Tissue-resident innate immunity in the lung.

The lung is a unique organ that must protect against inhaled pathogens and toxins, without mounting a disproportionate response against harmless particulate matter and without compromising its vital function. Tissue-resident immune cells within the lung provide local immunity and protection from infection but are also responsible for causing disease when dysregulated. There is a growing appreciation of the importance of tissue-resident memory T cells to lung immunity, but non-recirculating, tissue-resident, innate immune cells also exist. These cells provide the first line of defence against pulmonary infection and are essential for co-ordinating the subsequent adaptive response. In this review, we discuss the main lung-resident innate immune subsets and their functions in common pulmonary diseases, such as influenza, bacterial pneumonia, asthma and inflammatory disorders.