HRH4 and amyotrophic lateral sclerosis: Because H4R controls the infiltration of regulatory T cells (49) for instance during the acute phase of experimental allergic encephalomyelitis (50), its increase in SOD1-G93A symptomatic mice might indeed be consistent with the suppressive action of regulatory T cells that occurs also in ALS mice (51), and with the inhibition of pro-inflammatory microglia in the course of the disease.