Age-related alteration of immune functions in humans and its relation to autoimmunity

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We evaluated B lymphocyte function in 24 elderly (mean 79.3 yr.) and 14 young (mean 24.5 yr.) persons. Lymphocytes from elderly persons incorporated significantly less tritiated thymidine as compared with lymphocytes from young persons when stimulated with Staphylococcus aureus Cowan I. Moreover, the elderly persons were found to have elevated numbers of cells spontaneously secreting immunoglobulin (Ig). However, lymphocytes from elderly persons stimulated with pokeweed mitogen displayed Ig production equal to young persons. The results in elderly persons are consistent with polyclonal B cell activation in vivo.Neutrophils from 25 elderly persons (70 to 80 yr.) and from 15 young persons (<50 yr.) were next investigated for their ability to produce chemotactic activity, phagocytic activity and oxygen intermediates. Neutrophils from old donors produced less chemotactic activity than did neutrophils from young donors. In contrast, phagocytic activity and production of oxygen intermediates by neutrophils from young and old donors were comparable. The selective failure in the chemotaxis of neutrophils associated with aging could contribute to the increase with age in the incidence of infectious diseases.Because of the increase with age in the incidence of neoplasia, one can expect impaired NK activity in aged humans. However, increase in NK activity was demonstrated in groups aged 71 to 75, 76 to 80 and 81 to 85, although groups of 65 to 70 years and more than 86 years showed a comparable NK activity to that in young persons (18 to 50 years). The difference in observed NK activity could not be attributed to differences in percentage of NK cells in the blood from old and young persons. Increase with age in the NK activity may make up the decline of immunologic competence with age for maintaining normal immune system homeostasis.