CD4 T cells in 98 blood samples of patients with RA (n = 78) or SpA (n = 20) were quantified by flow cytometry after stimulation with VZV antigen and the polyclonal stimulus Staphylococcus aureus enterotoxin B (SEB), and they were characterized for expression of cytokines (interferon-γ, tumor necrosis factor [TNF]-α, interleukin [IL]-2) and markers for activation (CD69), differentiation (CD127), or functional anergy programmed death 1 molecule [PD-1], cytotoxic T-lymphocyte antigen 4 [CTLA-4]. Here, CTLA4 is linked to rheumatoid arthritis.