Terminal transferase-positive human bone marrow cells exhibit the antigenic phenotype of common acute lymphoblastic leukemia.

Combined immunologic assays for TdT enzyme and membrane markers show that TdT+ cells in nonleukemic human bone marrow carry ALL-associated and Ia-like antigens but no thymocyte markers or surface Ig. These cells could be precursors involved in acute lymphoblastic leukemia of the "common" or non-T, non-B type and in lymphoid blast crisis of Ph' positive chronic myeloid leukemia. A few TdT+, Ia+ cells express cytoplasmic IgM, indicating that some pre-B cells may be TdT positive.