ICOSLG was found in monocyte-derived dendritic cells, initial studies of ICOSLG focused on immune cells, its co-expression with ICOS can regulate the activation of CD4+ T cells (Wang et al., 2000; Wallin et al., 2001; Witsch et al., 2002).At present, with the expansion of research, ICOSLG has been confirmed to be associated with a variety of diseases, including immunodeficiency diseases (Dalakas, 2005), hematological diseases (Tamura et al., 2005). The gene discussed is ICOS; the disease is immunodeficiency disease.