IFNLR1 and viral infectious disease: However, recent findings challenge the view that IFN-λ is primarily an epithelial cytokine, describe IFN-λ’s ability to directly and indirectly modulate immune cell functions and document the expression of IFNLR1 on immune cells; they also document that among immune cells, neutrophils express IFNLR1 and directly respond to IFN-λ, in the setting of viral infections (19) as well as other forms of acute inflammation (20–22).