A 30-kDa protein is disulfide linked to IgM on normal and neoplastic murine B lymphocytes

Four cloned continuously cultured mouse B lymphoma cells of the lines WEHI-279, BCL1 and 38C-13 were used to study the surface presentation of IgM. Cells of all lines expose, in addition to mu 2L2, various, disulfide-linked subunits as already shown for normal B lymphocytes (Koch, N. and Haustein, D., Mol. Immunol. 1982. 19:477). In contrast to normal B cells, B lymphoma cells also carry IgM structures of higher molecular weight than mu 2L2 on their surface. Furthermore, B lymphoma cells of all investigated lines expose a mu 2L2 structure to which a 30-kDa protein is disulfide-linked. This 30-kDa protein could also be identified on normal mouse B lymphocytes when more drastic conditions were employed. mu 2L2 disulfide linked to this 30-kDa protein is the main IgM structure on normal and neoplastic B cells whereas only small amounts of mu 2L2 (unlinked to this protein) can be detected.