Figure 4: Increased hAb response to immunization in CB6F1 mice was dependent on memory CD4⁺ T cells.

CB6F1 mice (n = 5 per group per experiment) were intranasally exposed to A/CA (500 pfu/mouse) or PBS and then depleted of CD4⁺ T cells in between primary and secondary immunization using 500 μg Ab GK 1.5 given i.p., then allowed to reconstitute their naïve CD4⁺ T cell population prior to secondary i.m. exposure to rHA PR8 (1 μg/mouse) as shown in Supplementary Figure 3. Day 21 post rHA PR8 immunization A/PR8 HAI titer in panel (A), PR8 HA endpoint titer ± SD (Log₁₀) in panel (B). (*p<0.05, One-way ANOVA). Data shown are representative of two independent experiments (n = 5 mice per experiment).