The infrapatellar fat pad produces interleukin-6-secreting T cells in response to a proteoglycan aggrecan peptide and provides dominant soluble mediators different from that present in synovial fluid.

Objective: The purpose of this study was to investigate the effects of osteoarthritis (OA) peripheral blood mononuclear cell (PBMC) -stimulating proteoglycan aggrecan peptides on T cells present in infrapatellar fat pads (IPFPs) and synovial tissues, and to correlate these findings with mediators present in synovial fluid of OA patients.

Methods: We tested for interleukin-6 (IL-6) -producing T cells in IPFPs of patients with knee OA using ELISPOT. Cytokine and cytotoxic mediator production from OA PBMCs, IPFPs, synovial tissues, and synovial fluids in response to proteoglycan aggrecan peptides were quantified by cytometric bead array.