An actin cytoskeletal barrier inhibits lytic granule release from natural killer cells in patients with Chediak-Higashi syndrome.

BACKGROUND: Chediak-Higashi syndrome (CHS) is a rare disorder caused by biallelic mutations in the lysosomal trafficking regulator gene (LYST), resulting in formation of giant lysosomes or lysosome-related organelles in several cell types. The disease is characterized by immunodeficiency and a fatal hemophagocytic lymphohistiocytosis caused by impaired function of cytotoxic lymphocytes, including natural killer (NK) cells. OBJECTIVE: We sought to determine the underlying biochemical cause of the impaired cytotoxicity of NK cells in patients with CHS. METHODS: We generated a human cell model of CHS using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) technology. We used a combination of classical techniques to evaluate lysosomal function and cell activity in the model system and super-resolution microscopy to visualize F-actin and lytic granules in normal and LYST-deficient NK cells. RESULTS: Loss of LYST function in a human NK cell line, NK92mi, resulted in inhibition of NK cell cytotoxicity and reproduced other aspects of the CHS cellular phenotype, including the presence of significantly enlarged lytic granules with defective exocytosis and impaired integrity of endolysosomal compartments. The large granules had an acidic pH and normal activity of lysosomal enzymes and were positive for the proteins essential for lytic granule exocytosis. Visualization of the actin meshwork openings at the immunologic synapse revealed that the cortical actin acts as a barrier for secretion of such large granules at the cell-cell contact site. Decreasing the cortical actin density at the immunologic synapse or decreasing the lytic granule size restored the ability of LYST-deficient NK cells to degranulate and kill target cells. CONCLUSION: The cortical actin and granule size play significant roles in NK cell cytotoxic function. We present evidence that the periodicity of subsynaptic actin is an important factor limiting the release of large lytic granules from NK cells from patients with CHS and could be a novel target for pharmaceutical intervention.

Congenital Hypopigmentary Disorders with Multiorgan Impairment: A Case Report and an Overview on Gray Hair Syndromes.

The term congenital hypopigmentary disorders refers to a wide group of heterogeneous hereditary diseases, clinically characterized by inborn pigmentary defects of the iris, hair, and/or skin. They include Gray Hair Syndromes (GHSs), a rare group of autosomal recessive genodermatosis hallmarked by inborn silvery gray hair. GHSs encompass Griscelli, Chediak⁻Higashi, Elejalde, and Cross syndromes, which are all characterized by a broad spectrum of severe multisystem disorders, including neurological, ocular, skeletal, and immune system impairment. In this manuscript, we describe in detail the clinical, trichoscopic, and genetic features of a rare case of Griscelli syndrome; moreover, we provide an overview of all the GHSs known to date. Our report highlights how an accurate clinical examination with noninvasive methods, like trichoscopy, may play a crucial rule in diagnosis of rare and potentially lethal genetic syndromes such as Griscelli syndrome, in which timely diagnosis and therapy may modify the clinical course, quality of life, and likelihood of survival.

Subtle differences in CTL cytotoxicity determine susceptibility to hemophagocytic lymphohistiocytosis in mice and humans with Chediak-Higashi syndrome.

Perforin-mediated cytotoxicity is important for controlling viral infections, but also for limiting immune reactions. Failure of this cytotoxic pathway leads to hemophagocytic lymphohistiocytosis (HLH), a life-threatening disorder of uncontrolled T-cell and macrophage activation. We studied susceptibility to HLH in 2 mouse strains (souris and beige(J)) and a cohort of patients with partial defects in perforin secretion resulting from different mutations in the LYST gene. Although both strains lacked NK-cell cytotoxicity, only souris mice developed all clinical and histopathologic signs of HLH after infection with lymphocytic choriomeningitis virus. The 2 strains showed subtle differences in CTL cytotoxicity in vitro that had a large impact on virus control in vivo. Whereas beige(J) CTLs eliminated lymphocytic choriomeningitis virus infection, souris CTLs failed to control the virus, which was associated with the development of HLH. In LYST-mutant patients with Chediak-Higashi syndrome, CTL cytotoxicity was reduced in patients with early-onset HLH, whereas it was retained in patients who later or never developed HLH. Thus, the risk of HLH development is set by a threshold that is determined by subtle differences in CTL cytotoxicity. Differences in the cytotoxic capacity of CTLs may be predictive for the risk of Chediak-Higashi syndrome patients to develop HLH.

Familial hemophagocytic lymphohistiocytosis: a model for understanding the human machinery of cellular cytotoxicity.

Cytotoxic T lymphocytes, natural killer cells, and NKT cells are effector cells able to kill infected cells. In some inherited human disorders, a defect in selected proteins involved in the cellular cytotoxicity mechanism results in specific clinical syndromes, grouped under the name of familial hemophagocytic lymphohistiocytosis. Recent advances in genetic studies of these patients has allowed the identification of different genetic subsets. Additional genetic immune deficiencies may also induce a similar clinical picture. International cooperation and prospective trials resulted in refining the diagnostic and therapeutic approach to these rare diseases with improved outcome but also with improved knowledge of the mechanisms underlying granule-mediated cellular cytotoxicity in humans.

Unrelated cord blood transplantation can restore hematologic and immunologic functions in patients with Chediak-Higashi syndrome.

CHS is a rare hereditary fatal disease, if not treated. APs occur in 85% of patients and are usually the main cause of mortality, and HSCT from HLA-matched related and unrelated donors is the only effective treatment for CHS and prevents recurrences of APs. We reviewed the records of three patients with CHS who underwent UCBT at KHCC. Records were examined for clinical features at the time of UCBT, conditioning regimens, morbidities, and outcomes. Conditioning comprised BU, cyclophosphamide, horse ATG, and etoposide. All patients tolerated the conditioning well. Two patients are alive, one with mixed and the other with full donor chimerism; hematologic and immunologic defects of CHS have been corrected in both patients. They show no evidence of recurrences of APs and have normal growth and development. In patients with CHS who lack HLA-matched related and unrelated donors, UCBT is a suitable alternative source of stem cells to restore immunologic and hematologic functions and prevent AP relapses, even in mixed chimeric states. Long follow-up and close monitoring are essential to evaluate the long-term benefits of using UCBT in patients with CHS.

Understanding neutropenia secondary to intrinsic or iatrogenic immune dysregulation.

As a key member of the innate and adaptive immune response, neutrophils provide insights into the hematopoietic and inflammatory manifestations of inborn errors of immunity (IEI) and the consequences of immunotherapy. The facile recognition of IEI presenting with neutropenia provides an avenue for hematologists to facilitate early diagnosis and expedite biologically rationale care. Moreover, enhancing the understanding of the molecular mechanisms driving neutropenia in IEI-decreased bone marrow reserves, diminished egress from the bone marrow, and decreased survival-offers an opportunity to further dissect the pathophysiology driving neutropenia secondary to iatrogenic immune dysregulation, eg, immune checkpoint inhibitors and chimeric antigen receptor T-cell therapy.

Chédiak-Higashi gene in humans. II. The selectivity of the defect in natural-killer and antibody-dependent cell-mediated cytotoxicity function.

Antibody-dependent cell-mediated cytolysis (ADCC) of human tumor cells by FcR(+) nonadherent effector lymphocytes as well as natural killer (NK) activity was markedly impaired in Chediak-Steinbrinck-Higashi Syndrome (C-HS) patients. Compared to a more than 400-fold defect in NK activity in terms of lytic units, the abnormal ADCC response in C-HS donors was 24-fold below normal suggesting a partial but not complete overlap of lymphocytes or lytic mechanisms responsible for ADCC and NK. The ADCC mechanism against erythrocyte targets, however, was normal, thereby suggesting a qualitative difference in these two forms of ADCC. Other effector-cell functions against tumor-cell targets were normal as measured by (a) spontaneous cytolysis mediated by monocytes, (b) spontaneous cytostasis mediated by neutrophils, and (c) lectin-dependent cytolysis mediated by neutrophils. Although one C-HS patient was low in lectin-dependent cytolysis mediated by lymphocytes, the other C-HS patient was normal, thereby suggesting that cytolytic T function was not linked to the NK-ADCC defect. In addition, the proliferative response to T-dependent mitogens was also relatively normal. These results, combined with other studies showing normal cell-mediated and humoral immunity in these same patients, suggest that patients with C-HS have an immunodeficiency which is selective for NK and ADCC activity.

The mouse gut T lymphocyte, a novel type of T cell. Nature, origin, and traffic in mice in normal and graft-versus-host conditions.

Lymphocytes of the mouse intestinal mucosa, identified in tissue sections or purified suspensions of intraepithelial lymphocytes as T cells (gut T lymphocytes [GTL]), were studied in normal mice or in beige mice (the equivalent of the Chediak-Higashi syndrome in man, characterized by giant granules in various cell types, including mast cells). Mice were studied in normal or in germ-free conditions, or during a graft versus host (GVH) reaction resulting from the injection of parental thymocytes into lethally irradiated F1 mice, a condition leading to massive accumulation of T lymphocytes of donor origin in the host gut mucosa. In normal as well as in GVH conditions, a high percentage of the gut IE lymphocytes contain granules (up to 80% in the beige mouse). These granules have ultrastructural, hostochemical and other features resembling those of mast cell granules; in beige mice, up to 50% of them can be shown to contain histamine. Granulated T cells are also found in the lamina propria. It appears that the GTL may progressively lose their surface T antigens when the granules become more developed. Kinetics of [3H]TdR labeling of the GTL, transfer experiments with T cells of various origins, selective [3H]TdR labeling and selective irradiation of the Peyer's patches (PP), and effect of thoraic duct (TD) drainage led to the conclusion that GTL are the progeny of T cells stimulated to divide in the PP microenvironment, which endows them with a gut-homing tendency. From the PP, these cells follow a cycle, migrating to the TD and to the blood to colonize the whole intestinal mucosa, the majority of them as dividing cells undergoing a single round of traffic, with some probably able to recirculate and becoming a more long-lived variety. Antigenic stimulation within the PP is necessary for the emergence of GTL progenitors, but their gut-homing property is unrelated to the antigen as shown with fetal gut grafts, notably in GVH where grafts syngeneic to the host or donor become similarly infiltrated by GTL. On the basis of their properties and of further evidence to be reported elsewhere, it is proposed that GTL belong to a special class of T lymphocytes, related to the immune defenses of the mucosal systems in general, and capable of acting as progenitors of mucosal mast cells.

Chédiak-Higashi gene in humans I. Impairment of natural-killer function.

Natural-killer (NK)-cell function was profoundly depressed in donors homozygous for the Chediak-Steinbrinck-Higashi syndrome (C-HS) gene when compared with age- and sex-matched normals. This apparent defect was not simply a result of a delayed response because little cytolysis was evident in kinetics experiments even after 24 h of incubation. NK cells from C-HS donors failed to lyse adherent (MDA, CEM, and Alab) or nonadherent (K562 and Molt-4) tumor cell lines or nontransformed human fetal fibroblasts. Therefore, the apparent C-HS defect was not a result of a shift in target selectivities. In addition, the depressed reactivity did not appear to be a result of suppressor cells or factors because: (a) enriched NK populations (nonadherent lymphocytes bearing receptors for the Fc portion of IgG) from C-HS donors were low in NK-cell function, (b) C-HS mononuclear cells did not inhibit the cytotoxicity of normal cells in coculture experiments, and (c) cells from the C-HS donors remained poorly reactive even after culture for up to 7 d. The nature of the defective NK activity in C-HS patients is not clear but may lie within the lytic mechanism rather than at the level of the recognition structure or population size because the frequency of target-binding cells was normal. In vitro NK activity could be partially restored by interferon treatment. Combined with the results presented in the following paper (4), these observations suggest that the C-HS gene causes a selective immunodeficiency disorder, mainly involving NK cells. This finding, in conjunction with the high incidence of spontaneous possibly malignant, lymphoproliferative disorders in these patients, may have important implications regarding the theory of immune surveillance mediated by NK cells.

Production of plasminogen activator by human natural killer cells. Large granular lymphocytes.

In this report we have used highly purified populations of natural killer (NK) cells: large granular lymphocytes (LGL). This study demonstrates that freshly isolated and interleukin 2-cultured LGL produce the specific neutral serine protease, plasminogen activator (PA). We have found that the enzyme is expressed in both an extracellular form as well as in a cell-associated form. Upon subcellular distribution the latter form of the enzyme is associated with a cell-surface membrane-enriched fraction. LGL PA exists in multiple molecular weight forms ranging from 100,000 to 26,000. Interferon (IFN), the major positive regulator of NK cytolytic activity, caused a substantial enhancement of cell-associated, but not extracellular, PA. In contrast, LGL isolated from patients with Chediak-Higashi syndrome, who are known to be defective in NK activity, displayed low PA activity, altered morphology, and low NK killing relative to LGL isolated from normal donors. The possible role of LGL PA in the lysis of tumor cells by NK cells, either directly or indirectly, is discussed.

Deficient peptide loading and MHC class II endosomal sorting in a human genetic immunodeficiency disease: the Chediak-Higashi syndrome.

The Chediak-Higashi syndrome (CHS) is a human recessive autosomal disease caused by mutations in a single gene encoding a protein of unknown function, called lysosomal-trafficking regulator. All cells in CHS patients bear enlarged lysosomes. In addition, T- and natural killer cell cytotoxicity is defective in these patients, causing severe immunodeficiencies. We have analyzed major histocompatibility complex class II functions and intracellular transport in Epstein Barr Virus-transformed B cells from CHS patients. Peptide loading onto major histocompatibility complex class II molecules and antigen presentation are strongly delayed these cells. A detailed electron microscopy analysis of endocytic compartments revealed that only lysosomal multilaminar compartments are enlarged (reaching 1-2 micron), whereas late multivesicular endosomes have normal size and morphology. In contrast to giant multilaminar compartments that bear most of the usual lysosomal markers in these cells (HLA-DR, HLA-DM, Lamp-1, CD63, etc.), multivesicular late endosomes displayed reduced levels of all these molecules, suggesting a defect in transport from the trans-Golgi network and/or early endosomes into late multivesicular endosomes. Further insight into a possible mechanism of this transport defect came from immunolocalizing the lysosomal trafficking regulator protein, as antibodies directed to a peptide from its COOH terminal domain decorated punctated structures partially aligned along microtubules. These results suggest that the product of the Lyst gene is required for sorting endosomal resident proteins into late multivesicular endosomes by a mechanism involving microtubules.

Morphological and functional analysis of beige (Chèdiak-Higashi syndrome) mouse mast cells with giant granules.

Chèdiak-Higashi syndrome is a rare autosomal recessive disease that causes hypopigmentation, recurrent infections, mild coagulation defects and neurological problems. Beige mice carry a mutation in the lysosome trafficking regulator (LYST) gene and display some of the key characteristics of human Chèdiak-Higashi syndrome, in particular, a high susceptibility to infection due to aberrant natural killer (NK) cell and polymorphonuclear leucocyte function. Morphological analysis of beige mice reveals the presence of enlarged lysosomes in a variety of cell types, including leucocytes, hepatocytes, fibroblasts and renal tubule cells. To examine the process of granule maturation and degranulation in beige mice mast cells, morphological studies have been conducted using a combination of electrophysiological techniques; however, few functional studies have been conducted with mast cells, such as mediator release. The aim of the present study was to determine the morphological and functional characteristics of skin and peritoneal mast cells and bone marrow-derived mast cells of homozygous (bg/bg) and heterozygous (bg/+) beige mice and wild-type (+/+) mice. The histamine concentration was lower in the peritoneal and bone marrow-derived mast cells of bg/bg mice compared with those of bg/+ and +/+ mice, but the histamine release response was potentiated. In vivo studies of passive cutaneous anaphylaxis showed no differences between bg/bg mice and either bg/+ or +/+ mice. Although bg/bg mast cells with enlarged granules display specific exocytotic processes in vitro, the consequences of mast cell activation in beige mice were similar to those of wild-type mice in vivo.

Deficiency of active natural killer cells in the Chediak-Higashi syndrome. Localization of the defect using a single cell cytotoxicity assay.

This study investigated the defective natural killer (NK) cell activity in two patients with the Chediak-Higashi syndrome (CHS) using both a standard 51-chromium release microcytoxicity and a single cell-in-agarose assay against K562 and Molt-4 target cells. CHS patients were deficient in overall maximum NK capacity, but had normal percentages of potentially cytotoxic target bindng cells. the relative number of TBC that could kill bound targets (i.e., "active" NK cells) was significantly depressed in CHS patients when compared with normal controls. The diminished CHS active NK cells that were present, however, were capable of recycling and lysing multiple target cells during the assay period. In vitro interferon (INF) treatment of normal and CHS effector cells did not alter target cell binding, but did increase the maximum NK capacity, percentage of active NK cells and the maximum recycling capacity, as well as the rate of lysis. These studies indicate that the depression of NK activity in patients with CHS is secondary to a deficiency of active NK cells. The CHS active NK cells that are present, however, are capable of normal target lysis and recycling. Potentially cytotoxic pre-NK cells, which can bind but not kill target cells, can be activated by in vitro IFN to develop lytic activity. Thus, IFN treatment may be of potential benefit to the immune surveillance network of CHS patients by activating a population of pre-NK cells to express their cytotoxic potential.

Natural killer (HNK-1+) cells in Chediak-Higashi patients are present in normal numbers but are abnormal in function and morphology.

Children with the Chediak-Higashi (CH) syndrome are known to have abnormalities of natural killer (NK) cell function. We used the HNK-1 monoclonal antibody that reacts specifically with human NK and K cells to distinguish whether this abnormality was due either to a numerical deficiency of NK cells or a defect in their ability to function. In eight CH patients, a significant proportion of their blood mononuclear cells (10--19%) expressed the HNK-1 differentiation antigen. The level of NK cells in the five children with CH syndrome was higher than for age-matched normal controls (15.8% vs. 5.8%, P less than 0.001). When HNK-1+ cells were isolated with a fluorescence-activated cell sorter, the NK cells from CH patients were a homogeneous population of lymphocytes with a single large granule rather than the multiple small granules seen in Nk cells from normal individuals. The purified HNK-1+ cells from the CH patients had minimal NK or K cell function. The CH syndrome thus includes a functionally defective population of NK cells that retain the capability of expressing the HNK-1 differentiation antigen.

Lytic granules, secretory lysosomes and disease.

Lytic granules harbour many of the dangerous apoptosis-inducing molecules of the immune system, including perforin, granzymes and Fas ligand. Safe transport, storage and release of these lytic components is vital. As a secretory lysosome, the lytic granule is able to accomplish these roles, as well as conferring the lysosomal functions of cytotoxic T lymphocytes and natural killer cells. Secretory lysosomes are common to many other haemopoietic cells and also melanocytes. Many of the proteins used in lysosomal secretion are found in both melanocytes and hemopoietic cells, and are dysfunctional in genetic diseases with defects in these proteins. The genetically heterogeneous Hermansky-Pudlak syndrome represents an excellent model for revealing proteins involved in secretory lysosome functioning. However, studies of this disease reveal differences between the various different types of secretory lysosomes, including lytic granules.

Herpesvirus saimiri-transformed CD8+ T cells as a tool to study Chediak-Higashi syndrome cytolytic lymphocytes.

Cytolytic CD8+ T lymphocytes are the main cell type involved in the fatal lymphoproliferative-accelerated phase of the Chediak-Higashi syndrome (CHS). To generate a cellular tool to study the defects of this T cell subset in vitro, we have used Herpesvirus saimiri, a lymphotropic virus that transforms human T lymphocytes into extended growth and in addition, endows them with natural killer (NK) features. Transformed CHS CD8+ T cells were generated and characterized in comparison with healthy controls. The results showed that transformed CHS T cells maintained the defects described in primary CHS lymphocytes, such as giant secretory lysosomes and impaired NK and T cell receptor/CD3-induced, perforin-mediated cytolytic activity [which, however, could be restored after extended culture in the presence of interleukin-2 (IL-2)]. Upon activation with phorbol ester plus calcium ionophore or upon extended culture with IL-2, transformed CHS T cells showed normal, perforin-independent plasma membrane CD178/CD95L/FasL-mediated cytolytic activity but negligible secretion of microvesicle-bound CD95L. Transformed (and primary) CHS T cells were otherwise normal for cytolysis-independent activation functions, such as proliferation, surface expression of several activation markers including major histocompatibility complex class II, and cytokine or surface activation-marker induction. Therefore, the CHS protein [CHS1/LYST (for lysosomal traffic regulator)] can be dispensable for certain NK and T cell cytolytic activities of activated CHS CD8+ T lymphocytes, but it seems to be required for microvesicle secretion of CD95L. We conclude that transformed CHS T cells may be useful as a tool to study in vitro the relative role of CHS1/LYST in NK and T lymphocyte cytolysis and antigen presentation.

NK cell effector functions in a Chédiak-Higashi patient undergoing cord blood transplantation: Effects of in vitro treatment with IL-2.

NK cell cytotoxicity in Chédiak-Higashi syndrome (CHS) is strongly impaired as lytic granules are not released upon NK-target cell contact, contributing to several defects typical of this severe immunodeficiency. Correction of NK cell defects in CHS should improve the outcome of hematopoietic stem-cell transplantation, proposed as therapy. We investigated NK cell functions in a CHS patient before and after cord-blood transplantation, and the ability of in vitro IL-2 treatment to restore them. Before the transplant, the strong defect in NK cell-mediated natural and antibody-dependent cytotoxicity, as well as in IFN-γ production, could be restored up to normal levels by in vitro IL-2 treatment. This cytokine also caused the appearance of smaller lysosomal granules and their orientation towards the NK-target cell contact area, thus suggesting that IL-2 had a more general capacity to restore NK cell effector functions. Moreover after the transplant, although the successful engraftment, NK cell cytotoxicity resulted still partially impaired at one year, almost normal at ten years and, anyhow, fully recovered by in vitro IL-2 treatment. Taken together, our results indicate that IL-2 had a wide capacity to restore NK cell effector functions, being able to reverse the altered cytotoxic activity, lytic granule pattern, and cytokine production observed in the CHS patient.

Neutrophil functional disorder in childhood.

Neutrophil functional disorders thought to be uncommon, yet important as a cause of morbidity and mortality in infants and children. During the first years of life, when the immune system is still not completely mature, when the viral infections are frequent and antibiotic overuse can damage and alter the immune response, the inadequate nutrition followed with iron deficient anemia and malnutrition can lead the child`s organism in state of immunodeficiency. Sometimes is difficult to distinguish at the beginning weather the cause of patient suffering from frequent infections is existing of primary immunodeficiency disorder or the cause of the immunodeficiency state is just from exogenous factors. Fortunately, primary immune deficiencies are rare diseases and only 6-7% of all of them, due to the neutrophilic functional disorders. Unfortunately, many exogenous and environmental factors have influence to the immune system, and the percentage of secondary caused neutrophilic functional disorders is much higher and should be considered when children are investigated for immunodeficiency. So, when to suspect neutrophil functional disorder? The hallmarks for diseases related to the neutrophilic functional disorders are discussed in this article.

Monocytes, macrophages, and their diseases in man.

Mononuclear phagocytes are a widely distributed system of cells involved in host defense functions, immunologic reactions, disposal of unwanted organic and inorganic materials, and synthesis of biologically active compounds such as complement components and prostaglandins. The system includes early precursor cells in the bone marrow, blood monocytes, alveolar and peritoneal macrophages, sinusoidal lining cells in the spleen, and Kupffer cells in the liver. We have recently come to understand the biology of these interesting cells and the diseases they produce.

Lymphocyte subsets in Chediak-Higashi patients.

Peripheral blood lymphocyte subsets were studied in 6 Chediak-Higashi patients and 12 family members. The lymphocyte subsets were characterized by monoclonal antibody reagents and fluorescence flow-cytometry. An increase in OKT8 (suppressor/cytotoxic) and a decrease in OKT4 (helper) cell populations was observed in all patients studied. No correlation was seen between the clinical status (presence or absence of the lymphoproliferative phase) and the percentage of the lymphocyte subsets. The patient's mothers also had an increased percentage of OKT8-positive cells. The significance of these findings is discussed regarding the patients clinical course.