[Immunosenescence and the lung]

Ageing is accompanied by a series of structural and functional changes in the respiratory system, some of which depend on declining performance of the immune system.

The dominant risk for morbidity and mortality lies in respiratory infections with pneumococci and influenza virus. These risks are increased by immunosenescence, either intrinsic due to ageing or secondary to underlying diseases, poor diet, medication etc. Adaptive responses linked to memory are clearly degraded, particularly the naturally occurring or post vaccination responses to influenza virus antigens or polysaccharide antigens involved in the production of IgG sub class 2 antibodies. Alterations in innate responses have not yet been studied. The role of the immune system associated with the respiratory mucous membranes is reviewed. After the age of 50 several abnormalities develop in the lungs: reduced muco-ciliary clearance, loss of elastic fibres, and low grade inflammation that manifests itself as changes in broncho-alveolar lavage (neutrophilia, increased production of interleukin 8, elastase-antiprotease complexes). One also sees alterations in mononuclear cells with an increase in activated T lymphocytes. The defects of humoral immunity have, in part, been attributed to a functional deficiency of zinc. In the long term low dose replacement together with selenium reduce the frequency and severity of respiratory infections and some of the inadequate responses to vaccination.

The detection and treatment of immune deficiencies associated with ageing are becoming important therapeutic objectives; they may significantly improve the results and clinical benefits of vaccinations.

The declining performance of the immune system with age plays an important role in the development of lung diseases in the elderly.