Fig. 1.

T cells compete for antigen-bearing DCs in vivo. (A) A total of 1 × 10⁷ P14.Thy1.1 spleen cells labeled with CFSE were transferred into C57BL/6 mice in the presence or absence of equal numbers of OT-I spleen cells. The next day, mice were immunized i.v. with various numbers of bone marrow-derived DCs pulsed with both ovalbumin and Y4A peptides. Spleen cells were analyzed 4 days after immunization. Histograms are gated on CD8, Thy1.1⁺, and class II MHC⁻ cells. The number of events is noted above histogram regions. (B) The number of P14 cells per spleen that had not divided or divided at least once was determined for multiple experiments performed as in A after immunizing with 2 × 10⁶ DCs. The number of P14 cells in the presence of OT-I cells was divided by the number in the absence of competitor. This ratio was averaged for four experiments for a total of 10 mice per group. (C) Experiment was performed as in A except that mice were immunized with 2 × 10⁶ DCs pulsed with both peptides (same DC) or two populations of DCs pulsed separately with each peptide (separate DC, 2 × 10⁶ each).