CD40LG and rheumatoid arthritis: Although an association between CXCL13 and ACPA was observed, it was not as strong a relationship as that seen with RF (IgM RF: r = 0.45 and r = 0.54 in the established and early RA cohorts, respectively; IgG ACPA: r = 0.17 and r = 0.21, respectively).