Maturation of bursal stem cells within allogeneic or syngeneic bursal microenvironment: surface determinants and capacity for germinal centre formation.

Maturation of bursal stem cells in an allogeneic environment was studied. The occurrence of surface IgM, surface IgG, and Ia-like antigens on B cells after differentiatoin within an allogeneic bursa was studied. Furthermore, the immediate capacity of B cells to form germinal centres after differentiation in an allogeneic bursa was studied by injecting them with histocompatible T cells into "test-tube" birds. The results indicate that the switch to surface-IgG-bearing cells occurs in an allogeneic bursa in a similar manner as in a syngeneic bursa. Studies of the occurrence of Ia-like antigens on bursa cells demonstrate that they retain their original Ia-like antigens, even during maturation in an allogeneic host. Third, the results demonstrate that after differentiation within an allogeneic environment bursa cells have acquired the ijmediate capacity to cooperate with histocompatible T cells as measured by germinal centre formation in "test-tube" birds.