T cell receptor gamma chain variable gene rearrangements in acute lymphoblastic leukemias of T and B lineage.

The status of immunoglobulin and T cell receptor genes in acute lymphoblastic leukemia (ALL) of T and B lineage has been studied. Our data indicate that illegitimate gene rearrangements at immunoglobulin heavy chain (in T cell ALL), and T cell receptor beta chain (in pre-B ALL) genes are only rarely found (2 out of 30 patients). In contrast, T cell receptor gamma chain gene rearrangements, characteristically found in T-ALL, are also present in 7 of 18 patients with pre-B ALL. Several features distinguish these illegitimate T cell receptor gamma chain gene rearrangements from those in normal and leukemic T cells. V gamma genes located far upstream of the J gamma/C gamma complexes (V gamma 2, V gamma 3, V gamma 4, V gamma 5) appear to be preferentially used in normal adult peripheral blood T cells. In contrast, V gamma genes located immediately 5' to the J gamma/C gamma complexes (V gamma 8, V gamma 9, V gamma 10, V gamma 11) predominate in V gamma -J gamma recombinations observed in T-ALL and pre-B ALL. Whereas the J gamma 2 region is primarily used in T cell receptor gamma gene rearrangements observed in T-ALL, those in pre-B ALL are confined mostly to the J gamma 1 region. These data suggest a limited accessibility of the T cell receptor gamma chain gene locus for recombination processes in early stages of B cell differentiation.