Production of Bone-resorbing Activity Corresponding to Interleukin-1α by Adult T-Cell Leukemia Cells in Humans¹

The physicochemical properties and relationship of bone-resorbing activity and interleukin 1 (IL-1) produced by adult T-cell leukemia (ATL) cells and cell line were studied in vitro. The culture supernatant of ATL cell line, MT2, and peripheral blood lymphocytes freshly obtained from ATL patients had both IL-1 activity detected by the stimulation of murine thymocyte-proliferative responses and bone-resorbing activity detected by the stimulation of ⁴⁵Ca release from prelabeled murine fetal bones. By Sephacryl S-200 column chromatography, both activities were eluted as a single peak at approximately M_r 15,000. By the chromatofocusing technique, the isoelectric point values of both activities were estimated as pH 4.8 and 5.2. Furthermore, both activities were absorbed with rabbit anti-IL-1α antiserum, but not with anti-IL-1β antiserum. These results suggest that ATL cells and cell line produce bone-resorbing activity which corresponds to IL-1α and that this IL-1α is one of the most important causes of hypercalcemia in ATL patients.