Serum anti-ovalbumin (OVA) immunoglobulin E (IgE), IgG1, and IgG2a antibody responses in GF2-treated mice. BALB/c mice were immunized twice with 50 μg/mouse OVA adsorbed on 2 mg alum on days 0 and 10. To examine the effects of GF2, three groups of mice were additionally treated with different doses (1, 10 and 100 μg/mouse) of GF2 for 3 consecutive days (days − 1 to + 1 and days 9 to 11) simultaneously with each systemic immunization. Positive control mice received phosphate-buffered saline (PBS) instead of GF2. Subsequently, sensitized mice were given aerosolized OVA three times on days 14, 15 and 16. The negative control mice were neither sensitized with OVA nor given GF2 treatment. Blood was collected on the days indicated and serum levels of anti-OVA antibodies IgE, IgG1 and IgG2a were measured by enzyme-linked immunosorbent assay. Results are expressed as the mean ± SEM of five to eight mice per group. Experiments were repeated twice with similar results. *P<0·05; **P<0·01; and ***P<0·001 compared with the control group (OVA/PBS). #P<0·05; ##P<0·01; and ###P<0·001 compared with the OVA/GF2 (1 μg) group. †P< 0·05; ††P<0·01; and †††P<0·001 compared with the OVA/GF2 (10 μg) group. ‡‡‡P<0·001 compared with the OVA/GF2 (100 μg) group.