Clonal evolution of lymphoblastoid cell lines.

Lymphoblastoid cell lines represent Epstein-Barr virus (EBV)-immortalized B lymphocytes, which are typically prepared by in vitro culture of normal blood cells. In this study, we evaluated the kinetics of clonal evolution in lymphoblastoid cell lines (LCLs) established from five different donors. Immunoglobulin heavy chain (IGH) and T-cell receptor gamma (TRG) gene rearrangements were tracked over time using PCR, while EBV clonality was tracked using Southern blot analysis of the viral terminal repeat fragment. All five cultures evolved towards monoclonal B cells within 8 weeks, while T lymphocytes disappeared over the same period. No significant association was found between the rapidity of clonal emergence and either the proliferation rate or the size of the EBV terminal repeat fragment, suggesting the random nature of clonal selection. Our results suggest that EBV-driven B lymphocytes rapidly progress from polyclonal to virtually monoclonal, which has implications for the pace at which lymphoma might evolve in vivo. In addition, our findings indicate that established lymphobastoid cell lines are not an ideal 'normal control' for human B lymphocytes because they do not represent the spectrum of polyclonal B cells found in healthy humans; instead, they primarily represent the progeny of a single B lymphocyte.