Fig 2.

In vitro FIV infection of purified CD4⁺ CD25⁺ cells produces an activation phenotype. FACS-purified CD4⁺ CD25⁺ cells were either untreated, in vitro infected with FIV at an MOI of 2.5, treated with UV-inactivated virus, or in vitro activated by 4-day LPS and IL-2 stimulation. (A to C) Expression of GARP mRNA (A), cell surface protein (B), and mean fluorescence intensity (MFI) (C) was analyzed. CT, threshold cycle. (D) A representative flow cytometric dot plot showing GARP and FoxP3 expression in FIV-infected cells at 6 days p.i. with the percentage coexpressing GARP and FoxP3 in the upper right corner. (E to G) Expression of FoxP3 mRNA (E), intracellular FoxP3 protein (F), and MFI (G) was analyzed. GARP (C) or FoxP3 (G) detection by flow cytometry was also analyzed by MFI. (H) mTGF-β expression was assessed by flow cytometry; the percentage of cells expressing TGF-β is shown. n = 4 for each treatment group. *, P < 0.05 by Mann-Whitney test for significance. NS, not significant.