Aging of the immune system.
A review of the literature shows that the thymus is the major reason for aging of the immune system. A graph of the mouse thymus mass is linear with age after puberty. However, T cell function is determined by thymic hormone factors and serum thymic factors. The net result is that T cell function is so affected that there is a deficit in T cell responsiveness. For humans a graph of 1-I (I is immunological efficiency) versus age is a straight line on a semi-log plot. The slope of the line is about the same as the incidence of class I cancer incidence vs. age.
D000375:Aging / Q000502:physiology*; D000818:Animals; D005260:Female; D006728:Hormones / Q000502:physiology; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000453:epidemiology / Q000276:immunology; D013950:Thymus Gland / Q000502:physiology*; D013951:Thymus Hormones / Q000502:physiology
D006728:Hormones; D013951:Thymus Hormones