Adoptive T cell transfer of CD4+ or CD8+ T cells provides challenge for protection, whilst sera shows no protection. (A) Naïve BALB/c mice were given memory splenocytes from vaccinated mice purified by magnetic selection (B) for total CD3+, CD4+ or CD8+ T cells. (A) Mice were given T cells i.v., and immune serum was given i.p. 500 μl on 4 separate days. Mice were then infected with 1LD50 H3N2, lung viral load determined at day 7 (C) (n = 3), and fold reduction in viral load compared to PBS negative controls (D), and monitored for survival to day 14 (E) (n = 5). Experiment was repeated twice. (C) Data represents the individual viral loads and group mean (n = 3), (D) data represents the average viral load reduction compared to PBS negative control mice, and (E) the % survival by day 14 post infection (n = 5).