Interactions of T helper cells with fibroblast-like synoviocytes: up-regulation of matrix metalloproteinases by macrophage migration inhibitory factor from both Th1 and Th2 cells.

Objective: Interactions of immune cells, such as activated T helper cells, with fibroblast-like synoviocytes (FLS) play a crucial role in the joint destruction during human rheumatoid arthritis (RA). This study was undertaken to investigate the expression of the proinflammatory cytokine macrophage migration inhibitory factor (MIF) by T helper cells, and to assess the role of MIF in overexpression of matrix metalloproteinases (MMPs) in cocultures of FLS from arthritic mice with either Th1 or Th2 cells.
Methods: MIF expression by in vitro-polarized murine Th1 and Th2 cells was determined using 2 different generation protocols. FLS were isolated from the inflamed joints of mice with antigen-induced arthritis. MMP expression was analyzed in cocultures of the FLS with T helper cell subsets. Effects of MIF were blocked by a neutralizing anti-MIF antibody. In addition, analyses were performed on cocultures of either Th1 or Th2 cells with FLS from MIF-deficient mice.
Results: Both Th1 and Th2 cells expressed high quantities of MIF. MMPs were overexpressed by FLS after coculture with both Th1 and Th2 cells. Activated T helper cells were more effective than resting cells. Neutralization of MIF by an anti-MIF antibody led to a marked reduction in MMP expression in Th1- and Th2-stimulated FLS. T helper cells generated from MIF-deficient mice exhibited a T helper cell-specific cytokine profile comparable with that in wild-type cells, except in the expression of MIF, but showed an impaired ability to stimulate MMP expression in FLS.
Conclusion: MIF is an important Th1 and Th2 cell-derived proinflammatory cytokine that stimulates MMP expression in FLS from arthritic mice, and therefore inhibition of MIF might be a promising target for novel therapeutic strategies in human RA.