Shedding light on cutaneous innate immune responses: the intravital microscopy approach

The skin is under constant assault by environmental factors and microbes. Innate immune cells in epidermis and dermis regulate immune responses against pathogens while maintaining tolerance against commensal bacteria and autoantigens. The introduction of intravital imaging approaches, in particular multiphoton microscopy, has enabled studying the cellular and molecular regulation of cutaneous immunity in real time within intact skin. Here, we discuss recent advances in our understanding of innate immune cell behaviour in the skin, as unravelled by intravital microscopy, with emphasis on the function of myeloid cells, including dendritic cells, neutrophils and monocytes.