Modulation of synovial cell products by a factor from a human cell line: T lymphocyte induction of a mononuclear cell factor.

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Abstract
A human [lymphoma] cell line (U937) can be stimulated to produce a soluble factor (MCF [mononuclear cell factor]) by lectin-activated T lymphocytes or their soluble products. In prior studies, MCF produced by peripheral blood mononuclear cells can increase production of collagenase and prostaglandin E2 by adherent synovial cells obtained from enzymatically dispersed rheumatoid arthritis synovium. Peripheral blood T lymphocytes or cloned human T lymphocyte lines are apparently capable of inducing MCF production by the [neoplastic] monocyte-like U937 cells. MCF was demonstrated in the supernatant fluid from cocultures of U937 cells and T lymphocytes that were stimulated with phytohemagglutinin or concanavalin A for 24-48 h. The supernatant fluid from 24 h lectin-stimulated T lymphocytes was transferred onto the U937 cells and, subsequently, MCF activity was recovered for the U937 culture medium. The activity of the soluble T cell product on the U937 cells is time- and dose-dependent. A human cell line capable of MCF production in continuous culture was not previously available. The use of a monocyte-like cell line (U937) and cloned T lymphocytes now makes it possible to demonstrate the role of discrete cell populations in the production of MCF and other mediators.