Figure 3. The extrinsic acquisition of CD80 by CD8⁺ T cells occurs only in the lymphoid organs but not in the blood and LG. (A) Experimental scheme for analyzing the location of extrinsic acquisition of CD80 by CD8⁺ T cells. Either WT P14 CD8⁺ or CD80-KO P14 CD8⁺ T cells were adoptively transferred into WT recipient mice. One day after the adoptive transfer, mice were intraperitoneally infected with 2×10⁵ PFUs LCMV Arm. (B) Expression of CD80 among donor WT and CD80-KO P14 CD8⁺ T cells obtained from PBMC and various tissues in WT recipient mice at the days indicated post-infection. (C and D) Frequency of CD80-expressing cells (C) and MFI of CD80 (D) among WT or CD80-KO P14 CD8⁺ T cells obtained from PBMC, LG, LN, and SP in WT recipient mice at the days indicated post-infection. (E) Expression of CD80 among donor WT and CD80-KO P14 CD8⁺ T cells obtained from the SP of WT mice at day 80 post-infection. (F) Frequency of CD80-expressing cells and MFI of CD80 among WT or CD80-KO P14 CD8⁺ T cells obtained from the SP of WT mice at day 80 post-infection. Data are representative of 3 independent experiments (n=3−4 mice per group). Results represent mean±SEM and statistical significance was determined by 2-tailed unpaired Student's t-test.

NS, not significant; MFI, mean fluorescence intensity.

^*p<0.05; ^**p<0.01; ^***p<0.001.