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 I. The immunophenotype of the cultured cells was CD2+, CD3+, CD4+, CD5+, CD8-, DR+ and CD25- (Tac, IL-2 receptor alpha chain). Southern-blot hybridization analysis of T-cell-receptor beta 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 alpha or beta 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 alpha 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 = 1.7 nM, with 6400 binding sites per cell, suggesting the presence of an IL-2 receptor beta chain. Consistent with these findings 125I-IL-2 cross-linking studies demonstrated a single receptor calculated to be 75 kDa. Also, the beta chain of the IL-2 receptor was detected by immunofluorescence using specific monoclonal antibodies (MAbs). Nanomolar concentrations of an IL-2-diphtheria toxin fusion protein inhibited cellular protein synthesis, an effect abrogated by native IL-2. These findings indicate that the IL-2 receptor beta-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.
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