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Establishment of a human pro‐B cell line (JKB‐1) and its differentiation of preestablished bone marrow stromal cell layer

A human pro‐B cell line, named JKB‐1, was established from the bone marrow of a 16‐year‐old girl with acute lymphoblastic leukemia (ALL) in relapse. The origin of the JKB‐1 cell line was indicated by its chromosomal and immunologic similarity to the patient's fresh leukemic cells. This cell line has been growing for more than 14 months in suspension culture medium and had a doubling time of about 24 hours. JKB‐1 expressed terminal deoxynucleotide transferase (TdT) and early antigens (HLA‐DR, CD19, CD24) of B cells, with heavy chain gene rearrangement. However, it did not express late antigens (CD10, CD20, CD21, CD22, CD23) of B cells, light chain gene rearrangement, and cytoplasmic μ‐chain. These results suggested that JKB‐1 is at the stage of “pro‐B” cell or early B‐cell precursors.