Fig 4.

Expression levels of MHC-I, MHC-II, CD40, and CD154 genes were determined by real-time quantitative PCR. Total RNA was extracted from the duck spleens. Duck GAPDH was used as an endogenous control. Total RNA from duck spleens after the injection of saline in adjuvant were used as a negative control. The expression levels are shown as the fold increase over those of the control groups. Control, negative control; 1, expression levels at day 7 after one immunization; 2, expression levels at day 7 after two immunizations. The error bars represent the means ± SD from six animals (n = 6). Asterisks (*) indicate significant differences compared to nonvaccinated controls (P < 0.05, Student's t test).