Definition of bursa of Fabricius in English:

bursa of Fabricius


  • A glandular sac opening into the cloaca of a bird, producing B-cells.

    • ‘These drugs prevent development of the bursa of Fabricius and so selectively reduce humoral immunocompetence without influencing macrophages or cell-mediated immunity.’
    • ‘In birds, the thymus and bursa of Fabricius are the sites of maturation of T and B lymphocytes, respectively.’
    • ‘Birds that possessed a bursa of Fabricius were classified as young birds in their second or third calendar year.’
    • ‘Males with large badges have a smaller bursa of Fabricius than do average males.’
    • ‘Measurements of immunological structure include peripheral white blood cell counts and the mass and cellularity of immune organs such as the thymus, spleen, and bursa of Fabricius.’


Mid 19th century (in the Latin form bursa Fabricii): from bursa and a Latinized form of the name of Girolama Fabrici (1533–1619), Italian anatomist.