In contrast, Sudo et al.101 reported that germfree Balb/c mice exhibited significantly
higher levels of total IgE as well as OVA-specific IgE and IgG1 than conventional
mice 5 and 7 weeks after OVA feeding (5 mg/d for 4 d) followed by i.p.
immunization with 1 μg OVA in alum every 2 weeks. OVA-specific IgG2 levels were
comparable in the two groups. Oral tolerance induction in gnotobiotic (germ-free)
mice monoassociated with B. infantis at the neonatal stage was similar to that seen
in conventional mice, although their OVA-specific IgE levels were somewhat higher.
In contrast, colonization of mice with B. infantis at the age of 5 weeks resulted in significantly
higher OVA-specific IgE, and IgG1 and IgG2a concentrations after OVA
feeding before immunization, than compared to germfree animals.