REARRANGEMENT OF THE IMMUNOGLOBULIN HEAVY-CHAIN GENE IN JUVENILE CHRONIC MYELOID-LEUKEMIA

Five patients with clinical and laboratory features typical for juveni le chronic myeloid leukaemia (JCML) are presented, Rearrangement of th e j joining region of the immunoglobulin heavy chain (Jh) was demonstr ated in three children out of five analysed. As no Vh to DhJh nor kapp a light chain rearrangements were demonstrated, it is reasonable to sp eculate that the transforming event of the stem cell happened at the s tage when Dh to Th rearrangement took place. As the monocytic lineage is prominent in JCML, it is suggested that the transforming event happ ens in a unique stem cell with intermediate differentiation towards th e myelomonocytic as well as the B-lymphatic lineage. This stem cell, w hich is present at a certain stage of embryogenesis, disappears later. Such an early 'hybrid' cell is sometimes involved in leukaemias of ea rly infancy, and may be the transformed cell in some cases of infantil e leukaemia.