IMMUNOGLOBULIN-V(H)4 GENE USAGE IN B-LYMPHOID LEUKEMIAS

V(H)4 gene rearrangements occur in a similar proportion of cases of B lineage acute lymphoblastic leukaemia (ALL) and B chronic lymphocytic leukaemia (B CLL). However, there may be differences in the pattern of V(H)4 gene usage between these disorders as is the case for V(H)1 gen e rearrangements. To examine this, we analysed the sequences of 24 PCR -amplified clonal V(H)4 gene rearrangements from a series of 15 cases of ALL and nine cases of CLL. Five distinct groups of genes were rearr anged, three of which (represented by V2-1, V71-2/V71-4, V4.21) have b een described in rearranged form in normal B lymphoid tissues. The mos t frequently rearranged gene was V4.21 which is strongly associated wi th autoimmune reactivity. V71-2, V71-4 and V2-1 were more frequently r earranged in CLL than ALL. The remaining two groups (represented by V4 .33, V4.35) have not previously been described in rearranged form. One of these, V4.35. was seen only in ALL rearrangements. Both V4.35 and a V(H)1 gene, 20P3, which is also preferentially rearranged in ALL, ar e located at the 3' end of the V(H) locus. The location of these genes suggests that their rearrangement may be developmentally regulated in ALL. The findings in this study confirm restricted repertoires of IgH gene rearrangement in ALL and CLL. Characterization of IgH repertoire s provides a means of correlating these transformed B cell populations with normal B cell developmental compartments. Moreover, the distinct ive repertoires in ALL and CLL may reflect important differences in th e ontogenic timing and microenvironmental milieu of tumourigenesis in these disorders.