The thymus at thirty.
D000367:Age Factors; D000818:Animals; D006801:Humans; D007107:Immune System / Q000502:physiology*; D008214:Lymphocytes / Q000276:immunology; D051379:Mice; D013934:Thymectomy; D013950:Thymus Gland / Q000276:immunology* / Q000601:surgery