Changes in the titers of IgG antibodies against farmer's lung antigens in the sera of healthy dairy farmers.

We investigated the effects of exposure to biologic dust on IgG antibody levels of farmers during the indoor feeding season for cattle. The reference group consisted of 90 healthy, nonsmoking teachers. At the beginning of the indoor feeding season, the mean titer of IgG antibodies to A. umbrosus for the farmers was significantly higher than that for the teachers (P less than .001). During the indoor feeding season, the IgG antibody titer of A. umbrosus but not the titers of the other three studied microbes decreased for the farmers. For the teachers, titers of all four microbes decreased. The study confirmed earlier findings that, in Finland, exposure to A. umbrosus is related to cattle raising. The study also shows that during the indoor feeding season for cattle, the quality of hay and bedding materials is reflected in the serum antibody profile of even healthy dairy farmers.