Fig. 4.

T cell competition occurs very early in the initiation of the response. (A) CFSE-labeled P14.Thy1.1 cells were injected with or without OT-I cells. Peptide-pulsed DCs and spleen cells were tested for expression of the activation markers CD69 and CD25 at 18 h. (B) Similar experiment to A except that results were averaged for mice with or without cotransfer of OT-I cells. (C) Cell transfer was performed as in other experiments except that OT-I cells were cotransferred simultaneously with P14.Thy1.1 cells or at the indicated times after immunization. n = 6–8, normalized results of two experiments. Statistical comparisons are shown. *, P < 0.01; **, P < 0.001.