Gamma and delta chain gene rearrangement of T cell receptor in acute lymphoblastic leukemia

The immunophenotype, rearrangements of T cell receptor (TCR) gamma and delta chain genes as well as the immunoglobulin heavy chain (IgH) gene were studied in 37 cases of morphologically defined acute lymphoblastic leukemia (ALL). According to the expression of differentiation antigens, 8 cases were classified as T-ALL, 26 B lineage ALL, 2 acute undifferentiated leukemia (AUL) and myeloid phenotype. An order of TCR gene rearrangements was observed in T-ALL, with the rearrangement of delta gene preceding that of gamma gene. Both genes were also found frequently rearranged and/or deleted in high proportions of the ALL of B cell lineage. However, the patterns of gene rearrangements were somewhat different between the T and B lineage ALLs. In contrast, the IgH gene rearrangements were observed only in the B lineage ALL. The immunogenotype analysis of ALL proved to be a useful marker of the clonality and provided us with important information on early human lymphoid differentiation. We conclude that the determination of TCR gamma gene V-J junctional sequence can be used as clonal marker for detecting the minimal residual disease during clinical remission.