Several studies have suggested the involvement of SP in experimental arthritis (Levine et al., 1984; Ahmed et al., 1995; Seegers et al., 2003) and in rheumatoid arthritis (Hernanz et al., 1993; Menkes et al., 1993; Miller et al., 2000; Grimsholm et al., 2005; Dirmeier et al., 2008). Here, TFF2 is linked to rheumatoid arthritis.