p85α is an intrinsic regulator of human natural killer cell effector functions

CARD11 dominant negative mutation leads to altered human Natural Killer cell homeostasis

Dominant negative mutations in CARD11 have been reported in patients with immune dysregulation, severe atopic features, and variable T cell alterations. Data on Natural killer (NK) cells from affected patients are lacking. We report on a 12-year-old boy with severe atopic dermatitis, food induced anaphylaxis and hypogammaglobulinemia harbouring a novel de novo heterozygous variant c.169G > A; p.Glu57Lys in CARD11. The dominant negative effect of this mutation was confirmed on both CD4+ and CD8+. CTLA4+Foxp3+CD4+ Tregs were severely reduced. Patient's NK cells showed reduced expression of NKp46, NKG2D and CD69. Patient's CD56bright NK cells showed in vitro impaired production of IFN-γ. Steady state pS6 levels on patient's NK cells were increased and remained elevated upon IL2 + IL12 + IL18 overnight stimulation. Overall, the effect of CARD11 mutation on mTORC1 differs between T and NK cells. These findings may explain the increased susceptibility to viral infections and the reduced immune surveillance in affected patients.

Higher Incidence of B Cell Malignancies in Primary Immunodeficiencies: A Combination of Intrinsic Genomic Instability and Exocytosis Defects at the Immunological Synapse

Congenital defects of the immune system called primary immunodeficiency disorders (PID) describe a group of diseases characterized by a decrease, an absence, or a malfunction of at least one part of the immune system. As a result, PID patients are more prone to develop life-threatening complications, including cancer. PID currently include over 400 different disorders, however, the variety of PID-related cancers is narrow. We discuss here reasons for this clinical phenotype. Namely, PID can lead to cell intrinsic failure to control cell transformation, failure to activate tumor surveillance by cytotoxic cells or both. As the most frequent tumors seen among PID patients stem from faulty lymphocyte development leading to leukemia and lymphoma, we focus on the extensive genomic alterations needed to create the vast diversity of B and T lymphocytes with potential to recognize any pathogen and why defects in these processes lead to malignancies in the immunodeficient environment of PID patients. In the second part of the review, we discuss PID affecting tumor surveillance and especially membrane trafficking defects caused by altered exocytosis and regulation of the actin cytoskeleton. As an impairment of these membrane trafficking pathways often results in dysfunctional effector immune cells, tumor cell immune evasion is elevated in PID. By considering new anti-cancer treatment concepts, such as transfer of genetically engineered immune cells, restoration of anti-tumor immunity in PID patients could be an approach to complement standard therapies.

Emerging insights into human health and NK cell biology from the study of NK cell deficiencies

Human NK cells are innate immune effectors that play a critical roles in the control of viral infection and malignancy. The importance of their homeostasis and function can be demonstrated by the study of patients with primary immunodeficiencies (PIDs), which are part of the family of diseases known as inborn defects of immunity. While NK cells are affected in many PIDs in ways that may contribute to a patient's clinical phenotype, a small number of PIDs have an NK cell abnormality as their major immunological defect. These PIDs can be collectively referred to as NK cell deficiency (NKD) disorders and include effects upon NK cell numbers, subsets, and/or functions. The clinical impact of NKD can be severe including fatal viral infection, with particular susceptibility to herpesviral infections, such as cytomegalovirus, varicella zoster virus, and Epstein-Barr virus. While NKD is rare, studies of these diseases are important for defining specific requirements for human NK cell development and homeostasis. New themes in NK cell biology are emerging through the study of both known and novel NKD, particularly those affecting cell cycle and DNA damage repair, as well as broader PIDs having substantive impact upon NK cells. In addition, the discovery of NKD that affects other innate lymphoid cell (ILC) subsets opens new doors for better understanding the relationship between conventional NK cells and other ILC subsets. Here, we describe the biology underlying human NKD, particularly in the context of new insights into innate immune cell function, including a discussion of recently described NKD with accompanying effects on ILC subsets. Given the impact of these disorders upon human immunity with a common focus upon NK cells, the unifying message of a critical role for NK cells in human host defense singularly emerges.

From Natural Killer Cell Receptor Discovery to Characterization of Natural Killer Cell Defects in Primary Immunodeficiencies

Alessandro Moretta was Professor of Histology at University of Brescia from 1994 to 1997. It was in that period that we met and started a collaboration that continued in the years to follow. He immediately involved us in the production of monoclonal antibodies (mAbs) that allowed the identification and fine characterization of novel receptor molecules that were able to activate or inhibit human Natural Killer cell function, including several antibodies specific for Natural Cytotoxicity Receptor (NCR) and Killer-cell Immunoglobulin-like Receptor (KIR) molecules. These reagents, generated in our laboratory in Brescia, contributed to complete the studies aimed to characterize innate lymphoid NK cells, that had been initiated by Alessandro and his brother Lorenzo in Genoa. Soon, we identified an anti-KIR3DL2 that was subsequently shown to be helpful for the diagnosis and treatment of various forms of cutaneous T cell lymphoma. While in Brescia, Alessandro established a partnership with those of us who were working in the Department of Pediatrics; together, in short time we tackled the goal of studying the role of NK cells in patients with primary immunodeficiencies. This collaboration led to novel discoveries that shed light on the critical role played by NK cells in the immune response against virus and tumors in humans, as best exemplified by our characterization of the molecular mechanisms of impaired control of Epstein-Barr Virus (EBV) infection in patients with X-linked lymphoproliferative (XLP) disease. After Alessandro left Brescia to return to Genoa, our collaboration continued with the same enthusiasm, and even from a distance he remained an extraordinary example of an inspirational and generous mentor. This review is a sign of our gratitude to a mentor and a friend whom we deeply miss.