Immunoglobulin gene rearrangement in immature B cells

Two types of immature B cells, namely fetal liver hybridomas and the leukemic cell line 70Z/3, both of which have cytoplasmic mu chains but no light chains, were examined for DNA rearrangements of their light chain and heavy chain immunoglobulin genes. In the fetal liver hybridomas, which were constructed from fetal liver cells and a tumor cell, no light chain gene rearrangement was observed, whereas in the 70Z/3 cell line a kappa light chain rearrangement probably occurred. The results suggest that, although the lack of light chain synthesis can be due to a lack of gene rearrangement, there may also be transcriptional regulation, which may also be important for the expression of light chain immunoglobulins in immature B cells.