A novel method to bursectomize avian embryos and obtain quail----chick bursal chimeras. II. Immune response of bursectomized chicks and chimeras and post-natal rejection of the grafted quail bursas.

Two methods to bursectomize chick embryos before hemopoietic cell seeding of the bursa of Fabricius were compared in this work: section of the tail region at E3 including the presumptive bursal territory, and selective removal of the bursa at E5. Hatching ability is better with the former method, but survival rate and effectiveness of bursectomy are favored with the second, novel technique. Moreover, selective removal of the bursa at E5 can be followed by in situ engraftment of a quail bursa and construction of quail-chick bursal chimeras. The immune response of bursaless birds and bursal chimeras has been studied. Total absence of the bursa does not prevent a few B cells from differentiating and nonspecific Ig (IgM and/or IgG) from being secreted. As reported previously, bursaless birds, however, are unable to mount an immune response by producing specific antibodies. This immune function is restored by the graft of a quail bursa. The microenvironment of the bursa, although heterospecific, allows the expansion of the B cell population and generates the repertoire of the B cell antigen receptors. This process takes place during late embryonic and early postnatal life because the grafted quail bursal stroma is subjected to immune rejection from 2 to 3 wk after birth in all chimeras, which are, however, perfectly immunocompetent.