Chronic inflammation of upper airways in children: basic principles.

PROBLEMS/OBJECTIVES: A child's immune system has to initiate the immune response from scratch and cannot depend on a memory-type of immune response. Moreover, the immune system in newborns is also less efficient in inducing cytokine responses. In consequence, newborns and children are more susceptible to upper-airway infections and inflammation than adults. This manuscript summarises basic considerations relating to immune and inflammatory response in the upper airways and presents data about the processes involved in immunity development and maturation in children. METHOD: Literature review. RESULTS: Inflammation is a complex set of interactions between soluble factors and cells that can arise in any tissue in response to both exogenous (infectious, toxic...) and endogenous (auto-immune, ischaemia...) insults. It interacts actively with the adaptive immune response by launching the antigen processing and presenting phases. Reduced cytotoxic response during foetal life, poor T-lymphocyte response to mitogens, immaturity of T and B lymphocytes, inadequate cytokine synthesis, a marked deficiency of antibody production and reduced neutrophil, complement and natural killer activity are important contributors to the complex physiological deficiency of immunological function in neonates and young children. CONCLUSIONS: The importance of the control and self-limitation of the inflammatory reaction is demonstrated by observations that, in certain chronic infectious or inflammatory conditions, the inflammatory response causes more damage to the host than the microbe.