Key Role of the CD56(low)CD16(low) Natural Killer Cell Subset in the Recognition and Killing of Multiple Myeloma Cells

Natural Killer (NK) cells play a pivotal role in the immunosurveillance of Multiple Myeloma (MM), but it is still undefined whether the NK cell functional properties underlying their protective activity against MM are confined to distinct NK cell populations. Interestingly, herein we report that the CD56(low)CD16(low) NK cell subset displayed higher cytolytic activity compared to the other NK cell subsets (i.e., CD56(high)CD16(+/−), CD56(low)CD16(high)) against MM cells and its activity was impaired in MM patients. Decreased DNAM-1 expression levels were observed on the CD56(low)CD16(low) NK cells during MM progression. Evaluating NK cell subset frequency after autologous hematopoietic stem cell transplantation, we found that CD56(low)CD16(low) NK cells recovered earlier after transplantation. Overall, our data denote a key role of CD56(low)CD16(low) subpopulation in the killing of MM cells and suggest that the reconstitution of CD56(low)CD16(low) subpopulation after HSCT could be a useful approach of adoptive immunotherapy in the treatment of relapsed/refractory MM patients.