Immunology and skin in health and disease.

The skin is a complex organ that, in addition to providing a strong barrier against external insults, serves as an arena for a wide variety of inflammatory processes, including immunity against infections, tumor immunity, autoimmunity, and allergy. A variety of cells collaborate to mount functional immune responses, which are initiated by resident populations and evolve through the recruitment of additional cell populations to the skin. Inflammatory responses are quite diverse, resulting in a wide range of signs and symptoms that depend on the initiating signals, characteristics of the infiltrating cell populations, and cytokines that are produced (cytokines are secreted protein that allows for cell-cell communication; usually refers to communication between immune-immune cells or stromal-immune cells). In this work, we will review the skin architecture and resident and recruited cell populations and discuss how these populations contribute to inflammation using human diseases and treatments when possible to illustrate their importance within a clinical context.