Lacrimal Gland NK Cells Are Developmentally and Functionally Similar to Conventional NK Cells

The murine lacrimal gland (LG), which produces crucial components of the ocular tear film, contains a population of natural killer (NK) cells. LG NK cells appear to belong to the conventional NK cell lineage, based on their cell surface receptor and transcription factor expression, absence in NFIL3 mice, and lack of RORγt expression during development. LG NK cells produce IFN-γ during the early stages of systemic murine cytomegalovirus (MCMV) infection. This effector response occurs in the absence of noticeable MCMV replication in the LG, indicating that LG NK cells are being activated by soluble factors. However, the magnitude of LG NK cell IFN-γ production during MCMV infection is significantly lower than spleen and liver NK cells. Adoptive transfer experiments in lymphopenic mice revealed that this hyporesponsive phenotype is tissue-specific, which indicates that that LG NK cells can produce a robust effector response.