p21(-/-) fibroblast-like synoviocytes (FLS) migrate more than wild-type (WT) FLS in response to rheumatoid arthritis (RA) synovial fluid (SF). WT and p21(-/-) FLS were introduced to gradients of RA SFs (diluted in PBS) to induce migration. Cell counts are expressed as fold-increase over background migration to PBS (negative control). (a) Combined chemotaxis data analyzed from four separate patients in three independent experiments demonstrates significantly more migration by the p21(-/-) FLS compared with WT FLS (p < 0.05). (b) Representative data from 1 of 3 independent chemotaxis assays performed using RA SF diluted 1:50 from 4 separate patients randomly designated #1 to #4. p21(-/-) FLS migrated significantly (indicated by an asterisk) more than WT cells in response to all four RA SFs tested.