T-cell immunology of the lung: maintaining the balance between host defence and immune pathology.

Respiratory immunology poses the dual questions of how to grapple with lung infection as one of the greatest unmet global health needs of our time, while also dealing with the growing challenge posed by chronic diseases of excessive or inappropriate lung inflammation and immunity, such as chronic obstructive lung disease and asthma. These separate branches of pulmonary research are linked by the clear observation that, in a tissue as fragile as the lung, protection from microbial attack may come at the cost of chronic inflammatory damage. A number of recent studies have considered specific aspects of this double-edged sword, including the diversity of responses to fungal exposure, sources and consequences of interleukin-17 immunity, and the role of tertiary lymphoid follicles in the lung.