ICOS and rheumatoid arthritis: The augmented CD4 + CXCR5 + ICOS+ T cell proportions are not attributable to the presence of activated T cells in peripheral blood; although CXCR5 is typically upregulated upon in vivo T cell activation [32], total CD4 + CXCR5+ T cells themselves were not increased in our RA patients with active or inactive disease.