[The bursa of Fabricius of chickens contains cells initiating the graft-versus-host reaction].

Allogeneic bursal fragments or bursal cells (B 14 or B 19), grafted on the chorioallantois, induce splenomegaly in the recipient embryo (B 14 or B 19). This splenomegaly compares to that instigated by spleen cells. Syngeneic bursal grafts do not result in spleen enlargement. The reaction is thus caused by the MHC difference of the two lines used. We conclude that B cells may have a role in initiating the GVH-R.