Background: The cytokine interferon beta (IFNbeta) is successfully used in the treatment of multiple sclerosis (MS), although there is a high degree of variability in the response. A common mechanism involved in the modulation of responsiveness to cytokines is represented by regulation of their receptor expression through autocrine ligand-mediated loops. The present study is aimed at investigating the regulation of IFNalpha/beta receptor (IFNAR) during IFNbeta therapy in patients with MS and at correlating it with the biologic responsiveness to the cytokine.
Methods: Quantitative PCR measurements of IFNAR-1 and the three IFNAR-2 isoforms were performed in 141 patients after short-term and long-term treatment. Patients were also regularly screened for anti-IFNbeta neutralizing antibodies (NAbs). IFN-inducible myxovirus resistance protein A messenger RNA was used as an indicator of bioactivity.
Results: Pretreatment levels of IFNAR-2 in patients were lower overall than in controls (p = 0.038), and high levels correlated with greater bioactivity. Upon prolonged treatment, NAb-negative patients displayed a state of decreased transmembrane IFNAR-2 expression (p < or = 0.025), whereas levels of soluble IFNAR-2 were slightly increased (p < 0.0001). The presence of NAbs reversed these effects (p < or = 0.0056). In NAb-positive patients, pretreatment expression levels of both transmembrane IFNAR-2 isoforms were significantly lower than in NAb-negative patients (p < or = 0.0089).
Conclusions: Findings show that interferon-alpha/beta receptor (IFNAR)-2 isoforms are important regulators of the responsiveness to endogenous and systemically administered interferon beta (IFNbeta). They show a dual action, agonistic and antagonistic, that influences both the magnitude and the nature of the biologic response to IFNbeta. Levels of IFNAR-2 are regulated with the aim of keeping the body in a state of equilibrium, even when nonphysiologic stimuli are present.