Figure 3. PspA peptide-specific IFN-γ secretion by CD4⁺ T cell following pneumococcal challenge.

Groups of 10 F1 (B6×Balb/c) mice were intranasally challenged with 10⁷ CFUs of S. pneumonia strain EF3030 in a 15 µl volume of Ringer's solution. Spleen and cervical lymph node (CLN) lymphocytes were isolated from mice, 28 days after intranasal challenge with Streptococcus pneumonia strain EF3030 (▪) and naïve (□). CD4⁺ T cells were incubated with 1 µM of PspA peptide (15 amino acid peptides that overlapped every 11 residues) plus mitomycin C-treated naïve syngeneic feeder cells, for 3 days, at a ratio of 5∶1×10⁶ cells. The results were expressed as the mean ± the standard error mean (SEM) of IFN-γ supernatant levels from 3 replicate determinations of three independent experiments. IFN-γ production of cultured supernatants was determined by Luminex capable of detecting >2 pg/ml of IFN-γ.