Immunology and aging.
D000375:Aging; D000818:Animals; D006801:Humans; D008208:Lymphatic System / Q000502:physiology*; D008214:Lymphocytes / Q000502:physiology; D051379:Mice; D009424:Nervous System Physiological Phenomena; D051381:Rats; D013950:Thymus Gland / Q000502:physiology