Current concepts on pulmonary host defense mechanisms in children

The respiratory tract is exposed continuously to noxious agents, microbial organisms, particles, and allergens. It has therefore evolved both innate a nd specific defense mechanisms. The innate host defense mechanisms include components such as collectins, beta-defensins, lactoferrin, and complement, all of which have an important role in modulating the immune response. Imm une protection of the lungs by specific antibody is reviewed. The airways a re protected by alveolar macrophages, neutrophils, and lymphocytes, and the ir origins, regulation, functions, and antimicrobial activity are summarize d. Antimicrobial peptides and immune-modulating peptides are likely to have a significant therapeutic role for infection and inflammation in the respi ratory tract. Curr Opin Pediatr 2000, 12:187-193 (C) 2000 Lippincott Willia ms & Wilkins, Inc.