Bursal and postbursal cells in chicken. Occurrence of postbursal cells in bone marrow, thymus and spleen

摘要

AbstractTo study the postbursal nature of lymphoid cells found in the bone marrow, thymus and spleen, their capacity for a long‐term restoration of bursa‐dependent immune functions and of bursal and splenic morphology was evaluated using cyclophosphamide‐treated chicks as cell recipients. The results reveal that postbursal cells appear in significant numbers, first in the spleen and then in the bone marrow and thymus. This observation is interpreted to indicate that migration of postbursal cells from the bursa to bone marrow and thymus most probably occurs through the spleen. The findings also indicate that in the development of the B cell line an early postbursal cell and a mature postbursal cell can be distinguished. Both of these cell types are capable of further function without the influence of a bursal microenvironment. The mature postbursal cell does not have a capacity for formation of germinal centers in significant numbers in the spleen, but the early postbursal cell still shares this potential with its precursor, the bursal stem cell. They are also distinguishable by a slight proliferation of the early postbursal cells in the bursa when transferred into cyclophosphamide‐treated newly‐hatched recipients. Both of these cell types represent distinct entities in the stepwise development of the B