To date, the enhancement of Ab synthesis mediated by IFN-β treatment is not resulting in an excessive Ig production or in an induction of auto-Abs (data not shown and [46]). Rather, this therapy restores via monocyte-mediated bystander mechanisms the correct TLR7 responsiveness of MS-derived B cells, which in this way fully acquire the capacity to mature into Ig-producing cells, similar to HDs. In this

scenario, the study from Warrington et al. [47] is of great interest that demonstrates how naturally occurring polyclonal human Abs (in particular IgM) can strongly promote FK506 concentration remyelination inducing a transient Ca2+ influx in myelin-forming cells. Thus, the ability of IFN-β therapy to induce polyclonal Abs (and in particular IgM) with potential remyelinating activity reveals another mechanism of protection possibly mediated by this drug, that could lead to amelioration of find more neurological symptoms in MS patients. An additional aspect to take into account from our findings is that the deficient TLR7-induced IgM and IgG production observed in MS patients might correlate with worsening of disease or impaired immune responses against infections with TLR7-recognized RNA viruses, such as influenza, or upon vaccination. Many studies have been conducted in this regard. Different groups have reported that the risk of relapse is increased in individuals with MS bacterial or viral infections [48, 49]. In the case of Astemizole influenza,

it was shown that the reduction of infection episodes leads to a lower number of exacerbations in MS sufferers. In a study with 180 RRMS patients, 33% of individuals, who became infected with this virus, developed an acute relapse within 6 weeks [50]. However, randomized, double-blind, placebo-controlled studies during the past decade have shown that influenza vaccination of MS patients neither increases the relapse rate nor worsens the course of disease [51]. Indeed, the administration

of standard vaccines in MS patients is considered safe worldwide, it follows the same recommendations as in healthy adults and actually should be recommended to MS patients in order to avoid attacks of the disease [52]. Having all this in mind, it cannot be excluded that our data on the reduced level of secreted Abs in response to TLR7 stimulation can have a role in the exacerbation of relapses observed in MS-affected individuals along episodes of influenza infection. The increasing recognition that viruses, and in particular EBV, can be etiological factors driving the development of MS or other autoimmune diseases in genetically susceptible individuals further strengthens the potential of administering anti-viral therapies to people affected by these disorders [12]. In line with this view, the increased TLR7 gene expression observed upon IFN-β might be part of a specific antiviral program induced by this cytokine that could counteract dysregulated responses to viral infection in MS patients.