Our results also found that in OSCC, the high expression of ICOSLG in TCs led to a decrease in CD4+ T cells in the tumor front and center and peripheral blood, while the proportion of Foxp3+ cells in the tumor infiltration front showed an increasing trend, indicating that the high expression of ICOSLG is likely to be involved in the occurrence of immunosuppression in the tumor microenvironment. The gene discussed is CD4; the disease is neoplasm.