Adult T-cell leukemia (ATL) develops via multiple oncogenic steps in human T-cell leukemia virus type I (HTLV-I) carriers. To better understand pathogenesis of ATL, we developed a novel xenogeneic engraftment model in which primary ATL cells are intravenously transplanted into neonatal nonobese diabetic (NOD)/severe-combined immunodeficiency (SCID)/β2-microglobulinnull (NOD/SCID/β2mnull) mice. Acute-type ATL cells engrafted in the peripheral blood and in the lymph nodes of recipients at a high efficiency. Engrafted ATL cells were dually positive for human CD4 and CD25, and displayed patterns of HTLV-I integration identical to those of donors by Southern blot analysis. These cells infiltrated into recipients' liver, and formed nodular lesions, recapitulating the clinical feature of each patient. In contrast, in smoldering-type ATL cases, multiple clones of ATL cells engrafted efficiently in NOD/SCID/β2mnull mice. When smoldering-type ATL cells were retransplanted into secondary NOD/SCID/β2mnull recipients, single HTLV-I-infected clones became predominant, suggesting that clones with dominant proliferative activity can be competitively selected in this xenogeneic system. Taken together, the NOD/SCID/β2mnull newborn system is useful to understand kinetics, metastasis, and disease progression of ATL in vivo.
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