Cell volume control as a key regulator of immune cell function

As immune cells develop and migrate throughout the body, they encounter diverse biochemical, mechanical and osmotic environments. These environments can induce rapid changes in cell volume through the activation or inhibition of ion channels and transporters. Recent work has highlighted that volume regulation contributes to key aspects of immune-cell function, including migration, activation and proliferation. Focusing on neutrophils, macrophages, dendritic cells and T cells, the cell types for which the most direct experimental evidence is currently available, this review summarises our current understanding of the underlying mechanisms and examines the evidence linking changes in cell volume to immune-cell behaviour, including the extent to which such changes are passive consequences of environmental conditions or active regulators of immune-cell function. We also highlight the limited use of direct volume measurements and discuss how this constrains our current understanding, will review available approaches to measure cell volume, and outline key directions for future work.