Production of interleukin-1 beta-like factor with synovial cell growth promoting activity from adult T-cell leukemia cells.

We observed a case of adult T-cell leukemia (ATL) with proliferative synovitis. Culture supernatants from ATL cells (ATL-SN) obtained from the peripheral blood constitutively produced an interleukin-1 (IL-1)-like factor in vitro, as shown by the growth inhibition factor (GIF) assay using the A375 melanoma cell line and the lymphocyte activating factor (LAF) assay using C3H/HeJ thymocytes. Neutralization studies indicated that polyclonal antibodies against IL-1 beta blocked most (80%) of the activity in ATL-SN. In addition, increased amounts of IL-1 beta mRNA were found in the ATL cells by dot blot analysis. Sephacryl S-200 chromatography showed that the molecular weight of this factor was approximately 17.5 kDa, and Western blot analysis revealed that this factor reacted with polyclonal anti-IL-1 beta antibody under the reduced condition. The isoelectric point was 7.5. Furthermore, ATL-SN showed significant activity in promoting the growth of synovial cells in parallel with IL-1 activity. These data suggest that the constitutive production of this IL-1 beta-like factor might be responsible for proliferative synovitis in this case.