Down-modulation of CD7 preferentially occurs in CD8 T cells in HIV-1 infection. The level of CD7 expression on CD4 and CD8 T cells in healthy individuals not infected with HIV (left panel). CD7 expression is preserved on CD4 T cells in patients with chronic HIV-1 infection (patient no. 1), whereas CD7 is partially down-regulated on CD4 T cells in patients with advanced HIV-1 disease (patient no. 2). Representative data are shown.