To find out which CD150 isoforms are expressed in CLL B cells, we focused on the canonical transmembrane CD150 isoform (mCD150) that has two ITSM signaling motifs in cytoplasmic domain, the secreted CD150 isoform (sCD150) that lacks the transmembrane region, and a novel CD150 isoform (nCD150) with an alternative cytoplasmic tail without known signaling motifs. Here, SLAMF1 is linked to B-cell chronic lymphocytic leukemia.