Transfer of antibody against Borrelia duttonii from mother to young in ddY mice.

The route of transfer of anti-Borrelia duttonii antibody subclasses from mother to young and their role in protection against borrelial challenge infection in ddY mice were investigated. Offspring from infected and noninfected mice were segregated and nursed by noninfected or infected mothers. Enzyme-linked immunosorbent assay analysis of antibodies of the cross-suckled offspring revealed that anti-B. duttonii immunoglobulin G1 (IgG1) is transferred exclusively in milk and that IgG2a is transferred mainly in milk but also slightly through the yolk sac route. On the other hand, IgG3 is transferred mainly through the yolk sac route but also slightly in milk, whereas IgG2b is transferred through both routes but to a lesser extent. Anti-borrelial IgM was not detected in any offspring. The protective role of transferred IgG subclasses was examined by challenge infection with B. duttonii. Offspring from noninfected mice fed by infected mothers had IgG1, IgG2a, and IgG3 at challenge and were completely protected against the challenge infection. On the other hand, offspring from infected mice fed by noninfected mothers had only IgG3, and 8 of 10 were completely protected from challenge infection whereas the other 2 contracted slight and transient spirochetemia. These findings suggested that anti-borrelial IgG3 alone has considerable protective activity and that IgG1, IgG2a, or both, either by themselves or together with IgG3, have a complete protective activity against borrelial infection.