It was discovered that the main effect (immunosuppressive activity) of S1P1 receptor agonists correlates with the selectivity for cells expressing a combination of S1P1 receptors and Gai2 or Gai3, and that the side effect (cardiotoxicity) of S1P1 receptor agonists correlates with the selectivity for cells expressing a combination of S1P1 receptors and Gai1.