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Long-term reconstitution of bursectomized chickens.


 Since the discovery of the immunologic role of the avian bursa of Fabricius (1), several investigations (2–4) have succeeded in defining functions of this organ. Bursectomy before hatching (5, 6), treatment of embryos or young chicks with testosterone (7) or cyclophosphamide (8), and bursectomy on the day of hatching coupled with whole body x-irradiation (9) block development of bursa-dependent components of peripheral lymphoid tissues.
 In later life, chickens bursectomized by one of these methods are deficient in immunoglobulins, lymphoid germinal centers, plasma cells and the ability to make antibodies. It can be concluded that the bursa of Fabricius is the central lymphoid organ in chickens, which performs crucial steps in the development of humoral immunologic competence.
 Less progress has been realized in attempts to define mechanisms of bursal action.