Flow cytometric analysis showed that 2.7 ± 0.5% (mean ± standard deviation [SD] of four independent experiments) of RA FLS expressed ICAM-1 in serum-free medium, and the ratio of cells expressing ICAM-1 markedly increased up to 44.5 ± 11.7% after stimulation with TNF-α (Fig. 7). This evidence concerns the gene ICAM1 and rheumatoid arthritis.