MMP3 and rheumatoid arthritis: Under the conditions described, MIF stimulation showed no effect on secretion of MMP-1, MMP-3, and MMP-13 proteins, because these proteins were not detected in 48-hour MIF-stimulated RA synovial fibroblast culture media by ELISA, whereas control experiments with TNF-α (1.5 nM) increased the concentration of MMP-1, MMP-3, and MMP-13 in the supernatants (data not shown).