T cell activation initiated via the CD3/TCR complex requires signals provided by the interaction between costimulatory receptors on T cells and their corresponding ligands on accessory cells. Human dermal fibroblasts are reported to be deficient in this costimulatory activity and normally cannot serve as accessory cells for activation of resting T cells. We examined the contribution of human synovial fibroblasts to costimulatory activity for resting T cells.
Synovial fibroblast, dermal fibroblast, and umbilical cord endothelial cell cultures were established. These cell lines were co-cultured with purified peripheral T cells; and T cell activation was assayed using 3H-thymidine.
Culturing resting T cells with synovial fibroblasts resulted in T cell proliferation with either mitogenic (periodate) or alloantigenic stimulation. This activation was dependent on the addition of interleukin 1 and/or gamma interferon.
In contrast to dermal fibroblasts, synovial fibroblasts are able to provide costimulatory activity for activation of resting T cells.