IgA levels, bacterial carrier rate, and the development of bronchial asthma in children.
A total of 54 children, earlier hospitalized for asthma, were reinvestigated with regard to immunoglobulin formation in serum and saliva. Furthermore, the carrier rate of pathogenic bacteria in their throats was investigated, and in some of the children, who had their adenoids removed, immunofluorescent studies were performed. The study revealed highly reduced levels of serum and saliva IgA in the younger children with asthma. In addition, in these children a connection between recurring respiratory infections and high carrier rate of presumably pathogenic bacteria was observed. Also in the older children, significantly reduced levels of serum and saliva IgA compared with age related controls were found, but these children did not have an increased frequency of pathogenic bacteria or repiratory infections. In addition, low levels of serum IgM were found in the older children with asthma. The results of the study support the theory that low IgA levels facilitate the entrance of pathogenic bacteria through the epithelial surfaces, resulting in an overstimulation of the IgE system and the development of bronchial asthma in the younger children. In the younger as well as the older patients, a high frequency of atopy among the closest relatives was observed.