Increased MM cell lysis induced by treatment of PBMCs with Thal and IMiDs is NK cell mediated.

(A) Normal PBMCs were treated with IL-2 for 72 hours and then by Thal 5 μg/mL (upper panel) or IMiD1 5 μg/mL (lower panel) daily for 3 days. Labeled K562 (NK sensitive/LAK sensitive) and unlabeled competitor Raji cells (NK resistant/LAK sensitive) were cultured at ratios of 0.5:1 to 2:1 in a standard ⁵¹Cr release assay at a 30:1 effector-hot target ratio. (B) Normal PBMCs were treated with IL-2 for 72 hours and then by IMiD1 5 μg/mL daily for 3 days. CD4⁺, CD8⁺, CD56⁺, or CD14⁺ cells were depleted (more than 97% depletion by flow cytometry analysis) using immunomagnetic beads immediately before performing a standard ⁵¹Cr release assay using HS Sultan, MM.1S, and K562 cells as targets at a 30:1 effector-target ratio. (C) Normal PBMCs were treated with IL-2 for 72 hours and then by IMiD1 5 μg/mL daily for 3 days. MM cell line targets were treated with antibodies to class I and class II before ⁵¹Cr release assay.