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The origin and stage of differentiation of the blast-crisis cells in chronic myelogenous leukemia have remained uncertain. Because immunoglobulin heavy-chain and light-chain genes must undergo a DNA rearrangement during B-cell development but rarely do so in human non-B-cell lineages, we examined these genes in 18 episodes of chronic myelogenous leukemia. In eight of nine episodes of lymphoid blast crisis, heavy-chain genes were rearranged, and in three, rearrangements in light-chain genes were also present. In contrast, cells from chronic myeloid, myeloid blast, and erythroid-like phases retained germ-like immunoglobulin genes. The observed phenotypic markers and gene configurations revealed that most lymphoid blast crises represent stages of development of B-cell precursors. In two separate episodes of lymphoid crisis, cells from a single patient possessed identical heavy-chain but different light-chain-gene configurations. Thus, the precursor cells that monoclonally expand to produce a lymphoid crisis are capable of immunoglobulin-gene rearrangements and represent discrete steps in early B-cell maturation.

The majority (80 per cent) of patients with acute lymphoblastic leukemia (ALL) have neither cell-surface immunoglobulin nor T-cell-associated surface antigens that would clearly identify the diseas...

Immunoglobulin genes in their germ-line form are separated DNA subsegments that must be joined by means of recombinations during B-cell development. Individual immunoglobulin-gene rearrangements are specific for a given B cell and its progeny. We show that the detection of such gene rearrangements by Southern hybridization provides a sensitive marker for both clonality and B-cell lineage within lymphoid tissues lacking expression of definitive surface phenotypes. We have used these genetic markers in three ways: to establish a diagnosis of lymphoma in a neoplastic disorder of uncertain cell type, to show that some lymphomas that were previously classified as being of T-cell type in fact contain monoclonal B cells, and to detect clonal B-cell populations within lymphomatous tissues of uncertain immunotype and within an atypical lymphofollicular hyperplasia having no other clonal surface markers. These sensitive and unique indicators of clonality located directly at the DNA level are capable of providing insights into the cellular origin, early detection, and natural history of neoplasia.