It inhibits receptor activity in the NMDA glutamate receptor subtypes. There are four major subtypes of opioid receptors. The gene encodes a protein which is one of several receptor subtypes for adenosine. It has actions at several 5-HT (serotonin) receptor subtypes. There are three main histological subtypes of malignant mesothelioma&colon; epithelioid, sarcomatous, and biphasic. He identified four adult subtypes of avoidant personality disorder. By reassortment, H3N2 exchanges genes for internal proteins with other influenza subtypes. Nevertheless, several RNA subtypes with distinct functions exist. These cells can differentiate into one of several subtypes, which have different roles. Hence we differentiate between the following subtypes. They also aid in the differential diagnosis of skeletal dysplasia subtypes. Cytokines direct T cells into particular subtypes. Theodore Millon proposes two subtypes of schizotypal. Each of the personality types is usually understood as having three "instinctual subtypes". These are two subtypes or morphs of one species with different strategies.