CD3ζ reexpression in vitro is inhibited by an IL-2–blocking antibody. T cells from four asymptomatic HIV-infected donors (502, ◊; 503, X; 604, ▵; 605, □) cultured overnight with or without exogenous IL-2 (300 IU/mL) and/or anti–IL-2 blocking antibody 5334.21 (30 μg/mL). The percent of CD8 T cells staining above background for CD3ζ is shown. Statistically significant changes are indicated.