Figure 4
Effects of EE caging on primary and secondary vaccine responses and spleen composition. (A) Influenza vaccine-specific IgG titers were measured in serum from mice vaccinated once (prime) or twice (boost) using an ELISA. In primed groups, EE mice had slightly lower IgG titers than control-caged mice (p = 0.0943), whereas in boosted groups, EE mice had slightly higher IgG titers than controls (p = 0.1950), although neither difference was statistically significant. Control mice exhibited an increase in IgG titer, from prime to boost, of 11.4%, whereas EE mice exhibited an increase of 23.8% (control, p = 0.0138; EE, p = 0.0006). (B) 1 × 106 splenocytes were stimulated with either PBS or vaccine for 24 h in an IL-5 ELISPOT assay. Primed animals showed no difference between caging groups, whereas splenocytes from boosted EE mice that were stimulated with vaccine had a significantly greater frequency of IL-5-secreting cells than boosted controls (p = 0.0493). The increase in frequency of IL-5-secreting cells from prime to boost was larger in EE mice (334.2%) than controls (177.9%) (control, p = 0.0230; EE, p = 0.0005). (C) A nonsignificant negative trend was observed between IL-5 production and mean FCM concentration (r2 = 0. 38, p = 0.0781). (D) Spleen mass per unit body mass was found to be significantly lower in boosted control-caged mice than boosted EE-caged mice (p = 0.0001). (E) A negative relationship was observed between mean FCM concentration and spleen mass per unit body mass in vaccine-boosted animals (r2 = 0.90, p < 0.0001). (F, G) Negative relationships were also observed between mean FCM concentration and CD19+ B cell number and CD4−CD8− lymphocyte number (CD19+, r2 = 0.39, p = 0.0533; CD4−CD8−, r2 = 0.52, p = 0.0190). Data are mean ± SEM. *p < 0.05, ***p < 0.001.