MRGPRX2 and airway hyperresponsiveness: However, both the number of MRGPRX2+ MCs and overall levels of MRGPRX2 expression were increased in lung biopsies from patients who had died from asthma (318), suggesting that MRGPRX2 may be upregulated in MCs within the inflamed airway microenvironment and potentially play a functional role in airway hyperresponsiveness.