Defective Neutrophil Function Research Articles

Flow Cytometric Assay of Respiratory Burst Capacity in Peripheral Blood Monocytes of Gaucher Type 1 Patients

Abstract Background: There is an apparently increased tendency toward infections in patients with Gaucher disease, possibly due to defective neutrophil function rather than a decreased neutrophil count. Since macrophages are the main cell type affected in Gaucher disease, our aim was to determine the contribution of these cells to the susceptibility of Gaucher patients to infection by studying the respiratory burst capacity of peripheral blood monocytes. Methods: The study was performed in eleven Gaucher type 1 patients and eleven sex and age matched control subjects by measuring peripheral blood monocytes’ respiratory burst capacity using flow cytometry. The respiratory burst capacity was measured as dihydrorhodamine-123 median fluorescence in patients and respective controls. Results: There was no statistical difference in the median fluorescence among the patients and respective controls (p>0.05) after phorbol 12-myristate 13-acetate stimulation. Also, statistical difference was not reached among patients treated with enzyme replacement therapy at the time and those untreated. Conclusions: Flow cytometry might represent a more accurate and more reliable measure of respiratory burst compared to the methods of other researchers. Respiratory burst disturbance in monocytes does not seem to contribute to increased susceptibility to infection in Gaucher patients.

212: Innate neutrophil function is regulated locally through IL-6 control of prostaglandins

Interleukin-6 (IL-6) is vital for competent anti-microbial host defense. Mice deficient in IL-6 showed an inability to appropriately control bacterial peritonitis (5 × 108 cfu Staphylococcus epidermidis) and displayed both increased dissemination and reduced bacterial clearance. This response was reversed through local reconstitution of IL-6 trans-signaling using a chimeric sIL-6R-IL-6 fusion protein (termed HDS). Administration of HDS (10–1000 ng/ml) to infected IL-6−/− mice promoted bacterial clearance and reduced bacteremia in a dose-dependent fashion. This response was associated with improved resolution of the acute phase response and a more rapid normalization of body temperature. To define the mechanisms governing IL-6 involvement in anti-microbial immunity, we first developed an ex vivo flow cytometric assay to simultaneously monitor neutrophil respiratory burst and phagocytosis. Bacterial stimulation of circulating blood neutrophils from IL-6−/− and IL-6R−/− mice showed comparable effector function to that displayed by WT controls. Thus, IL-6 deficiency is not associated with an inherent defect in neutrophil function. However, evaluation of infiltrating neutrophils isolated by lavage from the peritoneal cavity of infected IL-6−/− and IL-6R−/− mice showed significantly reduced respiratory burst and phagocytic activity. Interleukin-6 therefore controls responses local to the site of infection and is consistent with the activation of non-hematopoietic stromal cells by IL-6 and sIL-6R. In human peritoneal mesothelial cells and peritoneal membranes from infected mice, IL-6 trans-signaling promoted cyclooxygenase-2 (COX2) expression. Blockade of IL-6 signaling in infected WT mice with the antagonist sgp130 or anti-IL-6R antibodies inhibited peritoneal COX2 expression. Mass spectrometry for the COX2 products, prostaglandin-E2 (PGE2) prostaglandin-D2 (PGD2) in lavage samples from infected mice showed that the generation of PGD2, but not PGE2, was impaired in IL-6 deficiency. Here, PGD2 levels correlated with the number of infiltrating neutrophils undergoing respiratory burst. These studies suggest IL-6 signaling regulates the effector characteristics of infiltrating neutrophils through local control of immuno-regulatory prostaglandin production.

Impairment of Mitochondrial–Nuclear Cross Talk in Neutrophils of Patients with Type 2 Diabetes Mellitus

Increased leukocyte apoptosis is intrinsically linked to disease patho-physiology, susceptibility to and severity of infections in type 2 diabetes mellitus (T2DM) patients. A consistent defect in neutrophil function is considered central to this increased risk for infections. Although redox imbalance is considered a potential mediator of these associated complications, detailed molecular evidence in clinical samples remains largely undetected. The study consisted of three groups (n=50 each) of Asian Indians: early diagnosed diabetic patients, cases with late-onset diabetic complications and age and gender-matched healthy controls. We evaluated mitochondrial oxidative stress, levels of nuclear DNA damage and apoptosis in peripheral blood neutrophils isolated from T2DM patients. We observed that in both early and late diabetic subjects, the HbA1c levels in neutrophils were altered considerably with respect to healthy controls. Increased oxidative stress observed in both early and late diabetics imply the disentanglement of fine equilibrium of mitochondria-nuclear cross talk which eventually effected the augmentation of downstream nuclear γH2AX activation and caspase-3 expression. It would be overly naïve to refute the fact that mitochondrial deregulation in neutrophils perturbs immunological balance in type 2 diabetic conditions. By virtue of our data, we posit that maneuvering mitochondrial function might offer a prospective and viable method to modulate neutrophil function in T2DM. Nevertheless, similar investigations from other ethnic groups in conjunction with experimental evidences would be a preeminent need. Obviously, our study might aid to comprehend this complex interplay between mitochondrial dysfunction and neutrophil homeostasis in T2DM.

The effect of bisphosphonate therapy on neutrophil function: a potential biomarker

Bisphosphonate-related osteonecrosis of the jaws (BRONJ) occurs subsequent to intravenous and oral bisphosphonate exposure in a small subset of patients. The identification of the pathophysiologic mechanisms has not been fully elucidated. Evidence of concurrent bacterial colonization at sites of bone necrosis, previous reports of neutrophil-related complications in some patients taking some bisphosphonates, along with perturbed neutrophil function in bisphosphonate-treated mice, suggest an innate immune role in the development of BRONJ. This study investigated neutrophil function in BRONJ patients to determine if neutrophil functional defects may serve as a potential biomarker for BRONJ susceptibility. Two populations were studied: patients with BRONJ and those beginning intravenous pamidronate. Healthy control patients were used for comparison. Twenty-three patients with BRONJ and five patients who were beginning pamidronate therapy provided neutrophil samples from the mouth (oral rinses) and from blood. Neutrophils from the population of patients with BRONJ and from those post-pamidronate treatment showed lower reactive-oxygen species production and impaired chemotaxis relative to controls. These data suggest that a compromise in neutrophil function may be a potential biomarker for BRONJ susceptibility.

Effects of acute and chronic low density lipoprotein exposure on neutrophil function

Mounting evidence suggests that obesity and the metabolic syndrome have significant but often divergent effects on the innate immune system. These effects have been best established in monocytes and macrophages, particularly as a consequence of the hypercholesterolemic state. We have recently described defects in neutrophil function in the setting of both obesity and hypercholesterolemia, and hypothesized that exposure to elevated levels of lipoproteins, particularly LDL its oxidized forms, contributed to these defects. As a model of chronic cholesterol exposure, we examined functional responses of bone marrow neutrophils isolated from non-obese mice with diet-induced hypercholesterolemia compared to normal cholesterol controls. Chemotaxis, calcium flux, CD11b display, and F-actin polymerization were assayed in response to several chemoattractants, while neutrophil cytokine transcriptional response was determined to LPS. Following this, the acute effects of isolated LDL and its oxidized forms on normal neutrophils were assayed using the same functional assays. We found that neutrophils from non-obese hypercholesterolemic mice had blunted chemotaxis, altered calcium flux, and normal to augmented CD11b display with prolonged actin polymerization in response to stimuli. In response to acute exposure to lipoproteins, neutrophils showed chemotaxis to LDL which increased with the degree of LDL oxidation. Paradoxically, LDL oxidation yielded the opposite effect on LDL-induced CD11b display and actin polymerization, and both native and oxidized LDL were found to induce neutrophil transcription of the monocyte chemoattractant MCP-1. Together these findings suggest that chronic hypercholesterolemia impairs neutrophil functional responses, and these defects may be in part due to protracted signaling responses to LDL and its oxidized forms.

Vitamin-D deficiency is associated with chronic bacterial colonisation and disease severity in bronchiectasis

IntroductionVitamin-D deficiency has been linked to an increased risk of respiratory infections. The objective of this study was to determine the frequency and clinical importance of vitamin-D deficiency in patients...

Infections in myelodysplastic syndromes.

Myelodysplastic syndromes are associated with a risk of severe infections. While neutropenia is likely to be the main predisposing factor, several other immune defects have been reported, including impaired neutrophil function, B-, T- and NK-cell defects and the possible consequences of iron overload due to red blood cell transfusions. The advanced age of most patients, their frequent comorbidities, and the fact that drugs such as hypomethylating agents and lenalidomide, which are effective in myelodysplastic syndromes but can transiently worsen neutropenia, may increase the risk of infection and their severity in this context. The majority of infections in myelodysplastic syndromes are bacterial, while the incidence of fungal infections is not well known and viral infections seem to be rare. No prophylactic measures against infections have demonstrated efficacy in myelodysplastic syndromes. However, pending more data, we propose here some recommendations for the management of patients with myelodysplastic syndromes. In the future, an important contribution can be made by prospective trials testing the efficacy of prophylactic and therapeutic approaches to infection in these patients, especially in the context of the new drugs available for myelodysplastic syndromes.

Intrapulmonary Administration of Leukotriene B4 Augments Neutrophil Accumulation and Responses in the Lung to Klebsiella Infection in CXCL1 Knockout Mice

In prior studies, we demonstrated that 1) CXCL1/KC is essential for NF-κB and MAPK activation and expression of CXCL2/MIP-2 and CXCL5/LPS-induced CXC chemokine in Klebsiella-infected lungs, and 2) CXCL1 derived from hematopoietic and resident cells contributes to host immunity against Klebsiella. However, the role of CXCL1 in mediating neutrophil leukotriene B(4) (LTB(4)), reactive oxygen species (ROS), and reactive nitrogen species (RNS) production is unclear, as is the contribution of these factors to host immunity. In this study, we investigated 1) the role of CXCL1 in LTB(4), NADPH oxidase, and inducible NO synthase (iNOS) expression in lungs and neutrophils, and 2) whether LTB(4) postinfection reverses innate immune defects in CXCL1(-/-) mice via regulation of NADPH oxidase and iNOS. Our results demonstrate reduced neutrophil influx, attenuated LTB(4) levels, and decreased ROS and iNOS production in the lungs of CXCL1(-/-) mice after Klebsiella pneumoniae infection. Using neutrophil depletion and repletion, we found that neutrophils are the predominant source of pulmonary LTB(4) after infection. To treat immune defects in CXCL1(-/-) mice, we intrapulmonarily administered LTB(4). Postinfection, LTB(4) treatment reversed immune defects in CXCL1(-/-) mice and improved survival, neutrophil recruitment, cytokine/chemokine expression, NF-κB/MAPK activation, and ROS/RNS production. LTB(4) also enhanced myeloperoxidase, H(2)O(2,) RNS production, and bacterial killing in K. pneumoniae-infected CXCL1(-/-) neutrophils. These novel results uncover important roles for CXCL1 in generating ROS and RNS in neutrophils and in regulating host immunity against K. pneumoniae infection. Our findings suggest that LTB(4) could be used to correct defects in neutrophil recruitment and function in individuals lacking or expressing malfunctional CXCL1.

Neutropenia in Glycogen Storage Disease 1b (GSD1b)

Abstract 4791Neutropenia and recurrent infections are common manifestations of glycogen storage disease 1b (GSD1b), a disease caused by mutations in G6PT1, the glucose 6 phosphate transporter 1 gene. Patients with GSD1b have complex defects in neutrophil deployment and function. GSD1b causes recurrent infections – gingivitis, mouth ulcers, respiratory infections, abscesses and enterocolitis. Granulocyte colony-stimulating factor (G-CSF) has been used to treat these patients for more than 2 decades.We reviewed the presentations, manifestations, complications and G-CSF treatment for 54 GSD1b patients (31 adults and 23 children) at Duke University, the University of Florida and through the Severe Chronic Neutropenia International Registry at the University of Washington. Observational data were available on most patients for at least 3 years (mean = 12 years, median = 13 years, range = 1 to 23 years). Available data showed that before treatment with G-CSF, all of these patients had mild to moderate neutropenia; the mean of the median absolute neutrophil count (ANC) was 0.839 × 109/L ± 0.165 SEM (median = 0.503 × 109/L, range = 0.038 to 7.665 × 109/L). All of the patients also had recurrent infections; the most common events were mouth ulcers, otitis and skin abscesses. There were 7 patients who had enterocolitis prior to G-CSF treatment.G-CSF therapy was initiated at various ages ranging from birth to age 30 (mean = 6 years, median = 4 years). Initial daily doses of G-CSF ranged from 0.50 to 63.28 mcg/kg/day (mean = 5.86, median = 3.65) and were generally titrated upward to achieve a normal neutrophil count. The mean ANC on treatment was 2.598 × 109/L ± 0.136 SEM (median = 1.856 × 109/L, range = 0.0 to 12.645 × 109/L). G-CSF treatment was uniformly associated with an increase in blood neutrophils and reduced patterns of infection. In most patients the symptoms of enterocolitis improved within a few days to a few weeks after starting G-CSF therapy. An increase in spleen size also commonly occurred. In 630 patient-years of observation, there have been 3 deaths attributable to the following causes: 1 subject died of sepsis, 1 subject died of complications from hepatomegaly and neutropenia, and 1 subject died 6 years after a liver transplant. The subject developed AML 5 years after the liver transplant while receiving a combination of immunosuppressant drugs.Patients with GSD1b associated neutropenia respond well to G-CSF with reduced infections and symptoms of enterocolitis. Long-term complications are infrequent and G-CSF is well tolerated in most patients. Disclosures:Dale:Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Boxer:Amgen: Equity Ownership.

Educational paper

The neutrophilic granulocyte (neutrophil) is the most important cellular component of the innate immune system. A total absence of neutrophils or a significant decrease in their number leads to severe immunodeficiency. A mature neutrophil, released from the bone marrow, should be able to migrate from the blood towards the tissues, following a chemotactic gradient to a pathogen. In order to be neutralized, this pathogen has to be recognized, phagocytosed, and destroyed by lytic enzymes contained in the neutrophil's granules and reactive oxygen species formed by the enzyme complex NADPH oxidase. Rare genetic defects leading to the loss of each one of these biological properties of the neutrophil have been described and are associated with immunodeficiency. This review provides a summary of the normal development and biological functions of neutrophils and describes the diseases caused by defects in neutrophil number and function.

Defective neutrophil function underlies the absence of T cell recruitment into challenge sites during elicitation of contact sensitivity in gld/perforin-/- mice (60.7)

Abstract Contact hypersensitivity (CHS) is a CD8 T cell mediated response to hapten sensitization and challenge of the skin. Hapten-primed CD8 T cell infiltration into the skin challenge site is not observed until 12-16 h post-challenge and requires prior neutrophil infiltration and activation within the site. The neutrophil activities required to direct this T cell infiltration to mediate CHS responses are undefined. Although primed CD8 T cells do not express FasL or perforin, CHS responses to 2, 4-dinitrofluorobenzene (DNFB) are absent in gld/perforin-/- mice. ELISPOT analyses indicated equivalent priming of DNFB-specific CD8 cells in sensitized wild-type (WT) and gld/perforin-/- mice. Whereas DNFB-primed CD8 T cells from WT or gld/perforin-/-mice transferred CHS responses to naïve WT recipients, WT CD8 T cells did not transfer the response to gld/perforin-/- mice. Neutrophil infiltration into the challenge site of sensitized gld/perforin-/- and WT mice was equivalent at 6 h post-challenge but T cell infiltration was absent in the challenge site of gld/perforin-/- mice at 18 h. This T cell infiltration and the CHS response were restored by transferring WT neutrophils i.v. to sensitized gld/perforin-/- mice at challenge. Neutrophils from sensitized WT mice expressed high levels of FasL and perforin mRNA. These results indicate that neutrophil expression of FasL and perforin required to direct effector CD8 T cell recruitment into the skin challenge site to mediate CHS responses.

P52 Neutrophil dysfunction: a potential biomarker of poor prognosis in acute liver failure?

IntroductionIn acute liver failure (ALF) an exaggerated systemic inflammatory response can result in neutrophil activation with subsequent tissue damage from release of proteolytic enzymes and reactive oxygen species, contributing to...

Recent advances in the understanding of genetic defects of neutrophil number and function

Neutrophils are amongst the first immune cells to arrive at sites of infection and play an important role as the host's first line of defence against invading pathogens. Defects of neutrophil number or function are usually recognized clinically by recurrent infections that often are life-threatening. Over the last few years, a number of genetic mutations have been discovered to be the basis for congenital neutropenia, adding to our understanding of the molecular basis of these diseases. While many genetic mutations that cause severe congenital neutropenia result in a differentiation block at the promyelocyte stage, defects of neutrophil function are more heterogeneous on clinical, genetic and mechanistic levels. In this review we discuss recent advances in our understanding of the genetic and molecular basis of human neutrophil disorders.

Refractory Polyarticular Gouty Arthritis as a Manifestation of Immune Reconstitution Inflammatory Syndrome

Immune reconstitution inflammatory syndrome (IRIS) describes the initial clinical deterioration some patients manifest upon initiation of effective antiretroviral therapy (ART) for HIV infection. In this report we describe a case of IRIS manifesting as polyarticular gout, a previously unreported rheumatological manifestation of IRIS. A 53-year-old HIV-infected man with a history of intermittent attacks of gout and an initial CD4 count of 112 cells/microL and a viral load of >100,000 copies/mL presented to our institution with severe, refractory, polyarticular gout approximately 4 weeks after initiating ART. At this point, the patient demonstrated significant gains in his CD4 counts (103 cells/microL) and a greater than 3 log decline in his HIV-1- viral load. This episode was prolonged lasting for approximately 10 weeks and required hospitalization for the management of pain and control of inflammation. The temporal associations of this attack with the initiation of ART and the observed immunologic reconstitution make IRIS a clinical possibility.Monosodium urate crystals through their interactions with interleukin 1- beta, and neutrophilic synovitis play a critical role in the pathophysiology of gout. Defects in both neutrophil and macrophage function and imbalances in the cytokine milieu are documented in HIV infected patients. The introduction of ART results in restoration of neutrophil and macrophage function, declines in levels of the anti-inflammatory cytokine IL-10, and increases in levels of proinflammatory cytokines including IL-1 beta, which may provide the necessary milieu for the precipitation of attacks of severe polyarticular gout in the context of ART initiation.

Role of TLR2 and TLR4 on human neutrophil functions against Paracoccidioides brasiliensis

Paracoccidioides brasiliensis (Pb) is the aetiological agent of paracoccidioidomycosis, a systemic mycosis endemic in Latin America. The infection can be acquired by inhalation of airborne conidia that reach the lung alveoli, where they transform into yeast cells, the infective form [1]. Many people are exposed to the fungus, but only a small number develop clinical symptoms, suggesting that both innate and adaptive mechanisms are important in fungus clearance [2–5]. The host innate immune response against fungus has been well characterized, and several studies have clearly shown the role of phagocytic cells. In this context, in last years, various studies have focused on the role of neutrophils [6]. Some in vitro studies suggest that Pb-infected macrophages induce the onset of extravascular neutrophilia by releasing chemotactic peptides [7]. Heavy neutrophil infiltration in the lungs of Pb-infected mice at early acute infection was correlated with the release of keratinocytederived chemokine (KC) and macrophage inflammatory protein-1a (MIP-1a), two important neutrophil chemoattractants [8]. In consequence of these chemotactic processes, massive neutrophil infiltration is found in infected tissues from patients with paracoccidioidomycosis [9] and in the early lesions of experimentally infected animals [10, 11]. Neutrophils from infected individuals can kill Pb [12]. However, experiments using more sensitive methods showed that despite their phagocytic capacity, these neutrophils are unable to digest Pb in vitro, indicating that a defect of neutrophil function may represent a susceptibility factor [13]. Further, studies in mice strongly suggest that lack of fungicidal activity correlates with defect in neutrophil activation because only those neutrophils from P. brasiliensis-sensitized mice exhibited efficient fungicidal *Department of Microbiology and Immunology, Biosciences Institute, Sao Paulo State University, Botucatu, S.P., Brazil; and Botucatu Blood Center, School of Medicine, Sao Paulo State University, Botucatu, S.P., Brazil

Inflammatory Bowel Disease in CGD Reproduces the Clinicopathological Features of Crohn's Disease

Patients with chronic granulomatous disease (CGD), a rare congenital disorder characterized by defective neutrophil function, frequently develop an inflammatory bowel disease similar to Crohn's disease. The clinical presentations and concordance between the features of the bowel disease in these two conditions have never been formally evaluated. Retrospective case note analysis of all adult patients with CGD treated at a tertiary care hospital. A total of 25 eligible patients were identified. Of these, 14 (56%) had experienced gastrointestinal symptoms in the preceding 3 years; and 11 (44%) had documented gastrointestinal inflammation not secondary to infection, manifesting throughout the alimentary canal including the upper gastrointestinal tract (45%), small intestine (27%), colon (73%), and rectum (73%). All had discontinuous inflammation and perianal involvement, and approximately half (55%) demonstrated epithelioid granulomata on histology. All patients fulfilled the Lennard-Jones criteria for the diagnosis of Crohn's disease. Therapeutic responses were observed in five patients to 5-aminosalicylates, and in individual patients to thalidomide, interferon-gamma, azathioprine, infliximab, and intestinal resection. There are striking clinical and pathological resemblances between the bowel diseases observed in CGD and Crohn's disease, supporting the possibility of mechanistic similarities in their pathogenesis. Patients with CGD appear particularly prone to developing perianal disease.

Defective neutrophil and lymphocyte function in leucocyte adhesion deficiency

We report a Chinese girl with the moderate phenotype of leucocyte adhesion deficiency (LAD), presenting with persistent omphalitis and recurrent soft tissue infections. She had subnormal adhesion-dependent neutrophil functions, such as chemotaxis and chemiluminescence response to a particulate stimulant (opsonised zymosan). Despite her adequate humoral response to documented herpes simplex virus type 1, parainfluenza type 2 and adenovirus infection in vivo, there was marked impairment in the generation of plaque-forming cells (PFC) driven by pokeweed mitogen (PWM) in vitro. IgM PFC were less severely affected than IgG and IgA PFC, probably because IgM production is less dependent on T cell help than IgA and IgG production. The patient's B cells and accessory cells had reduced function compared with the control subsets, while helper function of her CD4+ cells was virtually absent in the PWM-driven PFC assay. She also had marked defect in natural killer cell activity. The proliferation of her lymphocytes was normal to several plant lectins, including phytohaemagglutinin, concanavalin A and PWM, but markedly defective to OKT3.

Testing Human Biologicals in Animal Host Resistance Models

The purpose of immunotoxicity testing is to obtain data that is meaningful for safety assessment. Host resistance assays are the best measure of a toxicant's effect on the overall ability to mount an effective immune response and protect the host from infectious disease. An outline is presented for immunotoxicological evaluation using host resistance assays. The influenza virus host resistance model is useful to evaluate the overall health of the immune system and is one of the most thoroughly characterized host resistance models. Viral clearance requires all aspects of the immune system to work together and is the ultimate measure of the health of the immune system in this model. Mechanistic immune functions may be included while measuring viral clearance and include: cytokines, macrophage activity, natural killer (NK) cell activity, cytotoxic T-lymphocyte (CTL) activity, and influenza-specific IgM and IgG. Measurement of these immunological functions provides an evaluation of innate immunity (macrophage or NK activity), an evaluation of cell-mediated immunity (CMI) (CTL activity), and an evaluation of humoral-mediated immunity (HMI) (influenza-specific IgM or IgG). Measurement of influenza-specific IgM or IgG also provides a measurement of T-dependent antibody response (TDAR) since influenza is a T-dependent antigen. There are several targeted host resistance models that may be used to answer specific questions. Should a defect in neutrophil and/or macrophage function be suspected, Streptococcus pneumoniae, Pseudomonas aeruginosa, or Listeria monocytogenes host resistance models are useful. Anti-inflammatory pharmaceuticals or therapeutics for rheumatoid arthritis or Crohn's disease that target TNFα may also be evaluated for immunotoxicity using the S. pneumoniae intranasal host resistance assay. Marginal zone B (MZB) cells are required for production of antibody to T-independent antigens such as the polysaccharide capsule of the encapsulated bacteria that are so prominent in causing blood-borne infections and pneumonia. Intravenous infection with Streptococcus pneumoniae, an encapsulated bacterium, results in a blood-borne infection that requires MZB cells for clearance. The systemic S. pneumoniae host resistance assay evaluates whether a therapeutic test article exerts immunotoxicity on MZB cells and measures the T-independent antibody response (TIAR). Suppression of CMI or in some cases HMI may result in reactivation of latent virus that may result in a fatal disease such as progressive multifocal leukoencephalopathy (PML). The murine cytomegalovirus (MCMV) reactivation model may be used to evaluate a pharmaceutical agent to determine if suppression of CMI or HMI results in reactivation of latent virus. Candida albicans is another host resistance model to test potential immunotoxicity. Host resistance assays have been the ultimate measure of immunotoxicity testing for environmental chemicals and pharmaceutical small molecules. Human biologicals are now an important component of the drug development armamentarium for biotech and pharmaceutical companies. Many human biologicals are fusions of IgG, and/or target immune mediators, immunological receptors, adhesion molecules, and/or are indicated for diseases that have immune components. It is therefore necessary to thoroughly evaluate human biological therapeutics for immunotoxicity. Numerous biologicals that are pharmacologically active in rodents can be evaluated using well-characterized rodent host resistance assays. However, biologicals not active in rodents may use surrogate biologicals for testing in rodent host resistance assays, or may use host resistance assays in genetically engineered mice that mimic the effect of the human biological pharmacological agent.

Neutrophil dysfunction in alcoholic hepatitis superimposed on cirrhosis is reversible and predicts the outcome

Mortality in patients with alcoholic hepatitis (AH) remains high, and although corticosteroids are widely used for treatment, the results vary considerably. In AH, neutrophils are primed and infiltrate the liver to produce injury, but paradoxically, the main cause of death in such patients is infection. Our prospective study addressed this paradox of primed neutrophils on the one hand and increased risk of infection on the other. We hypothesized that the full activation of neutrophils by a humoral factor such as endotoxin renders them unable to respond to further bacterial challenge. We analyzed neutrophil oxidative burst and phagocytosis in whole blood by fluorescence-activated cell sorting analysis in 63 alcoholic patients with cirrhosis and patients with cirrhosis with superimposed AH (cirrhosis+AH). In 16 patients, ex vivo studies determined whether the removal of endotoxin restored neutrophil function. A resting burst greater than or equal to 55[corrected]%, indicating neutrophil activation and a reduced phagocytic capacity lower than 42%, was associated with significantly greater risk of infection, organ failure, and mortality. This defective neutrophil function was transmissible through patients' plasma to normal neutrophils, and patients' neutrophil function could be restored by normal plasma. The ex vivo removal of endotoxin from patients' plasma decreased the resting burst and increased the phagocytic function. Our study provides the rationale for a goal-directed approach to the management of patients with cirrhosis and AH, in which the assessment of neutrophil function may be an important biomarker to select patients for immunosuppressive therapy. The neutrophil dysfunction in cirrhosis and AH is reversible, with endotoxin-removal strategies providing new targets for intervention.

Imerslund-Grasbeck Syndrome Associated With Recurrent Aphthous Stomatitis and Defective Neutrophil Function

Vitamin B(12) deficiency is a well-known cause of recurrent aphthous stomatitis (RAS). However, the mechanism by which this deficiency causes the stomatitis is not well understood. Imerslund-Grasbeck syndrome (IGS) causes vitamin B(12) deficiency and proteinuria due to a defect in the vitamin B(12) receptor. We sought to determine whether the RAS observed in IGS patients is associated with neutrophil dysfunction. We report 3 infants with vitamin B(12) deficiency due to IGS, who presented with borderline or normal hemoglobin concentrations, RAS, and a neutrophil function defect. All 3 patients were homozygous for a splice site mutation affecting exon 4 of the AMN gene. A direct correlation was observed between low serum vitamin B12 levels and defective neutrophil function (low chemotaxis and elevated superoxide production) in the patients. Vitamin B(12) therapy led to an immediate resolution of aphthous stomatitis and full correction of neutrophil function. We demonstrated that serum vitamin B(12) deficiency is associated with a neutrophil chemotactic defect and RAS in IGS patients. We suggest that the RAS observed in these patients is due to this defect.