Figure 2.

Interleukin-15 (IL-15) -activated, but not resting natural killer (NK) cells kill osteoclasts. Autologous NK cells were isolated from peripheral blood mononuclear cells (PBMCs) and cultured with IL-15 (10 ng/ml) until use (around day 10) or cryopreserved and thawed 1 day before use. Osteoclasts were differentiated from PBMCs, harvested, enriched by CD14⁺ depletion, and then re-seeded at 5000 cells/well in a 96-well flat bottom plates. After 24 hr, the osteoclasts were labelled with ⁵¹Cr and co-cultured with different ratios of autologous IL-15-activated NK cells (solid line) or resting NK cells (dotted line). The NK-mediated killing of osteoclasts was measured by release of ⁵¹Cr from osteoclasts to the conditioned media, and % specific lysis was calculated as described in the Materials and methods. The figure shows the results of five independent experiments with five different donors, each set up in triplicate (mean ±  SEM).