AbstractThe phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) was used to examine the phenotypic changes in three African Burkitt's lymphoma cell lines, P3HR1, Daudi, and Raji. Cells were cultured with a nanogram concentration of TPA for up to seven days and then analyzed by flow cytometry and an immunoperoxidase staining method. The cells were stained with a panel of monoclonal antibodies reactive with B lymphocytes or B cell leukemia/lymphomas, and an antibody to the enzyme terminal deoxynucleotidyl transferase (Tdt). All three cell lines were found to express more HLA-linked DC/DS (Leu 10) antigen, while demonstrating a concomitant decrease in the expression of common acute lymphoblastic leukemia antigen (CALLA) and terminal deoxynucleotidyl transferase after TPA induction. The other antigens including Ig, BA1, BA2, Tac, Leu 8, Leu 1, C3bR, Leu 12, and Leu M5 showed no significant changes. The marker expression and differentiation pattern of these African Burkitt's lymphoma lines are very similar to those of pre-B cells except for the surface IgM expression observed in Daudi cells. The expression of CALLA and Tdt in African Burkitt's lymphoma is probably not the result of an Epstein-Barr virus infection, but may in fact reflect the true nature or origin of tumor cells. We conclude that African Burkitt's lymphoma cells are derived from an early stage of B-cell differentiation closely related to, but more mature than pre-B cells.