Bronchus-associated lymphoid tissue (BALT) is not present in the normal adult lung but in different diseases

Bronchus-associated lymphoid tissue (BALT) was first described in the lungs of rabbits and differs greatly between species. It is part of the integrat ed mucosal immune system. This review clarifies its morphological definitio n and focuses on the situation in humans. The frequency of BALT at differen t ages, after chronic stimulation and in different diseases is described. I n healthy humans, BALT can only be found in the lungs of children and adole scents. The role of BALT in lung transplantation and in the development of low-grade malignant lymphomas in the airways is also discussed. furthermore , questions concerning the inducibility of BALT as an entry site for vaccin es, and the regulation of its activity for future therapeutic interventions in pulmonary immune reactions are addressed. Copyright (C) 2000 S. Karger AG, Basel.