FIG. 1.

NP-specific CD8⁺ T cells expand and contract following LT-NP immunization. Groups of BALB/c mice were immunized i.p. with 30 pmol of LT-NP, 30 pmol of PA, or 30 pmol of LFn-NP_118-126 in the absence of PA or were not immunized. The frequencies of splenic NP-specific T cells on the indicated days after immunization were determined by (A) IFN-γ ELISPOT analysis or (B) flow cytometry using L^dNP tetramers. Data were compiled from several independent experiments, and the values are the results for 3 to 25 mice (A) and 7 to 10 mice (B). The dotted line indicates the limit of detection for the ELISPOT assay. (C) Expression of the T-cell activation marker CD44 on CD8⁺ L^dNP⁺ splenocytes isolated at the peak of the response to either LT-NP (day 6) or L. monocytogenes-NP (LM-NP) (day 7) or on naïve CD8⁺ cells from unimmunized mice.