Definition of bursa of Fabricius in US English:

bursa of Fabricius


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

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


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.


bursa of Fabricius

/ˌbərsə əv fəˈbriSH(ē)əs/