Affecting the effectors: JAK inhibitors modulation of immune cell numbers and functions in patients with rheumatoid arthritis.

INTRODUCTION

The Janus kinase family includes four members - JAK1, JAK2, JAK3, TYK2 - that are selectively associated with type I and II cytokine receptors. Jak-inhibitors (Jakinibs) are a new class of drugs for treating inflammatory diseases. Five Jakinibs are currently available for Rheumatoid Arthritis (RA): tofacitinib, baricitinib, upadacitinib, filgotinib and peficitinib. Considering the role of cytokines and growth factors in immune cell survival and activation, the anti-proliferative and suppressive effects of Jakinibs on these cells are predictable.

AREAS COVERED: This review summarizes Jakinibs' effects on immune populations in vitro and in vivo. In vitro, Jakinibs affected T and B lymphocytes, monocytes, neutrophils and dendritic cell proliferation. T helper, B cell differentiation, and cytokine secretion . Accordingly, changes in the number of lymphocytes, natural killer (NK) cells, and neutrophils have been reported during the randomized clinical trials with all the Jakinibs, reverting after drug withdrawal.

EXPERT OPINION: In vitro and in vivo studies showed that the numbers and the function of immune cells are influenced by Jakinibs. Nonetheless, their effects do not seem to represent a major safety issue as these changes do not correlate with the onset of serious infection despite the increased rates of herpes zoster reactivation.