Therefore, we currently rely on the CD107a NK cell degranulation assay for the screening diagnosis of primary HLH related to mutations in UNC13D, STX11, STXBP2, RAB27A, LYST, and AP3B1. The most commonly used NK degranulation assay tests rested PBMC stimulated with the myelogenous leukemia cell line K562 (21). Here, LAMP1 is linked to hemophagocytic syndrome.