Fig. 3. Cellular immune responses by the three vaccine antigen attachment ways. Splenocytes of immunised mice (n = 6) were stimulated with the antigen for 3 days. (A) Splenocyte proliferation assay was performed using a CCK-8 kit. (B–D) IFN-γ, IL-4 and IL-17 levels were detected through ELISA. The results are reported as the mean ± SD. *P < 0.05; **P < 0.01; ***P < 0.001.