 found that BNIP3 and BNIP3L play a necessary role in promoting NK cell memory formation.Expression of BNIP3 in NK cells is lowered upon viral infection as NK cell proliferation occurs but returns back to its basal amounts by day 14 and through the contraction phase.By using BNIP3-knockout mice, they found a significant decrease in surviving NK cells suggesting they’re important to maintain survival of NK memory cells.