Does Foxp3+ T cell-mediated lung transplant tolerance depend on BALT formation?

Lung transplantation, while increasingly being offered to an expanding list of end-stage lung diseases, still suffers from poor long-term outcomes due to the development of allograft rejection. Regulatory Foxp3+ T cells have emerged as important modulators of lung transplant tolerance (1). Bronchus-associated lymphoid tissue (BALT), enriched in Foxp3+ T cells as well as B cells, develops following lung transplantation. While some studies have implicated BALT in the pro-inflammatory host response and allograft rejection, others have shown that BALT promotes tolerance, predominantly through the accumulation of Foxp3+ T cells (2, 3).