 Furthermore, the IP receptor can physically unite with the TPα receptor to form an IP-TPα heterodimer complex which, when bound by TXA2, activates predominantly IP-coupled cell signal pathways.The nature and extent of many cellular responses to TP receptor activation are thereby modulated by the IP receptor and this modulation may serve to limit the potentially deleterious effects of TP receptor activation (see following section on Functions).Studies using animals genetically engineered to lack the TP receptor and examining the actions of this receptor's agonists and antagonists in animals and on animal and human tissues indicate that TP has various functions in animals and that these functions also occur, or serve as a paradigm for further study, in humans.