Interleukin‐2 Receptor β‐Chain (p70–75) Expressed on Leukemic Cells from Adult T Cell Leukemia Patients

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Abstract
To determine whether the interleukin-2 receptor (IL-2R) .beta.-chain (p70-75) is expressed on leukemic cells from patients with adult T cell leukemia (ATL) as well as .alpha.-chain (p55, Tac), we performed radiolabeled interleukin-2 (IL-2) binding assay, chemical crosslinking of radiolabeled IL-2 and flow cytometric analysis using a newly-developed anti-IL-2R .beta.-chain antibody. The results showed that leukemic cells from all the 12 ATL patients we examined expressed the IL-2R .beta.-chain together with the .alpha.-chain, whereas there was no detectable .beta.-chain expression on unstimulated peripheral blood CD4(+) T cells from healthy volunteers. Southern blot analysis revealed that this abnormal expression was not caused by the structural change of IL-2R .beta.-chain gene. Though leukemic cells from all ATL patients examined expressed high-affinity IL-2Rs, leukemic cells from only 25% of all ATL patients proliferated in response to IL-2. These results showing abnormal expression of IL-2R .beta.-chain on leukemic cells from ATL patients (ATL cells) suggest a close association between HTLV-I infection and abnormal .beta.-chain expression as well as .alpha.-chain expression.