Effect of 3-hydroxyanthranilic acid in the immunosuppressive molecules indoleamine dioxygenase and HLA-G in macrophages

Indoleamine 2,3-dioxygenase (IDO) and human leukocyte antigen-G (HLA-G) are two molecules involved in immune tolerance. 3-Hydroxyanthranilic acid is an IDO downstream metabolite that can produce an important immune suppression. In dendritic cells, it induces HLA-G cell surface expression and secretion to the medium. The relationship between IDO and HLA-G seems to be dependent on the cell type. In this study we analyzed the effect of the tryptophan metabolite 3-hydroxyanthranilic acid in these two proteins in monocytes and macrophages. This compound decreased IDO activity while increased HLA-G surface expression in macrophages, but not in monocytes. Also, 3-hydroxyanthranilic acid decreased HLA-G1 shedding, but not HLA-G5 secretion by macrophages. These results stress the importance of 3-hydroxyanthranilic acid as a modulator of the immune response.