The Immune and Regenerative Response to Burn Injury

Abstract

Burn are diverse and complex injuries that not only have local effects but also serious systemic consequences through severe and prolonged inflammatory response. They are caused by heat, electricity, friction, chemicals, or radiation and are commonly divided into superficial, superficial partial-, deep partial- and full-thickness injuries. The severity of the burn depends mainly on the size and depth of the injury but also on location, age, and underlying systemic diseases. A prolonged and strong immune response makes major burns even worse by causing multiple systemic effects including damage to the heart, lungs, blood vessels, kidneys, and other organs. Burns that do not require surgical excision, superficial and superficial partial-thickness, follow the known progression of wound healing (inflammation, proliferation, remodeling), whilst deep partial- and full thickness injuries requiring excision and grafting do not. For these burns, intervention is required for optimal coverage, function, and cosmesis. Annually millions of people worldwide suffer from burns associated with high morbidity and mortality. Fortunately, over the past decades, burn care has significantly improved. The improvement in understanding the pathophysiology of burn injury and burn wound progression has led to developments in skin grafting, fluid resuscitation, infection control and nutrition This review article focuses on the immune and regenerative responses following burn injury. In the Introduction, we describe the epidemiology of burns and burn pathophysiology. The focus of the following chapter is on systemic responses to burn injury. Next, we define the immune response to burns introducing all the different cell types involved. Subsequently, we discuss the regenerative cell response to burns as well as some of the emerging novel treatments in the battle against burns.

Keywords: burn injury; immune response; inflammation; tissue regeneration.

Figure 1

(A) Burn depth. Burns are classified as superficial, partial thickness—superficial or deep, or full thickness. Superficial burns damage the different layers of skin, while deep burns damage soft (tissue fat and muscle) and even bone. (B) Jackson’s Zones. Burns consist of three distinguished zones of coagulation, stasis and hyperaemia. The zone of coagulation is the innermost zone, the primary site of the injury and once the burn occurs its cells will rapidly undergo necrosis. The surrounding zone of stasis is characterized by tissue damage and ischemia but may still be potentially salvageable. The outermost zone of hyperaemia will usually recover but is characterized by substantial local swelling and redness caused by the immediate inflammatory response to the injury. The innate immune system and its cells are the body’s first line of defense against invading pathogens following burn injury. Characterized by defense against pathogens and disposal of necrotic tissues, the innate immune response paves the way for the proliferative and remodeling phases of wound healing following a burn injury. The picture depicts local inflammatory response to superficial burn in the dermis.

Figure 2

Summary of the main immune and regenerative cells involved in burn wound healing at different stages of healing. Abbreviations: d, day; yr, year.