Critical role of keratinocytes in cutaneous immune responses

Keratinocytes play an integral role in the human epidermis, serving as a barrier between the internal and external environment. They are immune-competent cells involved in both innate and adaptive cutaneous immune responses, crucial for maintaining skin integrity. Keratinocytes are essential for epidermal repair, facilitating proliferation and re-epithelialization following injury. They secrete pro-inflammatory markers such as cytokines and chemokines, which promote the recruitment of inflammatory cells like polymorphs and macrophages to the site of skin injury. The immune response mediated by keratinocytes involves signaling molecules like tumor necrosis factor (TNF), interleukin (IL)-1β, and IL-6. Langerhans cells respond to factors secreted by keratinocytes, migrating towards draining lymph nodes to activate T cells and initiate an adaptive immune response. Additionally, keratinocytes express Toll-like receptors (TLRs), enabling them to detect molecular patterns of pathogens. Recent studies have focused on understanding these interactions of keratinocytes to develop therapeutic strategies for managing various skin diseases. Genetic defects in keratinocytes underlie conditions like psoriasis. We also discuss the role of keratinocytes and the effect of neuro-endocrinal signaling and interventions, associated corticosteroidogenic pathways, and response to UV radiations to maintain a state of homeostasis. This article underlines and improves our understanding of the immune function of keratinocytes, which is crucial for developing more effective therapies against skin diseases.