B Lymphocyte Antigen CD19
CD19 was first identified as biomarker of normal and neoplastic B lymphocytes as B4 antigen with the use of anti-B4 monoclonal antibody against CD19 (Anderson et al. 1984). Anti-B4 antibody in turn was encoded from cDNA clones of human tonsillar cDNA library, by selectively hybridizing with RNA from CD19+ cell lines. Both human and mouse CD19 molecules are highly homologous with a conserved cytoplasmic domain with no homology with other known proteins and an immunoglobulin-like extracellular domain, which gave CD19 molecule the status of a member of Ig superfamily (Tedder and Isaacs 1989).
The CD19 molecule is a 95 KDa cell surface protein of B lymphocytes and follicular dendritic cells (FDC). It is considered as a biomarker of B cell because of its continued expression throughout B cell differentiation stages starting from late pro-B cell stage until terminally differentiated plasma cells (Nadler et al. 1983;...