Cell depletion increases neonatal antibody response to RSV infection. CD4, CD8, or NK cells were depleted during primary RSV infection of neonatal (A, B, F, and G) or adult (C and D) BALB/c mice or during secondary RSV infection of BALB/c mice initially infected as neonates (E). RSV-specific IgG was measured on day −1 (A, C, and F) or day 7 (B, D, E, and G) of RSV secondary infection. WT C57BL/6 mice were infected as neonates with RSV, with or without cell depletion (H) or compared with FasL−/− mice (I), and serum anti-RSV IgG measured on day 7 of RSV secondary infection. Points represent individual mice, lines represent mean of n ≥ 3 mice per group ± SEM (*P < 0.05, **P < 0.01, and ***P < 0.001, ANOVA and post-test). Data presented are pooled from two experiments except in C and D, which are from a single experiment.