**5. Conclusions**

BALT covers a large area in the lungs, from small irregular lymphocytes and DC clusters to B-cell follicles, germinal centers, FDCs, HEV lymphatics, well-developed dome epithelium, and highly organized lymphoid tissues. It has the potential to help researchers better understand the mechanisms underlying chronic lung diseases, particularly in mammals. The potential contributions of BALT at this point are the collection of antigens from the pulmonary airways, priming B- and T-cell responses, and aiding in the clearance of pulmonary diseases. BALT becomes a functional tissue due to the induction of T cells and the production of deep lymphoid tissue, which functions in priming immune responses in the lung, including IgA-secreting plasma cells. The development of effective vaccines, particularly in the prevention of viral infections, will be aided by lymphoid tissue production.
