Sites of Early B-Cell Differentiation Synthesis of Ab was shown to require the presence of an organ called the bursa of Fabricius(chickens) Cells that developed into mature Ab forming cells were called bursa-derived or B cells B cell differentiation (humans) Liver in early fetus During fetal development and throughout the rest of life switches to bone marrow Bone marrow is the primary lymphoid organ for B-cell differentiationSites of Early B-Cell Differentiation ◼ Synthesis of Ab was shown to require the presence of an organ called the bursa of Fabricius (chickens) ◼ Cells that developed into mature Ab forming cells were called bursa-derived or B cells ◼ B cell differentiation (humans) ◼ Liver in early fetus ◼ During fetal development and throughout the rest of life switches to bone marrow ◼ Bone marrow is the primary lymphoid organ for B-cell differentiation