Presence of the original Vλ to Jλ coding joint and the new Vλ to Jλ rearrangement and quantification of the original λ chain transcript. PCRs were performed with primers that amplify the indicated VJ coding joint formation in the genomic DNA from HB4C5, HTD8, and its subclones. (A) A diagram of the PCR primers used to detect the VJ coding joint. The direction of primers used are indicated with arrowheads. (B) The PCR-amplified products were run on agarose gels and assayed for hybridization to a VλC5, Vλ4, and Vλ6 specific probes by Southern blotting. Bands corresponding to VJ coding joint for the original light chain λC5, Vλ4 joined to Jλ, and Vλ6 jointed to Jλ are shown (C) Expression of the original λ light chain and the μ heavy-chain mRNAs were examined by Northern blotting. Cells used as a source of mRNA are indicated above each lane.