Characterization of acute lymphoblastic leukemia of childhood by immunoglobulin and T-cell receptor gene patterns

Molecular biological studies of immunoglobulin (Ig) and T-cell antigen receptor (TCR) genes provide novel approaches to the identification and characterization of the acute lymphoblastic leukemias (ALL). Such studies greatly enhance our understanding of both the cells of origin in these diseases and the order of assembly of immune receptor genes in B-cells and T-cells. The patterns of Ig and TCR genes in B-cell precursor and T-cell ALL of childhood and ALL of infancy are heterogeneous though generally distinctive. The vast majority of cases of B-cell precursor ALL of childhood rearrange Ig heavy (H) chain genes, and 40-50% rearrange Ig light (L) chain genes. In contrast, in ALL of infancy, Ig genes are frequently germline, indicating generally less mature cells of origin in younger patients. Similarly, the vast majority of cases of T-cell ALL of childhood rearrange TCR delta, gamma, and beta genes and approximately one-half rearrange TCR alpha. TCR gene rearrangements are very common in cases of B-cell precursor ALL, but in patterns different from T-cells. In contrast, T ALL cells only infrequently rearrange Ig genes, and TCR gamma rearrangements are not found in ALL of infancy. The demonstration of lineage non-restricted Ig and TCR gene rearrangements raises questions about lymphocyte development and about the 'precursor' nature of ALL. The identification of generally distinctive patterns of these genes creates a foundation for their utilization as markers of minimal and preclinical disease. The extent to which specific immune receptor gene patterns correlate with clinical outcome in ALL warrants further study.