Figure 1.

Exosomes preferentially enhance CTL proliferation stimulated by low-affinity peptides. Purified naive OT-I cells were labeled with CFSE and stimulated with peptides in the presence or absence of Exo. Peptides ranged from high affinity (peptide N4) to low affinity (peptide V4). (A) Representative CFSE dilution in OT-I cells stimulated for 2 days by peptides with diverse affinities presented by plate-bound recombinant MHC I (Dimer X). (B) Fold change caused by CTL-derived exosomes (Exo) in the cell number of OT-I cells compared to peptide-only controls. Comparisons were based on Student's t-test between T4 and each of other peptides. (C) Representative histograms. Black lines: peptide only. Red lines: peptide plus Exo. (ND: undivided cells; D1: cells divided once; D2: second division; D3: third division). (D) Effects of Exo on divisions of OT-I cells stimulated by different affinities. Data in (A,C) are representatives of at least 5 experiments. Asterisks indicate statistical significance. *P < 0.05; **P < 0.01; ***P < 0.001 by unpaired, two-tailed Student's t-test, which will be the same in the rest of this study.