Immune response in healthy subjects and uncontrolled, ineffective immune response in patients with genetic HLH.⁶  Perforin and granzymes are secreted via cytotoxic granules, leading to apoptosis of the target cell. Processing of cytotoxic granules requires several steps, including polarization, docking, priming, and fusion with the cell membrane. Genes mutated in FHL-3, FHL-4, and FHL-5 and in the immunodeficiency syndromes CHS and GS-2 encode proteins that are crucial for these processes.