S3Ab, a novel antibody targeting B lymphocytes, is a potential therapeutic agent for B-lineage malignancies.

CD79α protein together with the related CD79β protein forms the B-cell antigen receptor (BCR). It remains present when B cells transform into active plasma cells, and is also present in virtually all B cell neoplasms. Monoclonal antibody (mAb) S3 (S3Ab) is a novel anti-CD79α antibody generated by using Raji cells as an immunogen. Herein, we conducted a study on S3Ab using various cellular and immunocytological techniques. The results showed that S3Ab could recognise CD79α in living cells. The molecular weights of the heavy and the light chains of S3Ab were 55 and 26 kDa, respectively. S3 antigen is only expressed on more mature B cells and negative on blast B cells. It could partially block the binding of anti-CD79α (Hm47, recognising the cytoplasmic domain of CD79α) to target cells. Immunoprecipitation experiment showed that S3 antigen is about 33 kDa and S3 can specifically bind to the recombinant extracellular segment of CD79α. The internalisation rate of S3Ab to the target cells was as high as 74.0% after incubation at for 3 h. In conclusion, S3Ab is probably a new target molecule for B cells and can be an excellent antibody in targeting treatment of haematopoietic malignancies, warranting further development of this agent.