Establishment of an IL‐2 independent, human T‐cell line possessing only the p70 IL‐2 receptor

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Abstract
A continuous cell line was established from the blood of a patient (HH) with an aggressive cutaneous T‐cell leukemia/lymphoma who lacked antibodies to human T lymphotrophic virus, type 1. The immunophenotype of the cultured cells was CD2+, CD3+, CD4+, CD5+, CD8+, DR+ and CD25− (Tac, IL‐2 receptor α chain). Southern‐blot hybridization analysis of T‐cell‐receptor β chain DNA demonstrated the same rearrangement in freshly isolated blood cells and cultured cells, indicating that the cell line was derived from the patient's malignant clone. Since cultured T‐cells grew in complete medium without added IL‐2, we investigated whether HH cells could be producing and responding to IL‐2 in an autocrine fashion. However, no IL‐2 was detectable in supernatant from the cell line, while antibodies to IL‐2, or to the IL‐2 receptor α or β chains did not inhibit cell growth. In addition, no mRNA message for IL‐2 was detectable in these cells. The results appear to exclude an autocrine IL‐2‐dependent mechanism of cell growth for this T‐cell line. Although cultured HH cells lacked detectable IL‐2 receptor α chain, they did show increased proliferation to exogenous IL‐2. Binding studies with 125I‐IL‐2 demonstrated an intermediate affinity receptor for IL‐2, KD = 1.7nM, with 6400 binding sites per cell, suggesting the presence of an IL‐2 receptor β chain. Consistent with these findings 125I‐IL‐2 cross‐linking studies demonstrated a single receptor calculated to be 75kDa. Also, the β chain of the IL‐2 receptor was detected by immunofluorescence using specific monoclonal antibodies (MAbs). Nanomolar concentrations of an IL‐2‐diphteria toxin fusion protein inhibited cellular protein synthesis, an effect abrogated by native IL‐2. These findings indicate that the IL‐2 receptor β‐chain was functional. This novel mature T‐cell line may be useful in studies of IL‐2 receptor regulation and in analysis of the mechanism of T‐cell leukemogenesis.