Role of the Surface IgM-Inducing Factor in Development of B Lymphocytes in Chicken Embryonic Bursa of Fabricius

　The bursa of Fabricius plays essential roles in the establishment of immune functions of avian species as a primary site for differentiation and proliferation of B lymphocytes. The bursa of chick embryos is colonized by lymphoid cell precursors only between the days 7th of embryogenesis (E7) and E14. Susceptibility to the sIgM-inducing factor may fluctuate in bursal lymphoid cells during the lymphoid precursor cell-receptive period. In the present study, the dynamic changes in the sIgM-positive ratio and responsiveness to sIgM-inducing factor were examined in lymphoid cells sampled from the bursa during the B precursor cell-receptive period (E10 to E13) and findings suggest that responsiveness to sIgM-inducing factor varies with the development of the chick embryos. E11 is suggested to be a critical stage of B-lymphocytegenesis in the bursa of chick embryos.