SUMMARY
Natural Killer (NK) cells and innate lymphoid cells (ILC) type I (ILC1) are key effectors in host defense against
skin-borne viruses and in cutaneous anti-tumor responses; they also modulate inflammatory skin diseases.
Despite their critical role, little is known about the migratory patterns of skin-homing NK cells and ILC1, their
organ selectivity or functions, and whether they can be selectively targeted. In contrast, organ-selective homing
to skin and intestines of T cell subsets is harnessed for vaccine strategies and in the treatment of organ-specific
autoimmunity. This exploratory proposal is based on the overall hypothesis that there is a distinct population of
skin-homing NK cells and ILC1 that is is key to cutaneous host defense. To study skin-trafficking of NK cells and
ILC1, we propose to revisit the classic model of afferent lymph cannulation in the sheep, which allows to collect
NK cells during their physiological recirculation through skin. By targeted analysis of skin-recirculating lymph-
borne NK cells, we will assess expression of canonical skin-homing receptors and effector molecules. In addition,
we will use Cellular Indexing of Transcriptomes and Epitopes by sequencing (CITE Seq) to determine gene
expression profiles of skin-recirculating NK and ILC1 cells and assess overlap with NK cells in control sites
(intestinal lymph and blood). These studies will be complemented by genetic mouse models and viral skin
infection mouse models utilizing the poxviruses vaccinia virus (VACV) and ectromelia virus (ECTV). Our
preliminary studies discovered that skin-recirculating NK cells express high levels of a4ß1-integrin, whose ligand
VCAM-1 is constitutively expressed by skin vasculature. Therefore, we will test the role of a4ß1-integrin in NK
cell skin homing and relevance for resistance to skin-borne VACV and ECTV. This will also establish a pipeline
to test the significance of additional molecules expressed by skin-recirculating NK cell in future studies. In
summary, the proposed studies will greatly enhance our understanding of skin-homing NK cells and ILC1, and
our ability to manipulate skin-specific immune responses in cutaneous pathologies ranging from infection and
cancer to inflammation.