ADRB2 (Adrenoceptor Beta 2): ADRB2 is a gene that encodes the beta-2-adrenergic receptor, a protein involved in the body’s ‘fight or flight’ response. This receptor plays a key role in relaxing smooth muscles in the airways and blood vessels and serves as a target for medications used to treat asthma and COPD. Genetic variations in ADRB2 can influence an individual’s response to these treatments.