Expression of the immunoglobulin C mu gene in mouse T and B lymphoid and myeloid cell lines

We have used cloned nucleotide sequences as probes to search for immunoglobulin RNA in T and B lymphoid and nonlymphoid tumor cell lines. Polyadenylated RNA from the cells was fractionated electrophoretically by size and fixed to diazobenzyloxymethyl-paper, and then immunoglobulin RNA species were revealed by hybridization with 32P-labeled cloned sequences for mu heavy chain and kappa light chain. kappa mRNA was detected only in B lymphoid lines known to synthesize kappa chains. No mu RNA was detectable in erythroleukemia, mastocytoma, or sarcoma cells. RNA bearing mu constant region (C mu) sequences, however, was detected in four of nine T lymphoma and four of five myeloid tumor cell lines tested, as well as in B lymphoma and "pre-B" Abelson lymphoma cells. In contrast to the single mu RNA species of 2.6 kilobases (kb) in a plasmacytoma, individual T lymphoma and myeloid lines yielded up to three discrete mu RNA species of apparent size 1.9, 2.2, and 3.0 kb, each different from the two mu RNA species in a B lymphoma line (2.4 and 2.7 kb) or the single species in "pre-B" lymphoma cells (2.9 kb). Both chromosomal complements of the C mu gene in STRij-4 T cells were found to be rearranged from their embryonic (germ line) context. The results suggest that the C mu gene functions not only in T cells, wherein the ability to recognize antigen is long established, but also in myeloid cells.