Multilayered T-cell memory in human skin

The skin represents a highly complex immunological microenvironment capable of protecting the organism from infectious pathogens. Accordingly, the human skin harbors large quantities of immune cells, including billions of memory T cells (1,2). While some of these T cells are constantly recirculating through the skin and thus are in equilibrium with their counterparts in the blood, others remain permanently resident in the skin and never return to the circulation (2). A recent study published in Science Translational Medicine by Watanabe and colleagues (3) has shed new light on the composition of these recirculating and resident T-cell subsets in human skin, and has linked the malignant transformation of individual subsets to the variable clinical presentation of cutaneous T-cell lymphoma (CTCL).