Anti-bacterial IgA and IgG in mouse uterine luminal fluid, vaginal washings and serum

A previous study demonstrated that mouse uterine horns contained bacteria of several species on the morning after mating, and immunolabeling showed that many of these bacteria were coated with immunoglobulins. In the present study we used an ELISA technique to detect naturally-occurring antibodies against bacteria in mouse uterine luminal fluid, vaginal washings and serum. Each fluid contained specific IgA and/or IgG antibodies to five of the six bacterial species recovered from the uterus after mating. The uterine fluid antibodies that bound to the bacteria were mainly IgA molecules, while those in the serum were mainly IgG. Naturally-occurring bacterial antibodies in mouse uterine luminal fluid may play a role in protecting the endometrium against microbial infections.