Fig. 2

Expression of the programmed cell death 1 protein lacking exon 3 (PD-1Δex3) splicing variant in T cells and correlation between PD-1Δex3 messenger RNA (mRNA) levels and cytokines. a Expression of PD-1Δex3 was analyzed in peripheral blood mononuclear cells (PBMCs) of patients with rheumatoid arthritis (RA) (n = 34) or controls [patients with osteoarthritis (OA), n = 18; healthy controls (HC), n = 21) by real-time polymerase chain reaction (RT-PCR). Horizontal bars represent the mean mRNA level within a given group. b Expression of cytokines was analyzed in PBMCs of patients with RA or controls (OA or HC) by RT-PCR. Asterisks indicate statistically significant differences between the groups (p < 0.05). c–h Correlation of PD-1Δex3 mRNA levels with cytokine mRNA levels. The r value indicates the calculated regression coefficient. i–k Mononuclear cells from healthy volunteers were incubated with 0–100 ng/ml of the indicated recombinant human cytokines for 12 h and 24 h. CD4⁺ T cells were then purified for RT-PCR analysis. flPD-1 full-length isoform of programmed cell death 1 protein, TNF-α tumor necrosis factor α, IFN-γ interferon γ, IL interleukin