Nature of the decline in antigen-induced humoral immunity with age

An attempt has been made to summarize our present knowledge of the influence of age on humoral immunity, as judged by the ability of an individual to generate antibody in response to antigenic stimulation. In general, humoral immunity declines with age, and the onset can occur as early as when an individual reaches sexual maturity. The decline is due to changes in the immune cells and their milieu. Cell loss, shift in the proportion of subpopulations, and qualitative cellular changes have all been detected. The most prominent cellular target of aging appears to be T cells involved in the regulation of humoral response. Since the changes are closely associated with the involution and atrophy of the thymus, an understanding of its changes could be the key to understanding immunosenescence.