso; 13th International Congress of Immunology; 2007

Galectins are mammalian lectins that bind galactosyl residues. Galectin-8(Gal-8) is a tandem repeat-type galectin, presenting two carbohydrate binding-domains joined by a linker peptide. In contrast to Gal-1, 3 and 9, whose roles in the immune system were extensively studied, little is known about Gal-8 function. We have determined by RT-PCR and Western-blot the expression of Gal-8 in thymocytes, thymic epithelial cells and splenocytes then confirming our previous microarray data. In order to test for its biologic activity in the immune system, thymocytes and splenocytes were incubated with recombinant Gal-8. In thymocytes, apoptosis induction triggered by caspase-3 activation was observed, as assessed by substrate cleavage and flow cytometry. In contrast, Gal-8 induced proliferation in splenocytes as determined by 3H-thymidine incorporation. This effect was mainly due to T cells, however it was also observed in splenocytes from nude mice although to a lesser extent. Apoptosis and proliferation were fully prevented with TDG, a galactose analogue, demonstrating that these effects are due to the Gal-8 sugar-binding ability. In order to identify ligans in spleen, a MALDI-Tof approach was performed with binders eluted with lactose from a Gal-8 affinity chromatography column.