The formation and function of tertiary lymphoid follicles in chronic pulmonary inflammation.

Tertiary lymphoid follicles (TLFs) can develop in the respiratory tract in response to infections or chronic inflammation. However, their functional relevance remains unclear as they are implicated in both protective and pathologic responses. In contrast to homeostatic conditions, external antigens and damage to the lung tissue may drive TLF formation in inflamed lungs, and once established, the presence of pulmonary TLFs may signal the progression of chronic lung disease. This novel concept will be discussed in light of recent work in chronic obstructive pulmonary disease (COPD) and how changes in the pulmonary microbiota may be drive and direct TLF formation and function. We will also discuss the cellularity of TLFs at the pulmonary mucosa, with emphasis on the potential roles of LTi's, B and T cell aggregates and examine the function of key chemokines and cytokines including CXCL13 and IL-17, in the formation and maintenance of pulmonary TLFs. This article is protected by copyright. All rights reserved.