Fig. 6

(a) Principle physiopathology of FLH2. Homozygous mutations in PRF1 gene cause loss of perforin protein in lytic granules of immune cells such as NK and cytotoxic T cells (1). This functional loss leads to defective killing of infection agents (2) and causes overactivation and expansion of immune cells, concomitant with high level secretion of cytokines (3). Activated lymphocytes and macrophages infiltrate tissues, causing tissue damage as well as spontaneous phagocytosis of blood cells (4). (b) FLH2 in-vitro model employed in this study. NK92 cells engineered using CRISPR/Cas genome editing approach to target PRF1 gene exon 2 (1). Selected clones defective for perforin induced with PMA and ionomysin (2), and cocultured with and without MSCs (3). Among several soluble immunomodulatory factors secreted by MSCs, IL-10 and IL-4 are induced in coculture supernatant concomitantly with diminished release of proinflammatory cytokines IFN-γ and TNF-α from NK92 cells (4). G-CSF granulocyte-stimulating factor, GM-CSF granulocyte–macrophage-stimulating factor, IDO indoleamine 2,3-dioxygenase, IL interleukin, IFN interferon, MSC mesenchymal stem cell, NK natural killer, PGE2 prostaglandin E2, PMA phorbol myristate acetate, sHLA-G5 soluble human leukocyte antigen-G5, TNF tumor necrosis factor