Crosstalk between CD4 T cells and synovial fibroblasts from human arthritic joints promotes hyaluronan-dependent leukocyte adhesion and inflammatory cytokine expression in vitro

•HA content and organization in ECM are indicators of inflammation in joint disease.•We studied fibroblast-like synoviocytes (FLS) from arthritis subjects (OA and RA)•Co-cultures of RA FLS with activated CD4 T cells generated a HA-enriched ECM that was adherent for monocytes.•Both OA and RA co-cultures elicited significant increases in IL1β, TNF, and IL6.•Blocking HA synthesis reduced expression of IL6, IL1β, and TNF in the co-cultures.•HA-enriched ECM generated by our co-cultures with human joint FLS is pathogenic.