BCR and B-cell chronic lymphocytic leukemia: By showing that the spontaneous upregulation of S1PR1 that was observed in a proportion of CLL cases could be reversed by BCR cross-linking and that idelalisib had the greatest effect on CLL cells that did not spontaneously upregulate S1PR1 in culture, the current study adds further weight to the growing idea that the BCR of CLL cells is chronically stimulated in vivo.