Fig. 5.

Phenotype characterization of diphtheria, tetanus and pertussis (DTP)-specific CD4⁺ T cells in infants and adults. CD45RA^low cells were gated and a CCR7/CD27 combination was used to compare the phenotypes of pertussis toxoid (PT)-specific T helper type 1 (Th1) [interleukin (IL)-2 and interferon (IFN)-γ⁺] CD4⁺ T cells among infants and adults. Comparative dot-plots show frequencies of PT-specific IL-2⁺ and IFN-γ⁺ expressing CD4⁺ T cells among infants and adults (a). The bar graphs represent comparative percentages of PT-specific CD4⁺ T cells expressing IL-2 and IFN-γ based on their CCR7 and CD27 expression patterns (b). P-values were calculated using the Mann–Whitney U-test; *<0·05; **<0·005; ***<0·0005.