Due to its previously unknown selectin-independent roles and its ability to induce T-cell exhaustion, PSGL-1 has also been proposed as a potential target for immune modulation [22] and humoral immunotherapy [23] because it is highly expressed in lymphoproliferative disorders with plasmocytic differentiation and in multiple myelomas (MMs) as well [23,24,25]. Here, SELPLG is linked to plasma cell myeloma.