CTLA4 partially contributed to the acquisition of B7 in Jurkat (CD28 ^+/+ CTLA4 ^high ) cells, related to Fig. 3 . (A) FACS histograms showing the total and surface levels of CD28 and CTLA4 on Tregs and Jurkat (CD28^+/+CTLA4^high) cells, numbers on the left of histograms showing the MFI values. (B) Effects of CTLA4 and/or CD28 blockade on the abilities of Jurkat to acquire CD80 and CD86. Upper: Schematics of a Jurkat:Raji coculture assay examining Jurkat-mediated acquisition of B7 ligands from APCs. Lower: Representative FACS histograms showing the CD80-GFP or CD86-GFP levels on Jurkat (CD28^+/+CTLA4^high) cells after a 15-min incubation with either CD80^−/−CD86^−/−CD80-GFP⁺ or CD80^−/−CD86^−/−CD86-GFP⁺ Raji cells. Bar graphs on the immediate right show the normalized MFI values of acquired CD80-GFP or CD86-GFP on Jurkat cells, calculated by setting the MFI of “−, −, −, −” condition as 0 and the MFI of “+, +, −, −” condition as 100. Error bars are SD from three independent coculture experiments performed on three different days. *, P < 0.05; **, P < 0.01; ***, P < 0.001; unpaired two-tailed Student’s t test.