title: Absence of detectable IgM in enzymatically or biosynthetically labeled thymus-derived lymphocytes.
abstract: Surface proteins of mouse thymus and spleen cells were radioiodinated with lactoperoxidase. After solubilization, the labeled proteins were precipitated by antibodies directed against mouse immunoglobulin chains; the precipitates were analyzed by radioautography after Na dodecyl sulfate-gel electrophoresis. Radioactive mu and L chains were absent from thymocyte extracts and conspicuous in spleen-cell extracts. The following cells were biosynthetically labeled for 4 hr [(35)S]methionine or 24 hr with [(14)C]leucine: (1) Thymocytes, (2) cortisoneresistant thymocytes [both treated with rabbit antisera cytotoxic to bone marrow-derived (B) lymphocytes and IgM-containing plasma cells, to kill possible contaminating nonthymus-derived cells], (3) "activated thymocytes" (allogeneic cell cultures of cortisone-resistant thymocytes), (4) human Daudi cells (a B lymphoblastic cell line), and (5) purified mouse B spleen lymphocytes devoid of plasma cells. Again no mu and L chains could be detected in thymocyte or thymus-derived cell extracts by immune precipitation and gel electrophoresis, while these chains were conspicuous in B-cell extracts. "Educated thymocytes," obtained from spleens of lethally irradiated mice injected with syngeneic thymocytes and antigen, synthesized mu and L chains under similar conditions; this synthesis resulted from contamination of these cells by IgM-containing plasma cells.
mesh_terms: D000818:Animals; D001345:Autoradiography; D001402:B-Lymphocytes / Q000032:analysis; D002250:Carbon Radioisotopes; D002384:Catalysis; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007118:Immunoassay; D007075:Immunoglobulin M / Q000032:analysis*; D007457:Iodine Radioisotopes; D007553:Isotope Labeling; D007930:Leucine / Q000378:metabolism; D008214:Lymphocytes / Q000032:analysis / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D010544:Peroxidases; D011233:Precipitin Tests; D013154:Spleen / Q000166:cytology; D013462:Sulfur Radioisotopes; D013601:T-Lymphocytes / Q000032:analysis*
chemical_list: D002250:Carbon Radioisotopes; D007075:Immunoglobulin M; D007457:Iodine Radioisotopes; D013462:Sulfur Radioisotopes; D008715:Methionine; D010544:Peroxidases; D007930:Leucine