FIG. 4.

Representative results from a single-peptide screen demonstrate the diversity of the primary CD4 response to influenza virus HA. Mice were infected intranasally with A/New Caledonia/20/99 influenza virus, and the number of IL-2-producing CD4 splenocytes was determined 8 days later by 18-h in vitro stimulation with DAP.3-5.3.1 DR1-positive transfectants cultured with the single 18-mer peptides of interest at a 10 μM final concentration. IL-2 ELISPOT results quantified as the averages for duplicate wells with the background value (11 spots) subtracted are given. The results shown are representative of those of two to three independent experiments for each peptide. Spleen cells from six to seven mice were pooled for each experiment.