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

我们对24例老年人（平均年龄79.3岁）的B淋巴细胞功能进行了评价。青年14例，平均24.5岁。人士当用金黄色葡萄球菌科万I刺激时，老年人的淋巴细胞与年轻人的淋巴细胞相比，掺入的氚化胸苷显著减少。此外，发现老年人自发分泌免疫球蛋白（IG）的细胞数量增加。然而，从老年人的淋巴细胞刺激美洲商陆有丝分裂原显示IG生产等于年轻人。老年人的结果与体内多克隆B细胞活化一致。15名青年（<50岁）接着研究它们产生趋化活性、吞噬活性和氧中间体的能力。来自老年供体的中性粒细胞产生的趋化活性低于来自年轻供体的中性粒细胞。相比之下，吞噬活性和生产的氧中间产物的中性粒细胞从年轻和老年捐助者是可比的。与衰老相关的中性粒细胞趋化性的选择性失败可能导致感染性疾病的发病率随年龄的增长而增加。由于肿瘤的发病率随年龄的增长而增加，因此可以预期老年人的NK活性受损。然而，在71至75岁，76至80岁和81至85岁的群体中，NK活性增加，尽管65至70岁和86岁以上的群体显示出与年轻人（18至50岁）相当的NK活性。观察到的NK活性的差异不能归因于老年人和年轻人血液中NK细胞百分比的差异。随着年龄的增长，NK活性的增加可能弥补了免疫功能的下降，以维持正常的免疫系统稳态。

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.