Murine spontaneous T‐cell leukemia constitutively expressing IL‐2 receptor—a model for human T‐cell malignancies expressing IL‐2 receptor

We describe a new, spontaneously occurring BALB/c‐derived murine T‐cell leukemia. The leukemic cells, designated LB, grow rapidly and progressively in the syngeneic host with no signs of effective immunological resistance. LB cells expressed the Thy‐1⁺, Lyt‐2⁺, L3T4^‐, CD3^‐ class‐1⁺, CD25⁺ (IL‐2 receptor, IL‐2R), class‐II^‐, gp70^‐ phenotype. As LB cells express IL‐2, as indicated by staining with 2 distinct anti‐CD25 IL‐2R monoclonal antibodies (MAbs), the therapeutic efficacy of IL‐2‐diphtheria toxin‐related protein was tested on this leukemic model. IL‐2‐diphtheria toxin, but not diphtheria toxin, efficiently inhibited the proliferation of LB cells. The proliferation of a murine myeloma cell line, which does not express IL‐2R, was not inhibited by IL‐2‐diphtheria toxin. The possible implantation of this animal model in fundamental and practical studies is discussed.