PDCD1 and rheumatoid arthritis: Indeed, administration of a PD-L1 Ig recombinant fusion protein, PD-1-specific toxins [αPD-1-ABD-PE: anti-PD-1 single-chain variable fragment (αPD-1), an albumin-binding domain (ABD) and Pseudomonas exotoxin (PE)], or adenovirus expressing Fc-PD-L1 can reduce the severity of inflammatory diseases [rheumatoid arthritis (RA), colitis, lupus-like nephritis, EAE, systemic lupus erythematosus (SLE) and psoriasis] (Table 1) (78–80, 94, 95).