Many Gal-9 receptors, including protein disulfide isomerase (PDI), TIM-3, IgM, IgE, CD40, CD44, and VISTA, are predominantly expressed within immune system cells, especially T cells and mediate various activities such as TCR and BCR signaling (IgM), adaptive Treg, Th17 and osteoblast differentiation (CD44), Th2 migration (PDI), HIV infection (TIM-3), and mitigating inflammation in asthma (IgE), etc. Gal-9/PDI interaction mediates Th2 migration through ECM and increases their vulnerability to HIV infection [108]. This evidence concerns the gene P4HB and HIV infectious disease.