Thymic emigration is mediated by the sphingosine-1-phosphate receptor 1 (S1PR1), which is expressed on thymocytes and responds to an S1P gradient (reviewed in [99]), and while its expression has not been examined in ALCL or in the mouse models, it is possible that the presence of a transgenic TCR (as discussed below) might modulate its expression. Here, S1PR1 is linked to anaplastic large cell lymphoma.