T cell immunoglobulin and mucin domain 3 and its ligand galectin-9 are upregulated on activated monocytes during HIV infection.[31] Interaction between T cell immunoglobulin and mucin domain 3 and galectin-9 on monocytes may induce dysfunction, impairing their ability to regulate immune responses and contribute to the establishment of an immunosuppressive environment. This evidence concerns the gene LGALS9 and HIV infectious disease.