CTLA4 and rheumatoid arthritis: In PBMC in vitro studies, we observed IRL201805 upregulated expression of the cell surface CTLA-4 on RA peripheral blood mononuclear cells (PBMCs) compared with healthy control samples (control, 8.6 ± 5.1% vs. IRL201805, 13.2 ± 8.4%, n = 23, p = 0.02) (Figure 3A).