Soluble IgG Research Articles

Directed evolution-based discovery of ligands for in vivo restimulation of CAR-T cells.

Chimeric antigen receptor (CAR) T cell therapy targeting CD19 elicits remarkable clinical efficacy in B-cell malignancies, but many patients relapse due to failed expansion and/or progressive loss of CAR-T cells. We recently reported a strategy to potently restimulate CAR-T cells in vivo, enhancing their functionality by administration of a vaccine-like stimulus comprised of surrogate peptide ligands for a CAR linked to a lymph node-targeting amphiphilic PEG-lipid (termed CAR-T-vax). Here, we demonstrate a general strategy to generate and optimize peptide mimotopes enabling CAR-T-vax generation for any CAR. Using the clinical CD19 CAR FMC63 as a test case, we employed yeast surface display to identify peptide binders to soluble IgG versions of FMC63, which were subsequently affinity matured by directed evolution. CAR-T vaccines using these optimized mimotopes triggered marked expansion of both murine CD19 CAR-T cells in a syngeneic model and human CAR-T cells in a humanized mouse model of B cell acute lymphoblastic leukemia (B-ALL), and enhanced control of leukemia progression. This approach thus enables vaccine boosting to be applied to any clinically-relevant CAR-T cell product.

Methadone use is associated with increased levels of sCD14, immune activation, and inflammation during suppressed HIV infection.

Opioid use has negative effects on immune responses and may impair immune reconstitution in persons living with HIV (PLWH) infection undergoing antiretroviral treatment (ART). The effects of treatment with μ opioid receptor (MOR) agonists (e.g., methadone, MET) and antagonists (e.g., naltrexone, NTX) on immune reconstitution and immune activation in ART-suppressed PLWH have not been assessed in-depth. We studied the effects of methadone or naltrexone on measures of immune reconstitution and immune activation in a cross-sectional community cohort of 30 HIV-infected individuals receiving suppressive ART and medications for opioid use disorder (MOUD) (12 MET, 8 NTX and 10 controls). Plasma markers of inflammation and immune activation were measured using ELISA, Luminex, or Simoa. Plasma IgG glycosylation was assessed using capillary electrophoresis. Cell subsets and activation were studied using whole blood flow cytometry. Individuals in the MET group, but no in the NTX group, had higher plasma levels of inflammation and immune activation markers than controls. These markers include soluble CD14 (an independent predictor of morbidity and mortality during HIV infection), proinflammatory cytokines, and proinflammatory IgG glycans. This effect was independent of time on treatment. Our results indicate that methadone-based MOUD regimens may sustain immune activation and inflammation in ART-treated HIV-infected individuals. Our pilot study provides the foundation and rationale for future longitudinal functional studies of the impact of MOUD regimens on immune reconstitution and residual activation after ART-mediated suppression.

Diagnostic Performance of Parasitological, Immunological, Molecular, and Ultrasonographic Tests in Diagnosing Intestinal Schistosomiasis in Fieldworkers From Endemic Municipalities in the Philippines

Schistosomiasis remains to ha/ve a significant public health impact in the Philippines. The Kato-Katz (K-K) technique is the reference standard and most used technique for definitive diagnosis of intestinal schistosomiasis for control programs in endemic regions. However, this has a very low sensitivity when applied in areas of low endemicity and patients with light infection. Hence, this study determined the diagnostic performance of immunological, molecular, parasitological, and ultrasonographic tests in diagnosing intestinal schistosomiasis in endemic municipalities in the Philippines. We performed a community-based cross-sectional study to determine the positivity of schistosomiasis in Leyte, Philippines. The diagnostic performance of five different detection techniques: (1) three stool K-K with duplicate smears; (2) soluble egg antigen IgG ELISA; (3) urine point-of-care circulating cathodic antigen (POC-CCA) test; (4) detection of Schistosoma japonicum circulating DNA (SjcDNA) in serum and urine samples; (5) focused abdominal ultrasound (US), were also obtained in this study. Multiple stool examinations enhanced the sensitivity of K-K from 26.2% (95% CI [16.4, 38.8]) with single stool to 53.8% (95% CI [41.1, 66.1]) and 69.2% (95% CI [56.4, 80.0]) with two and three stools from consecutive days, respectively. Among the SjcDNA nucleic acid amplification test (NAAT)-based detection assays, loop-mediated isothermal amplification (LAMP) PCR using sera had the highest sensitivity at 92.3% (95% CI [82.2, 97.1]) with LAMP consistently identifying more positive cases in both serum and urine samples. This study showed that single stool K-K, which remains the only diagnostic test available in most endemic areas in the Philippines, had low sensitivity and failed to identify most patients with light infection. SjcDNA detection assay and POC-CCA urine test were more sensitive than stool microscopy in detecting schistosomiasis. On the other hand, US was less sensitive than the widely utilized K-K technique in diagnosing schistosomiasis. This study emphasizes the need to revisit the use of single stool K-K in the surveillance and case detection of schistosomiasis in endemic areas of the Philippines. The availability of advanced and more sensitive diagnostic tests will help better control, prevent, and eliminate schistosomiasis in the country.

Detection and functional resolution of soluble immune complexes by an FcγR reporter cell panel

Fc‐gamma receptor (FcγR) activation by soluble IgG immune complexes (sICs) represents a major mechanism of inflammation in certain autoimmune diseases such as systemic lupus erythematosus (SLE). A robust and scalable test system allowing for the detection and quantification of sIC bioactivity is missing. We developed a comprehensive reporter cell panel detecting activation of FcγRs. The reporter cell lines were integrated into an assay that enables the quantification of sIC reactivity via ELISA or a faster detection using flow cytometry. This identified FcγRIIA(H) and FcγRIIIA as the most sIC‐sensitive FcγRs in our test system. Reaching a detection limit in the very low nanomolar range, the assay proved also to be sensitive to sIC stoichiometry and size reproducing for the first time a complete Heidelberger‐Kendall curve in terms of immune receptor activation. Analyzing sera from SLE patients and mouse models of lupus and arthritis proved that sIC‐dependent FcγR activation has predictive capabilities regarding severity of SLE disease. The assay provides a sensitive and scalable tool to evaluate the size, amount, and bioactivity of sICs in all settings.

Combinatorial CAR design improves target restriction

CAR T cells targeting the B lymphocyte antigen CD19 have led to remarkable clinical results in B cell leukemia and lymphoma but eliminate all B lineage cells, leading to increased susceptibility to severe infections. As malignant B cells will express either immunoglobulin (Ig) light chain κ or λ, we designed a second-generation CAR targeting Igκ, IGK CAR. This construct demonstrated high target specificity but displayed reduced efficacy in the presence of serum IgG. Since CD19 CAR is insensitive to serum IgG, we designed various combinatorial CAR constructs in order to maintain the CD19 CAR T cell efficacy, but with IGK CAR target selectivity. The Kz-19BB design, combining CD19 CAR containing a 4-1BB costimulatory domain with an IGK CAR containing a CD3zeta stimulatory domain, maintained the target specificity of IgK CAR and was resistant to the presence of soluble IgG. Our results demonstrate that a combinatorial CAR approach can improve target selectivity and efficacy.

S2627 A Case of K2-Induced Hyperbilirubinemia

INTRODUCTION: Over the last decade, synthetic cannabinoids (SCB) have been marketed as a natural and safer version of marijuana, leading to an increase in its recreational use. We present a case of isolated hyperbilirubinemia caused by K2 and, to our knowledge, this is the first reported case of K2-induced indirect hyperbilirubinemia. CASE DESCRIPTION/METHODS: An 18-year-old male with no significant medical history presented with behavioral changes. He admitted to using K2 daily. His sibling and paternal uncle had Gilbert's syndrome. On physical exam he was withdrawn and agitated. He had Scleral icterus and jaundice. Slit Lamp exam was equivocal. On labs: Total Bilirubin 11.2 mg/dL, Indirect bilirubin 10.8 mg/dL, Urine toxicology positive for marijuana.Serum ceruloplasmin, serum copper, 24h urinary copper excretion, anti-mitochondrial Ab, anti-Nuclear Ab, anti-LKM, Soluble Liver antigen, ferritin, iron, TIBC, A1AT, A1AT phenotype, IgG, IgM, IgA, hepatitis A, B, C serologies, LDH, haptoglobin, uric acid, Coombs test, and G6PD levels were all within normal limits. His peripheral blood smear was normal. Imaging: MRI brain: unremarkable, Liver biopsy:normal hepatic architecture without severe pathological process (Figures 2a and 2b). He was treated with supportive care and indirect hyperbilirubinemia improved. DISCUSSION: • There is no current literature that correlates indirect hyperbilirubinemia and SCB use. In our otherwise healthy patient, this hyperbilirubinemia was likely a consequence of his K2 ingestion. We hypothesize that K2 may impair hepatic glucuronidation which is the process by which indirect bilirubin is converted to direct bilirubin. • During the time of exacerbation of Gilbert's disease, most often the indirect bilirubin levels remain < 5mg/dL. In the case of our patient, he presented with an indirect bilirubin level of 10.8 mg/dL. His work-up excluded other causes of indirect hyperbilirubinemia. • This leads us to hypothesize that K2 may induce significant isolated indirect hyperbilirubinemia in patients with a predisposition to impaired hepatic glucuronidation. • We believe that removal of the insulting agent is required for resolution of the hyperbilirubinemia. • With the use of SCB increasing recreationally, it is crucial we understand the effects these drugs can have. SCB do not appear on standard hospital drug screens. Therefore, a focused history and exam should be obtained from the patient. Our case serves to increase awareness of SCB use as a cause of indirect hyperbilirubinemia.Figure 1Figure (2a).: Liver biopsy stained with Hematoxylin & Eosin, showing normal hepatic architecture with no periductal or ductular inflammatory infiltration.Figure (2b).: Hepatic tissue stained with Periodid acid-Schiff Diastase and for copper; normal pathology & negative copper staining.

Salivary Gland Mucosa-Associated Lymphoid Tissue-Type Lymphoma From Sjögren's Syndrome Patients in the Majority Express Rheumatoid Factors Affinity-Selected for IgG.

ObjectivePatients with Sjӧgren's syndrome (SS) have an increased risk of developing malignant B cell lymphomas, particularly mucosa‐associated lymphoid tissue (MALT)–type lymphomas. We have previously shown that a predominant proportion of patients with SS‐associated salivary gland MALT lymphoma express somatically hypermutated IgM with strong amino acid sequence homology with stereotypic rheumatoid factors (RFs). The present study was undertaken in a larger cohort of patients with SS‐associated MALT lymphoma to more firmly assess the frequency of RF reactivity and the significance of somatic IGV‐region mutations for RF reactivity.MethodsB cell antigen receptors (BCRs) of 16 patients with SS‐associated salivary gland MALT lymphoma were analyzed. Soluble recombinant IgM was produced of 12 MALT lymphoma samples, including 1 MALT lymphoma sample that expressed an IgM antibody fitting in a novel IGHV3‐30–encoded stereotypic IGHV subset. For 4 of the 12 IgM antibodies from MALT lymphoma samples, the somatically mutated IGHV and IGKV gene sequences were reverted to germline configurations. Their RF activity and binding affinity were determined by enzyme‐linked immunosorbent assay and surface plasmon resonance, respectively.ResultsNine (75%) of the 12 IgM antibodies identified in patients with SS‐associated salivary gland MALT lymphoma displayed strong monoreactive RF activity. Reversion of the IGHV and IGKV mutations to germline configuration resulted in RF affinities for IgG that were significantly lower for 3 of the 4 somatically mutated IgM antibodies. In stereotypic IGHV3‐7/IGKV3‐15–encoded RFs, a recurrent replacement mutation in the IGKV3‐15–third complementarity‐determining region was found to play a pivotal role in the affinity for IgG‐Fc.ConclusionA majority of patients with SS‐associated salivary gland MALT lymphoma express somatically mutated BCRs that are selected for monoreactive, high‐affinity binding of IgG‐Fc. These data underscore the notion that soluble IgG, most likely in immune complexes in inflamed tissues, is the principal autoantigen in the pathogenesis of a variety of B cell lymphomas, particularly SS‐associated MALT lymphomas.

THP-1 cells increase TNF-α production upon LPS + soluble human IgG co-stimulation supporting evidence for TLR4 and Fcγ receptors crosstalk

The lipopolysaccharide (LPS) of Gram-negative bacteria is recognized on human monocytes and macrophages by TLR4 and MD2 and induces the production of inflammatory cytokines; the LPS + IgG complexes co-stimulation increases the cytokine production, mediated by the Fc-γRIIa (CD32a). We stimulated human CD14 + monocytes or THP-1 cells with LPS or LPS + soluble human IgG (sIgG) and TNF-α transcription and production, assessed RT-qPCR, ELISA, or flow cytometry, was enhanced by 30% upon LPS + sIgG compared to LPS stimulation. LPS + sIgG co-stimulation affected the NF-κB pathway (p65 phosphorylation and nucleus translocation, and IkB- α degradation). The biochemical inhibition of IRAK 1/4 and Syk kinases suppressed the enhancer effect of LPS + sIgG on TNF- α production, suggesting the involvement of both MyD88 dependent and independent pathways. Our results suggest that during LPS activation, sIgG may participate in a TLR4 - Fc-γR crosstalk.

FcRn mediates fast recycling of endocytosed albumin and IgG from early macropinosomes in primary macrophages

The neonatal Fc receptor (FcRn) rescues albumin and IgG from degradation following endocytosis and thereby extends the half-life of these plasma proteins. However, the pathways for the uptake of these soluble FcRn ligands, and the recycling itinerary of the FcRn-ligand complexes, have not been identified in primary cells. Here, we have defined the recycling of human albumin and IgG in primary mouse macrophages selectively expressing the human FcRn. Albumin is internalised by macropinocytosis; in the absence of FcRn, internalised albumin is rapidly degraded, while in the presence of FcRn albumin colocalises to SNX5-positive membrane domains and is partitioned into tubules emanating from early macropinosomes for delivery in transport carriers to the plasma membrane. Soluble monomeric IgG was also internalised by macropinocytosis and rapidly recycled by the same pathway. In contrast, the fate of IgG bound to surface Fcγ receptors differed from monomeric IgG endocytosed by macropinocytosis. Overall, our findings identify a rapid recycling pathway for FcRn ligands from early macropinosomes to the cell surface of primary cells.

Asparaginase immune complexes induce Fc-γRIII-dependent hypersensitivity in naive mice.

Asparaginase (ASNase) is an important drug for the treatment of leukemias. However, hypersensitivity to ASNase can increase the risk of leukemia relapse. Two mechanisms of ASNase hypersensitivity have been identified in mice. The existence of a pathway involving anti-ASNase IgG and Fc-γ receptor III (Fc-γRIII) implies that IgG and ASNase immune complexes (ICs) could directly induce hypersensitivity. The aim of this study was to detect ASNase ICs in mice after hypersensitivity reactions and determine their role in hypersensitivity. Protein G beads were used to detect plasma ASNase ICs by flow cytometry. Anti-ASNase IgG was purified from the plasma of sensitized mice, and ASNase ICs were prepared ex vivo at various ratios of ASNase to anti-ASNase IgG. The levels of ASNase ICs detected after hypersensitivity reactions correlated with reaction severity (R2 = 0.796; P = 0.0005). ASNase ICs prepared ex vivo required high levels of anti-ASNase IgG for formation, and binding to naive and sensitized immune cells depended on soluble anti-ASNase IgG, antigen:antibody ratio, and Fc-γRIII. Similarly, basophil activation by ASNase ICs depended on the antigen:antibody ratio and Fc-γRIII. Consistent with the ex vivo results, naive mice receiving ASNase ICs developed hypersensitivity reactions. Our data demonstrate that ASNase ICs can directly contribute to the onset and severity of ASNase hypersensitivity.-Rathod, S., Ramsey, M., DiGiorgio, D., Berrios, R., Finkelman, F. D., Fernandez, C. A. Asparaginase immune complexes induce Fc-γRIII-dependent hypersensitivity in naive mice.

Reproducibility of fluid-phase measurements in PBS-treated sputum supernatant of healthy and stable COPD subjects.

PurposeThe purpose of this study was to investigate the reproducibility of fluid-phase measurements in PBS-treated sputum supernatant, processed using the two-step method, of healthy and stable COPD individuals.MethodsNine healthy subjects and 23 stable COPD patients provided sputum twice within 6 days. A two-step sputum processing method was used to obtain PBS-treated supernatant and sputum cells. Soluble protein markers and IgG and IgM autoantibody profiles in PBS supernatant were analyzed using customized microarrays. Repeatability of measurements was assessed by paired-sample testing and an intraclass correlation coefficient, then graphically reported by Bland–Altman plot.ResultsThere was no significant difference between the repeated detection of 8/10 types of soluble protein markers, all 13 types of IgG autoantibodies, and 12/13 types of corresponding IgM autoantibodies in PBS supernatant. The repeatability of measurements in PBS supernatant was substantial to very good for interleukin 6 (IL6), IL8, IL13, IL10, IL33, vascular endothelial growth factor, soluble receptor for advanced glycation end-products, and tumor necrosis factor-α; for IgG autoantibodies against aggrecan, centromere protein B (CENP-B), collagen II, collagen IV, cytochrome C, elastin, heat shock protein 47 (HSP47), HSP70, and La/Sjögren syndrome type B antigen; for IgM autoantibodies against CENP-B, collagen I, collagen II, collagen IV, cytokeratin 18, and HSP70; and for sputum neutrophils, macrophages and eosinophils count. Bland–Altman plots suggested good consistency within repeated measurements. Stable COPD patients differed from healthy subjects in the proportion of neutrophils and eosinophils; relative fluorescence intensity of anti-cytochrome C IgG, anti-aggrecan IgM, and anti-cytochrome C IgM. There was a significant positive correlation for stable COPD patients between sputum anti-collagen II IgG and post-bronchodilator FEV1%.ConclusionWe confirmed fluid-phase measurements in PBS-treated sputum supernatant by high-throughput techniques with good repeatability. We demonstrated the presence of IgG and IgM autoantibodies to multiple antigens in the airways of COPD patients.

Clinical significance of soluble immunoglobulins A and G and their coated bacteria in feces of patients with inflammatory bowel disease

BackgroundImmunoglobulin A (IgA) and IgG are major components in human intestinal mucosal surface and sera, and IgA- or IgG-coated bacteria play a vital role in the intestinal homeostasis. However, the correlation of IgA, IgG and their coated bacteria with the clinical characteristics of inflammatory bowel disease (IBD) has not been fully clarified.MethodsThe levels of soluble IgA and IgG in sera and feces were detected by ELISA, and the percentage of IgA- and IgG-coated bacteria in feces was analyzed by flow cytometry. Crohn’s disease activity index (CDAI) and Simple Endoscopic Score for Crohn’s disease (SES-CD) for Crohn’s disease (CD) or Mayo score and ulcerative colitis endoscopic index of severity (UCEIS) for ulcerative colitis (UC), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were used to evaluate the disease activity.Results178 patients with CD, 75 patients with UC and 41 healthy donors were recruited in this study. We found that the concentrations of soluble IgA and IgG in feces of active IBD patients were significantly higher than those in healthy controls and that the levels of soluble IgA and IgG in feces from IBD patients were positively correlated with CRP, ESR, Mayo score, UCEIS, SES-CD, and CDAI, respectively. Moreover, we also observed that the percentage of IgA- and IgG-coated bacteria markedly increased in feces of IBD patients, especially in CD patients at the age of 17 to 40 years old, with terminal ileal lesions and perianal lesions, as well as from E2 UC patients, and was closely associated with disease activities.ConclusionsThe levels of soluble IgA and IgG and the percentage of IgA- and IgG-coated bacteria strikingly increase in feces of IBD patients and correlate with disease activity.

Essential Domain-Dependent Roles Within Soluble IgG for in vivo Superantigen Properties of Staphylococcal Protein A: Resolving the B-Cell Superantigen Paradox

Staphylococcus aureus is a common commensal and frequent opportunistic pathogen that causes invasive infections that often recur. Co-evolution with the host has led to the development of toxins that affect diverse immune cell types. Recent reports have highlighted the contributions of staphylococcal protein A (SpA). This small oligomeric secreted protein contains 4–5 homologous domains with two distinct immunoglobulin-binding sites; one for IgG Fc domains, while a separate site binds an evolutionarily conserved surface on Fab encoded by VHIII clan related genes. The Fab-binding site has been implicated in in vivo supraclonal VHIII-BCR targeted B-cell depletion by an activation induced death pathway. Yet the concept of a superantigen for B lymphocytes poses a seeming paradox. Unlike TCR that are expressed only in a membrane-associated form, BCR are expressed in both a membrane BCR form and in secreted Ig forms, which permeate virtually every part of the body at high levels. We therefore asked, why circulating immunoglobulin do not block the superantigen properties of SpA? Herein, we show that soluble IgG molecules are not in vivo inhibitors of these B-cell superantigen effects but are instead essential for potentiating these properties. We also show that the Fc subclass of circulating IgG is an indirect critical determinant of the B-cell superantigen effect. In contrast, host FcγR and complement are not required for SpA mediated in vivo B-cell depletion. Unexpectedly, after VHIII-IgG2a pretreatment SpA challenge resulted in fatal anaphylactic reactions, which we speculate may have involved FcγR interactions with mast cells and basophils. Cumulatively, our findings illuminate a cunning and potent molecular strategy by which a bacterial toxin effectively confounds the contributions of host B-lymphocytes to immune defenses.

免疫複合体検出法 (Clq-microplate ELISA) における Clq と可溶性熱会合 IgG との結合への単体 IgG の阻害作用

免疫複合体検出法 (Clq-microplate ELISA) における Clq と可溶性熱会合 IgG との結合への単体 IgG の阻害作用

The Bacterial Enzyme IdeS Cleaves the IgG-Type of B Cell Receptor (BCR), Abolishes BCR-Mediated Cell Signaling, and Inhibits Memory B Cell Activation.

Ag binding to the BCR is a critical step in B cell development and activation, initiating a cascade of signaling events ultimately leading to proliferation, differentiation, or cell death. A bacterial enzyme, IgG-degrading enzyme of Streptococcus pyogenes (IdeS), was shown to specifically cleave IgG molecules below the hinge region of soluble IgG and when IgG is bound to Ag, resulting in one F(ab')2 molecule and one homodimeric Fc fragment. Whether IdeS could also cleave the IgG molecule when it is present in the BCR attached to the B cell membrane in a complex with CD79a and CD79b is unknown. In this article, we present human in vitro and ex vivo data showing that IdeS cleaves the IgG present in the BCR complex and very efficiently blocks Ag binding to the BCR. As a consequence of IdeS cleaving the BCR, signaling cascades downstream of the BCR are blocked, and memory B cells are temporarily silenced, preventing them from responding to antigenic stimulation and their transition into Ab-producing cells.

Blood-brain barrier disruption during spontaneous canine visceral leishmaniasis.

Visceral leishmaniasis is a complex disease caused by Leishmania infantum, and in dogs, besides the classical symptoms, there are descriptions of inflammatory alterations in the brain. Brain inflammation is a strictly controlled process, and as the brain counts on the efficiency of the blood-brain barrier (BBB), we aimed to assess BBB integrity in dogs with spontaneous visceral leishmaniasis. Therefore, we evaluated markers in the cerebrospinal fluid (CSF) and in brain tissue related to BBB disruption and brain inflammation. Elevated albumin quota revealed BBB breakdown, corroborated by increased concentrations of anti-Leishmania antibodies in the CSF. In the brain, albumin and IgG staining formed halos around blood vessels, a classical indicator of BBB leakage. Soluble IgG was also detected in the choroid plexus and ependyma, and in these structures, IgG stained random resident cells. IgG(+) cells and Fcγ-RI(+) cells were identified in the choroid plexus, ependyma and perivascular in the brain parenchyma. The data support the occurrence of BBB disruption in dogs with spontaneous visceral leishmaniasis, and IgG as a key molecule that is capable of initiating and/or maintaining the inflammatory stimuli in the nervous milieu and the CSF as an important disseminator of inflammatory stimuli within the CNS.

IgE low affinity receptor (CD23) expression, Plasmodium falciparum specific IgE and tumor necrosis factor-alpha production in Thai uncomplicated and severe falciparum malaria patients

Previous studies have suggested that Plasmodium falciparum (P. falciparum) specific IgE in the form of immune complexes crosslinking the low-affinity receptor (CD23) on monocyte results in tumor necrosis factor (TNF)-α and nitric oxide (NO) production. However, the roles of these parameters in severity and immune protection are still unclear. This study aimed to determine the association between CD23 expression on monocytes, plasma soluble CD23 (sCD23), total IgE, malaria-specific IgE and IgG, and TNF-α levels in P. falciparum infected patients. We evaluated 64 uncomplicated (UC) and 25 severe patients (S), admitted at the Hospital for Tropical Diseases, Mahidol University, and 34 healthy controls (C) enrolled in 2001. Flow cytometry and enzyme linked immunosorbent assays (ELISA) demonstrated that trends of the CD23 expression, levels of sCD23 and specific IgE were higher in the S group as compared to those in the UC and C groups. Plasma levels of P. falciparum specific IgE in the UC (p=0.011) and S groups (p=0.025) were significantly higher than those in C group. In contrast the TNF-α levels tended to be higher in the UC than those in the S (p=0.343) and significantly higher than those in C (p=0.004) groups. The specific IgG levels in UC were significantly higher than those in S and C (p<0.001) groups. At admission, a strong significant negative correlation was found between specific IgG and sCD23 (r=−0.762, p=0.028), and TNF-α and IgE–IgG complexes (r=−0.715, p=0.002). Significant positive correlations between levels of specific IgE and TNF-α (r=0.575, p=0.010); and sCD23 (r=0.597, p=0.000) were also observed. In conclusion, our data suggest that CD23 expression and malaria-specific IgE levels may be involved in the severity of the disease while TNF-α and the malaria-specific IgG may correlate with protection against falciparum malaria.

An insight on antibody-mediated immune-metabolism in inflammation and homeostasis: the role of Fc gamma receptors in regulation of indolemaine 2,3 dioxygenase activity in dendritic cells (IRM9P.460)

Abstract Indoleamine2, 3-dioxygenase (IDO) is a key immune-modulatory enzyme in Tryptophan catabolism that is highly expressed by Dendritic cells (DCs). Notably, DCs are the main mediators of Fc-dependent anti-inflammatory effects of Intravenous Immunoglobulins (IVIgs) as well as Immune Complexes (ICs)-induced inflammation. Hence, we aimed to study the role of FcγRs in regulation of IDO activity in human DCs from healthy individuals, which remains elusive compared to the well-established role of TLRs. Plasma-pooled human IgG showed no effect on IDO activity in un-stimulated monocyte-derived DCs (Mo-DCs). However, on TLR4 stimulation, IgG down-regulates LPS-induced IDO activity. This counter-regulation was enhanced further, by blocking FcγRIIA, the highest expressed FcγR on Mo-DCs. Interestingly, this effect was elicited by both soluble and plate-bound IgG, resembling IVIgs and ICs, respectively, but with higher potency with soluble IgG. Strikingly, mouse IgG demonstrated a similar effect to human IgG. Herein, we propose a threshold model for IDO regulation through a crosstalk between TLR and FcγRs in homeostatic and inflammatory conditions. IgG was only able to down-regulates TLR-4-induced IDO activity in human DCs, with no effect in the steady state. Furthermore, data suggest that recognition of conserved proteins or glycan moieties of IgG by gamma associated receptors modulate IDO activity. Such insight has potential therapeutic implications for antibody-based immunotherapy.

Chemical modification of peanut conglutin reduces IgE reactivity but not T cell reactivity in peanut-allergic patients

Specific immunotherapy for peanut allergy is associated with significant side-effects. Chemically modified allergens may provide a safer alternative. This study aimed to analyse the immunogenicity and allergenicity of modified peanut conglutin. Native peanut conglutin and two modifications thereof were generated (RA and RAGA). Conglutin-specific T cell lines from 11 peanut-allergic patients were analysed for proliferation and cytokine production. Sera from 14 patients were analysed for IgE/IgG1/IgG4 binding by immunoblot and ELISA. IgE reactivity was analysed by direct and indirect basophil activation test (BAT), in presence and absence of patient plasma or CD32-blocking antibodies. T cell proliferation to RA was unchanged, and proliferation to RAGA was reduced compared to native conglutin. Cytokine profiles remained unchanged. IgE, IgG1 and IgG4 binding to RA and RAGA was significantly reduced. In the direct BAT, the relative potency of modified conglutin was decreased in 67% and increased/similar in 33% of the patients. In the indirect BAT, RA and RAGA were 10-100 times less potent than native conglutin. Addition of plasma to the indirect BAT increased the relative potency of modified conglutin in patients with high peanut-specific IgG levels. This was mediated via blocking of the response to native conglutin, most likely by soluble IgG, and not via CD32. Chemical modification of peanut conglutin by RA retains immunogenicity and reduces allergenicity and may be a promising approach for development of a curative treatment for peanut allergy. In a subgroup of patients, where the reactivity of native conglutin is already partially blocked by IgG, the effect of the modification of conglutin is less pronounced.

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HLA antibodies (Ab) activate endothelial cells (EC) and trigger monocyte (Mo) adhesion through P-selectin and FcγRs. FcγRIIa is dimorphic, at position H131R. We investigated whether FcγRIIa allotype or IgG subclass affect HLA I Ab-induced Mo adherence. Mo binding to immobilized or soluble IgG was measured by microscopy and flow cytometry, respectively. The variable regions of mouse anti-HLA I (W6/32) Ab were cloned onto human constant regions to generate chimerized HLA I hIgG1 and hIgG2. Human aortic EC were stimulated with murine or chimeric HLA I Ab and the number of adherent Mo was counted. H131 homozygous Mono Mac 6 (MM6) 1) did not bind mIgG1, 2) had enhanced capacity to bind hIgG2, and 3) bound hIgG1 through FcγRI and FcγRIIa. FcγRIIa-R131 homozygous U937 1) had enhanced capacity to bind mIgG1, 2) had reduced capacity to bind hIgG1 and mIgG2a, 3) did not bind hIgG2, and 4) bound hIgG1 through only FcγRI [Table 1]. HLA I mIgG1 and mIgG2a-activated EC recruited a comparable number of U937. FcγR inhibition significantly reduced adhesion of U937 to HLA I mIgG1 and mIgG2a-activated EC. In contrast, dramatically more MM6 were recruited in response to mIgG2a compared with mIgG1. FcγR blockade effectively inhibited adhesion of MM6 to HLA I mIgG2a, but not mIgG1, treated EC. Heterozygous THP-1 Mo displayed an intermediate phenotype. FcγR polymorphisms in DSA+ transplant patients may influence outcome. Recipients with FcγRIIa-H131 allele may experience greater infiltration of FcγR-bearing myeloid cells during AMR. DSA of the IgG2 subclass, while not complement fixing, may be clinically significant in H131 homozygous patients. Thus, strategies such as IVIG which reduce interaction of HLA I IgG with FcγRs are likely to diminish macrophage, neutrophil and NK trafficking to the graft.