Protein expression of alternative transcripts of CD79.

(A) The results obtained when the alternative transcripts of CD79 were cloned into pcDNA3 and translated into protein using a coupled transcription translation system (see “Materials and methods”). Proteins were resolved on a 15% SDS-PAGE gel and detected by fluorography. The positive control used was a vector coding for the luciferase protein. (B) An ELISA using a panel of anti-CD79b mAbs was used to assess binding to the full-length (full-CD79b-Fcγ) or alternately spliced (ΔCD79-Fcγ) extracellular domain of CD79b. (C) COS-7 cells were transiently transfected with full-length or truncated CD79b and then harvested 24 to 48 hours later for blotting with different anti-CD79b mAbs and detection with ECL reagents. All mAbs show specific reactivity with both the full and truncated forms of CD79b, shown as bands of 33 and 17.5 kDa, respectively. “Vector” indicates cells transfected with empty pcDNA3 plasmid, and “M” indicates the molecular weight markers. (D) Expression of ΔCD79b in Raji, Daudi, and EHRB B-cell lines and the EHRB transfectant clones 9 and 12 detailed in Figure 2. Expression was determined following Western blotting with anti-CD79b mAb AT105/1.