HRH4 and allergic asthma: In a murine model of allergic asthma, the treatment with the H4R agonist 4-methylhistamine resulted in accumulation of FoxP3+ T cells with potent suppressive activity for proliferation.62 Likewise, H4R was described to play a critical role in determining the frequency of Tregs in secondary lymphoid tissues in a model of allergic encephalomyelitis, as it regulates Treg chemotaxis and suppressor activity.