Springer Online Journal Archives 1860-2000
Abstract Immunological reactions that occur in the respiratory tract in response to infectious agents have recently gained distinct attention. Humoral (1–20) and cellular immune reactions (16, 21–34) have been identified in the lungs of a number of animal species and of man. Respiratory tract infections occur frequently among the elderly and constitute one of the leading causes of death. Aged humans have a greater mortality from pneumonia (35), influenza (36), tuberculosis (37), infective endocarditis (38), urinary tract (39) and intraabdominal (40) infections. Perla and Marmorston reviewed the effects of aging on natural resistance to infection (41–42), and focused on four factors as major determinants of resistance in old age: (a) changes in structure and function of vital organs, especially endocrine glands and the splenic lymphatic apparatus; (b) underlying pathological conditions facilitating microbial invasion; (c) alterations in circulatory and nervous systems which lead to trophic changes and tissue anoxia; and (d) prolonged subclinical vitamin and mineral deficiencies. Some investigators have postulated that the predisposition of the aged to infections is not due to a declining immune response (42–43), rather than to other physiologic changes of aging. Many studies of animals and man have linked the increase of infectious disease in the aged to reduced immunological vigor (44–47), in particular, deficiency of T-cell dependent immune responses (reviewed in 48–51). These studies which focused on the circulating immune system (peripheral blood, spleen, and peripheral lymph nodes) while clearly important, have not included information on age-related changes in the mucosal immune system. Studies on mucosal immunity are obviously relevant for elucidating the mechanisms of infectious diseases in the elderly. The importance of such information is emphasized by accumulating evidence that microorganisms entering the host encounter a functionally compartmentalized and distinct lymphoid area underlying the mucosal surfaces of the lung, genital tract, and intestine. These distinct lymphoid areas are characterized by unique immune cell populations, cell trafficking and homing patterns, and immune responsiveness (reviewed in 48, 52–54). This critique will review and present work on local immune functions of the nasopharyngeal tract, with particular emphasis to the age-associated decline in resistance to infections. The meager data available in the literature wlll be organized in this review under humoral and cellular aspects of both animal and human studies.
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