sdAb19 reverses Nef effects on peripheral CD4⁺ T cells in vivo. Peripheral lymph nodes were analyzed 4-5 months after reconstitution, gating on donor (CD45.1⁺) cells. Gating of GFP⁻, GFP^hi, and GFP^low cells was based on distribution of cell populations with distinct GFP intensities as well as levels of CD4 in Tg sdAb19⁺ chimeras. (A) Average CD4 MFI on pLN CD4⁺ T cells was compared with the average CD4 MFI found on CD4⁺ T cells in non-Tg chimeras. CD4 MFI in Tg GFP⁻ cells was determined on CD4^low cells. (B) Average percentage of cells expressing CD44 or CD25 among pLN CD4⁺ T cells showing CD4 and GFP high or low levels or among CD4^low T cells in chimeras reconstituted with uninfected Tg fetal liver. (C) Percentage of GFP^hi and GFP^low cells within designated subsets. Statistical analysis was performed with the Student t test (*P < .5, **P < .01, and ***P < .001; ns indicates not significant). Error bars represent 1 SD from the mean.