Interleukin 21 as a new possible player in pemphigus: Is it a suitable target?

• Interleukin (IL)-21 is a novel potential player in pemphigus.
• IL-21 is involved in pemphigus progression via different signaling pathways associated with various immune responses.
• Inhibition of IL-21 or its receptor may cause the relatively and gradually improvement of pemphigus patients.
• Tofacitinib and anti-IL-21 monoclonal antibody, NNC114-0006 seem to be the possible IL-21 activity blockers in pemphigus.

Pemphigus is a rare autoimmune disease, which could be fatal without treatment. Recently, target therapy is increasingly being used in different autoimmune diseases. However, there are limited studies associated with target therapy in pemphigus. In this study, it was tried to identify the role of interleukin (IL) -21 in patients with pemphigus. Based on the available studies on the role of IL-21 associated with several cells, including T cells, B cells, natural killer (NK) cells, natural killer T (NKT) cells, mast cells as well as regulatory B cells and regulatory T cells, the possible roles of this cytokine in pemphigus were discussed in detail. It was found that IL-21 is a crucial cytokine associated with pemphigus disease, which has not been discussed in this disease yet. It is able to promote T helper (Th) 2, Th17, T follicular helper (Tfh), CD8 + cytotoxic T lymphocytes (CTLs), NK and NKT cells. It also causes the production of immunoglobulin (Ig)G in addition to the decrease of Tregs. All the mentioned alterations seem to be involved in disease progression via different signaling pathways. Inhibition of these changes must cause improvement of disease severity. By inhibition of IL-21 or its receptor, it is expected that patients with severe pemphigus experience relative and gradual improvement. This inhibition could be induced by tofacitinib, which was approved by the US Food and Drug Administration as a treatment for rheumatoid arthritis patients, or anti-IL-21 monoclonal antibody, NNC114-0006. However, more studies are needed to confirm it as a promising therapy.