Who is really in control of skin immunity under physiological circumstances – lymphocytes, dendritic cells or keratinocytes?

Abstract

Our views of the skin immunity theatre are undergoing constant change. These not only reflect paradigm shifts in general immunology and skin biology, but also have profound clinical implications, which call for strategic changes in dermatological therapy. Nowhere can this be witnessed at a greater level of instructiveness and fascination than when addressing the question posed by this new Controversies feature. Thus, after a very long period of dominance by T cells and Langerhans cells as 'lead actors' on the skin immunity stage, the lowly keratinocyte has recently made an astounding theatrical appearance as a key protagonist of the innate skin immunity system, which may control even acquired skin immune responses. Further enhancing dramatic complexity and tension, the mast cell has entered as an additional actor claiming centre stage, and the epidermal Langerhans cell has slipped in a surprise appearance as the chief agent of immunotolerance. May you, esteemed reader, enjoy the spectacle offered here by selected immunodermatology authorities who double as 'stage managers' pushing their respective favourite actors into the limelight. You get everything you may expect from a good performance - complete with the impresario's overture that lures you into the theatre and sets the stage, competing divas, recently discovered new talents and even the critic's digest while the performance is still ongoing. By the time the curtain drops, you will have reached your own, independent conclusions on how to answer the title question of this play - at least for the time being...

Emerging Skin T-Cell Functions in Response to Environmental Insults

“…In addition, healthy human skin also harbors Foxp3 + memory regulatory T cells, termed mT REG cells, residing around hair follicles where they contribute to immune homeostasis, or if dysregulated can mediate immunopathology (Chow et al, 2013; Sanchez Rodriguez et al, 2014; Seneschal et al, 2012). The composition and function of cutaneous T cells can change dramatically on environmental insults and may be driven by both antigen exposure and innate immune signals derived from surrounding keratinocytes, dendritic cells, macrophages, and other cells (Iwasaki and Medzhitov, 2015; Schroder et al, 2006). This review article focuses on the effects of cutaneous T-cell activation in the context of environmental insults and the factors that maintain T cells in the skin to provide long-lived protective functions.…”

Applications of Nanotechnology in Dermatology

“…The skin provides both innate and adaptive immune response functions that maintain tissue homeostasis and the ability to react quickly to environmental insults (Iwasaki et al, 2004; Paus et al, 2006; Gallo and Nakatsuji, 2011). Almost every substance that contacts skin has the potential to penetrate and/or produce physiologic changes.…”

Alternative Methods of Vaccine Delivery: An Overview of Edible and Intradermal Vaccines

“…These cells are also efficiently stimulated by pathogen-associated molecular patterns (PAMPs) using an array of germline-encoded pattern recognition receptors (PRR), including toll-like receptors (TLR) and langerin (CD207) [100]. Importantly, skin resident mast cells are also key drivers of the innate immune response in the skin through the release of granules containing inflammatory mediators [102].…”