The response of rat bronchus-associated lymphoid tissue to local antigenic challenge.

Single doses of antigen suspension (alum-precipitated canine serum proteins) were administered intratracheally to SPF rats. After periods of 1, 2 and 3 weeks rats were killed and their lungs examined histologically. After an initial macrophage and perivascular lymphoid reaction, dose-related increases were found in the amount of bronchus-associated lymphoid tissue (BALT) and in the amount of DNA within BALT cells, indicating increased cell division. Immunoglobulin-containing cells were demonstrated within BALT 3 weeks after the exposure to antigen. A prominent and extensive bronchial lympho-epithelium was seen overlying BALT follicles in antigen-treated rats, while in control animals the respiratory epithelium overlying BALT was predominantly normal ciliated epithelium. The significance of these findings is discussed in the light of the possible defensive role of BALT in cases of respiratory disease of man and animals.