Pre-B cells in |[kappa]|-transgenic mice

Recent experiments have shown that the microinjected κ-chain gene of transgenic mice is expressed in a tissue-specific fashion only in B lymphocytes1,2. The next step was to determine whether, within the B-lymphocyte lineage, the κ-chain gene was expressed in a normal developmental fashion. Normally, only μ heavy(H)-chain genes, and not κ-chain genes, are expressed in pre-B cells3. To obtain cloned cell lines derived from early cells of the B-cell lineage, we transformed bone marrow cells from κ-transgenic mice with Abelson murine leukaemia virus (A-MuLV) and tested the resultant cell lines for the retention of the κ transgene and its expression in RNA and protein. We found that cells with the pre-B phenotype exist in κ-transgenic mice. We further observed that in A-MuLV-transformed cell lines from a κ-transgenic mouse with a high copy number of the transgene, the proportion of cell lines expressing κ (transgenic κ) was higher than in cell lines from normal or low copy number transgenic mice.