Spontaneous production of an interleukin 1-like factor by cloned rheumatoid synovial cells in long-term culture.

We have cloned adherent synovial cells from rheumatoid synovitis. These can be generally divided into three types, including cells that have the characteristic features of dendritic cells (DCs), macrophagelike cells (MCs) and fibroblastlike cells (FCs), as classified by morphology and immunofluorescent staining. The cloned cells were able to divide and were cultured for up to 11 mo without any significant morphological changes. All the cloned cells were HLA-DR+ after gamma-interferon treatment. Spontaneous production of a factor with interleukin 1 activity by the cloned cells was detected even after long-term culture (the ability, on a per cell basis, being in the following order: DC greater than MC greater than FC). These synovial cells may be important for bony destruction in rheumatoid joints.