helper T cell CD4-positive type I NK T cell activated CD4-positive type I NK T cell A type I NK T cell that has been recently activated, secretes interferon-gamma and IL-4, and has the phenotype CD4-positive, CD69-positive, and downregulated NK markers. activated CD4-positive type I NK T lymphocyte activated CD4-positive type I NK T-cell activated CD4-positive type I NK T-lymphocyte activated CD4-positive type I NKT cell cell