Fig. 5.

Apyrase inhibits antibody responses induced by TIV adjuvanted with MF59, but not with alum and IFA. (A–C) Twelve mice per group were immunized as before with TIV and adjuvants, as indicated. The following doses were used: MF59 (40% vol/vol), IFA (40% vol/vol), alum (100 μg), apyrase (10 U per leg), and TIV (0.1 μg each antigen). (A and B) Serum samples were drawn 2 wk after the first (A) or second (B) immunization, and total IgG antibody titers toward H1N1/California were measured by ELISA. Values represent mean logarithmic titers (log 10) of eight to 12 mice per group + SD. (C) Spleens from 4 mice per group were taken 2 wk after the first immunization, and vaccine-specific CD4⁺ T helper cells were reactivated by in vitro stimulation. Their individual cytokine profile was assessed by intracellular cytokine staining and FACS analysis. The bars show cumulative numbers of vaccine-specific cytokine expressing cells, as indicated. Unpaired, two-tailed Student’s t test (T): *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.