I . Synthesis and Secretion of Immunoglobulins by Chicken Lymphoid Cells

In the chicken, the bursa of Fabricius is essential for the development of lymphoid cells that will synthesize and secrete both IgM and IgG (1-3). WheI1 newly hatched chickens are bursectomized and irradiated, they fail to synthesize serum immunoglobulin(s) (Ig) 1 even though the expression of cell-mediated immunity remains normal. Hence, the bursa of the chicken provides an excellent experimental model to study the development of the lymphoid cells which synthesize circulating Ig. The present report describes the synthesis and secretion of Ig by lymphoid cells obtained from the spleen, bursa, and thymus of the chicken. Both spleen and bursa cells synthesize IgM and IgG as defined by serology and acrylalnide gel electrophoresis. Kinetics of synthesis and secretion of Ig by normal spleen cells was not greatly different from that of mouse myeloma cells as previously reported (4). In addition to synthesizing and secreting IgG, the bursa cells synthesize IgM which apparently is not secreted. The structure of this IgM of the bursa cells was studied by acrylamide gel electrophoresis and found to be different from Ig synthesized by the lymphoid cells of the spleen which are differentiated from the bursa. Ig was not detected in thymus cells within the limits of the method used.