ICOS and rheumatoid arthritis: Our results in pSS fit the RNA sequencing results from circulating memory CD4 T cells in RA patients (sorted based on PD-1hi versus PD-1- and CXCR5 expression), which indicates that the genes for ICOS and PD-1 (ICOS and PDCD1 genes, respectively) were upregulated most strongly in CXCR5+PD-1hi cells [9].