Atypical Immune Response Research Articles

Platelet Metabolites as Candidate Biomarkers in Sepsis Diagnosis and Management Using the Proposed Explainable Artificial Intelligence Approach.

Background: Sepsis is characterized by an atypical immune response to infection and is a dangerous health problem leading to significant mortality. Current diagnostic methods exhibit insufficient sensitivity and specificity and require the discovery of precise biomarkers for the early diagnosis and treatment of sepsis. Platelets, known for their hemostatic abilities, also play an important role in immunological responses. This study aims to develop a model integrating machine learning and explainable artificial intelligence (XAI) to identify novel platelet metabolomics markers of sepsis. Methods: A total of 39 participants, 25 diagnosed with sepsis and 14 control subjects, were included in the study. The profiles of platelet metabolites were analyzed using quantitative 1H-nuclear magnetic resonance (NMR) technology. Data were processed using the synthetic minority oversampling method (SMOTE)-Tomek to address the issue of class imbalance. In addition, missing data were filled using a technique based on random forests. Three machine learning models, namely extreme gradient boosting (XGBoost), light gradient boosting machine (LightGBM), and kernel tree boosting (KTBoost), were used for sepsis prediction. The models were validated using cross-validation. Clinical annotations of the optimal sepsis prediction model were analyzed using SHapley Additive exPlanations (SHAP), an XAI technique. Results: The results showed that the KTBoost model (0.900 accuracy and 0.943 AUC) achieved better performance than the other models in sepsis diagnosis. SHAP results revealed that metabolites such as carnitine, glutamate, and myo-inositol are important biomarkers in sepsis prediction and intuitively explained the prediction decisions of the model. Conclusion: Platelet metabolites identified by the KTBoost model and XAI have significant potential for the early diagnosis and monitoring of sepsis and improving patient outcomes.

A term infant with severe hypereosinophilia secondary to CMV infection and the STAT1 gene mutation: a case report

Hypereosinophilia is a rare presentation in all age groups, particularly when it is severe, persistent, and progressive. We describe the clinical characteristics and course of severe hypereosinophilia in a full-term Saudi female neonate. A febrile respiratory illness evolved with a progressive increase in peripheral blood leukocyte and eosinophil counts, reaching 44.9% of leukocytes and an absolute value of 57,000 cells/µl. Different etiological examinations (for viral, bacterial, immunodeficiency, hyper IgE syndrome, gene mutations) revealed extremely high CMV antigenemia and a homozygous mutation in the STAT1 gene. Anhelation was relieved by oxygen and anti-viral treatment. Steroids brought a dramatic response in peripheral blood counts within 24 h. After a 6-week course of antiviral and steroid treatment at home, she had an excellent general condition. Conclusion: Although a rare pathology, it is important to consider genetic disorders when there is an atypical immune response to viral infections.

Individually or as a Team-The Immunological Milieu in the Lung Caused by Migrating Single-Sex or Mixed-Sex Larvae of Schistosoma mansoni.

While the lung is considered an efficient site for stopping the larvae of the acute Schistosoma spp. infection phase from migrating through extensive inflammatory responses in the surrounding tissues, little is known about these processes. To date, the highest resistance to infection has been achieved in experimental studies with radiation-attenuated cercariae immunization, which elicits a strong Th1/Th2 response in the lung and results in up to 80% protection. Based on our own studies demonstrating a systemic, unpolarized Th1/Th2 response resulting from infection with male or female Schistosoma mansoni, we hypothesize that this atypical immune response is already detectable during the pulmonary passage of parasite larvae. Therefore, we examined the immune milieu in the lungs of mice caused by migrating schistosome larvae, either male or female (single-sex groups) or male + female (bisexual control), 4 and 16 days after infection in bronchoalveolar lavage and lung tissue by flow cytometry, qPCR, and multiplex analyzes. Our results show only minor differences in the inflammatory profile between the single-sex groups but significant differences compared with the bisexual control group. Both single-sex infected groups have increased expression of inflammatory markers in lung tissue, higher numbers of cytotoxic T cells (day 4 post-infection) and more T helper cells (day 16 post-infection), compared with the bisexual control group. A single-sex infection, regardless of whether it is an infection with male or female cercariae, causes an immune milieu in the lung that is clearly different from an infection with both sexes. In terms of identifying therapeutic targets to achieve resistance to re-infection, it is of great scientific interest to identify the differences in the inflammatory potential of male or female and male + female parasites.

T‐cell population and PD‐1 expression in Alzheimer’s disease patients do not follow the age trend of normal individuals

AbstractBackgroundDestruction of cerebral neurons may relate to atypical immune responses. These intracerebral immune responses were induced by various antigens, such as viral DNA fragments or misfolded proteins. Aging is the major risk factor for Alzheimer’s disease (AD). Throughout the aging process, people experienced repetitive microbial infections and misfolded protein accumulation. But not every individual developed AD during aging. Immune regulation may contribute to determining whether the brain could clean unfavorable misfolded proteins and maintain homeostasis. T cell populations and programmed death 1 (PD‐1) are involved in immune pathology. In our study, we examined T cells and PD‐1 between normal aging and AD individuals to elucidate the role of immune regulation in aging‐related AD.MethodSixteen normal aging individuals (age range between 65‐91 years old) and 16 AD patients (age range 69‐88 years old) participated in this study. Peripheral blood mononuclear cells (PBMCs) were isolated from venous blood. Antibodies against T cells and PD‐1 molecules were used to classify PBMC with flow cytometry.Result(1) T cell population is different between normal and AD individualsThe normal aging group had significantly fewer adaptive immune T cells and fewer helper T cells (TH). However, these immune features were not present in AD patients.(2) PD‐1 pattern in PBMC is different between normal and AD individualsNatural killer T (NKT) cells with CD56 (neural cell adhesion molecule) had increased PD‐1 expression with normal aging. But AD patients did not show this trend of regulatory changes. These trends of suppressive phenotypic changes were absent in AD patients.ConclusionOur study demonstrated that the T‐cell population was shrinking progressively with normal aging. Nerve‐adherent NKT cells exhibited a higher inhibitory receptor (PD‐1). These findings suggested that T‐cell immune population tended to be suppressed with normal aging. However, these characteristic transitions of immune cells were not present in AD patients, suggesting that T cells were prone to activate in older AD patients. These distinctive immunomodulatory features of AD might be potential biomarkers of late‐onset AD, and predictive factors for developing AD in normal aging individuals.

SOCS-JAK-STAT inhibitors and SOCS mimetics as treatment options for autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis.

Autoimmune diseases arise from atypical immune responses that attack self-tissue epitopes, and their development is intricately connected to the disruption of the JAK-STAT signaling pathway, where SOCS proteins play crucial roles. Conditions such as autoimmune uveitis, psoriasis, lupus, and autoimmune encephalitis exhibit immune system dysfunctions associated with JAK-STAT signaling dysregulation. Emerging therapeutic strategies utilize JAK-STAT inhibitors and SOCS mimetics to modulate immune responses and alleviate autoimmune manifestations. Although more research and clinical studies are required to assess their effectiveness, safety profiles, and potential for personalized therapeutic approaches in autoimmune conditions, JAK-STAT inhibitors and SOCS mimetics show promise as potential treatment options. This review explores the action, effectiveness, safety profiles, and future prospects of JAK inhibitors and SOCS mimetics as therapeutic agents for psoriasis, autoimmune uveitis, systemic lupus erythematosus, and autoimmune encephalitis. The findings underscore the importance of investigating these targeted therapies to advance treatment options for individuals suffering from autoimmune diseases.

Recent advances in selective allergies to mammalian milk proteins not associated with Cow's Milk Proteins Allergy.

Cow's milk proteins allergy (CMA) is an atypical immune system response to cow's milk and dairy products. It's one of the most common food allergies in children affecting 8% of the total pediatric population pediatric population. This comprehensive review examines recent studies in CMA, especially regarding mammalian milk allergies such as goat's, sheep's, buffalo's, camel's, mare's and donkey's milk allergies in order to increase awareness of these selective allergies and to reduce allergy risks for those who have them. The consumption of other mammalian milk types is not recommended because of the significant homology between milk proteins from cow, sheep, goat and buffalo resulting in clinical cross-reactivity. However, camel's, mare's or donkey's milk may be tolerated by some allergic patients. Selective mammalian milk allergies are unusual and rare disorders characterized by severe symptoms including angio-oedema, urticaria, respiratory manifestations and anaphylaxis. Based on the reported allergic cases, cheese products including Ricotta, Romano, Pecorino and Mozzarella, are considered as the most common source of allergens especially in goat's, sheep's and buffalo's milk allergies, while the major allergens in donkey's and mare's milk seems to be whey proteins including lysozyme, α-lactalbumin and β-lactogloblin due to the low casein/whey proteins ratio in equine's milk.

Persistent but atypical germinal center reaction among 3rd SARS-CoV-2 vaccination after rituximab exposure.

BackgroundDurable vaccine-mediated immunity relies on the generation of long-lived plasma cells and memory B cells (MBCs), differentiating upon germinal center (GC) reactions. SARS-CoV-2 mRNA vaccination induces a strong GC response in healthy volunteers (HC), but limited data is available about response longevity upon rituximab treatment.MethodsWe evaluated humoral and cellular responses upon 3rd vaccination in seven patients with rheumatoid arthritis (RA) who initially mounted anti-spike SARS-CoV-2 IgG antibodies after primary 2x vaccination and got re-exposed to rituximab (RTX) 1-2 months after the second vaccination. Ten patients with RA on other therapies and ten HC represented the control groups. As control for known long-lived induced immunity, we analyzed humoral and cellular tetanus toxoid (TT) immune responses in steady-state.ResultsAfter 3rd vaccination, 5/7 seroconverted RTX patients revealed lower anti-SARS-CoV-2 IgG levels but similar neutralizing capacity compared with HC. Antibody levels after 3rd vaccination correlated with values after 2nd vaccination. Despite significant reduction of circulating total and antigen-specific B cells in RTX re-exposed patients, we observed the induction of IgG+ MBCs upon 3rd vaccination. Notably, only RTX treated patients revealed a high amount of IgA+ MBCs before and IgA+ plasmablasts after 3rd vaccination. IgA+ B cells were not part of the steady state TT+ B cell pool. TNF-secretion and generation of effector memory CD4 spike-specific T cells were significantly boosted upon 3rd vaccination.SummaryOn the basis of pre-existing affinity matured MBCs within primary immunisation, RTX re-exposed patients revealed a persistent but atypical GC immune response accompanied by boosted spike-specific memory CD4 T cells upon SARS-CoV-2 recall vaccination.

A Transcriptomic Study Reveals That Fish Vibriosis Due to the Zoonotic Pathogen Vibrio vulnificus Is an Acute Inflammatory Disease in Which Erythrocytes May Play an Important Role

Vibrio vulnificus is a marine zoonotic pathogen associated with fish farms that is considered a biomarker of climate change. Zoonotic strains trigger a rapid death of their susceptible hosts (fish or humans) by septicemia that has been linked to a cytokine storm in mice. Therefore, we hypothesize that V. vulnificus also causes fish death by triggering a cytokine storm in which red blood cells (RBCs), as nucleated cells in fish, could play an active role. To do it, we used the eel immersion infection model and then analyzed the transcriptome in RBCs, white BCs, and whole blood using an eel-specific microarray platform. Our results demonstrate that V. vulnificus triggers an acute but atypical inflammatory response that occurs in two main phases. The early phase (3 h post-infection [hpi]) is characterized by the upregulation of several genes for proinflammatory cytokines related to the mucosal immune response (il17a/f1 and il20) along with genes for antiviral cytokines (il12β) and antiviral factors (ifna and ifnc). In contrast, the late phase (12 hpi) is based on the upregulation of genes for typical inflammatory cytokines (il1β), endothelial destruction (mmp9 and hyal2), and, interestingly, genes related to an RNA-based immune response (sidt1). Functional assays revealed significant proteolytic and hemolytic activity in serum at 12 hpi that would explain the hemorrhages characteristic of this septicemia in fish. As expected, we found evidence that RBCs are transcriptionally active and contribute to this atypical immune response, especially in the short term. Based on a selected set of marker genes, we propose here an in vivo RT-qPCR assay that allows detection of early sepsis caused by V. vulnificus. Finally, we develop a model of sepsis that could serve as a basis for understanding sepsis caused by V. vulnificus not only in fish but also in humans.

SARS-CoV-2 Vaccine Induced Atypical Immune Responses in Antibody Defects: Everybody Does their Best

BackgroundData on immune responses to SARS-CoV-2 in patients with Primary Antibody Deficiencies (PAD) are limited to infected patients and to heterogeneous cohorts after immunization.MethodsForty-one patients with Common Variable Immune Deficiencies (CVID), six patients with X-linked Agammaglobulinemia (XLA), and 28 healthy age-matched controls (HD) were analyzed for anti-Spike and anti-receptor binding domain (RBD) antibody production, generation of Spike-specific memory B-cells, and Spike-specific T-cells before vaccination and one week after the second dose of BNT162b2 vaccine.ResultsThe vaccine induced Spike-specific IgG and IgA antibody responses in all HD and in 20% of SARS-CoV-2 naive CVID patients. Anti-Spike IgG were detectable before vaccination in 4 out 7 CVID previously infected with SARS-CoV-2 and were boosted in six out of seven patients by the subsequent immunization raising higher levels than patients naïve to infection. While HD generated Spike-specific memory B-cells, and RBD-specific B-cells, CVID generated Spike-specific atypical B-cells, while RBD-specific B-cells were undetectable in all patients, indicating the incapability to generate this new specificity. Specific T-cell responses were evident in all HD and defective in 30% of CVID. All but one patient with XLA responded by specific T-cell only.ConclusionIn PAD patients, early atypical immune responses after BNT162b2 immunization occurred, possibly by extra-follicular or incomplete germinal center reactions. If these responses to vaccination might result in a partial protection from infection or reinfection is now unknown. Our data suggests that SARS-CoV-2 infection more effectively primes the immune response than the immunization alone, possibly suggesting the need for a third vaccine dose for patients not previously infected.

Bacterial rhamnolipids and their 3-hydroxyalkanoate precursors activate Arabidopsis innate immunity through two independent mechanisms

Plant innate immunity is activated upon perception of invasion pattern molecules by plant cell-surface immune receptors. Several bacteria of the genera Pseudomonas and Burkholderia produce rhamnolipids (RLs) from l-rhamnose and (R)-3-hydroxyalkanoate precursors (HAAs). RL and HAA secretion is required to modulate bacterial surface motility, biofilm development, and thus successful colonization of hosts. Here, we show that the lipidic secretome from the opportunistic pathogen Pseudomonas aeruginosa, mainly comprising RLs and HAAs, stimulates Arabidopsis immunity. We demonstrate that HAAs are sensed by the bulb-type lectin receptor kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION/S-DOMAIN-1-29 (LORE/SD1-29), which also mediates medium-chain 3-hydroxy fatty acid (mc-3-OH-FA) perception, in the plant Arabidopsis thaliana HAA sensing induces canonical immune signaling and local resistance to plant pathogenic Pseudomonas infection. By contrast, RLs trigger an atypical immune response and resistance to Pseudomonas infection independent of LORE. Thus, the glycosyl moieties of RLs, although abolishing sensing by LORE, do not impair their ability to trigger plant defense. Moreover, our results show that the immune response triggered by RLs is affected by the sphingolipid composition of the plasma membrane. In conclusion, RLs and their precursors released by bacteria can both be perceived by plants but through distinct mechanisms.

Atypical immune response to Epstein-Barr virus in major depressive disorder

Background: An atypical immune response to Epstein-Barr virus (EBV) infection has been associated with several complex diseases including schizophrenia. The etiology of MDD is unclear; host immune response to EBV infection could play a role. Methods: We utilized solid phase immunoassays and western blots to measure antibodies to EBV virions, specific viral proteins, and 5 other herpesviruses in 87 individuals with MDD and 312 control individuals. Results: Individuals with MDD had significantly reduced levels of reactivity to EBV Nuclear Antigen-1. Quantitative levels of antibodies to EBV virions and Viral Capsid Antigen did not differ between groups. Individuals with decreased levels of anti-Nuclear Antigen-1, or elevated levels of anti-virion had increased odds of being in the MDD group. The odds of MDD were elevated in individuals who had the combination of high levels of anti-virion and low levels of anti-Nuclear Antigen-1 (OR =13.6). Western blot analysis corroborated decreased reactivity to Nuclear Antigen-1 in the MDD group and revealed altered levels of antibodies to other EBV proteins. There was a trend towards decreased levels of antibodies to varicella virus in the group of individuals with MDD. Limitations: The MDD sample size was relatively small. There could be unmeasured factors that account for the association between MDD and the immune response to EBV. Conclusions: Individuals with MDD have altered levels and patterns of antibodies to EBV antigens. This atypical response could contribute to the immunopathology of MDD. Therapeutic interventions available for treatment of EBV infection could potentially be of benefit in MDD.

Review of Clinical Studies Targeting Inflammatory Pathways for Individuals With Autism.

Immune dysfunction and abnormal immune response may be associated with certain mechanisms underlying autism spectrum disorder (ASD). The early evidence for this link was based on the increased incidence of ASD in children with a history of maternal infection during pregnancy. Observational studies show increased prevalence of immune-related disorders—ranging from atopy, food allergy, viral infections, asthma, primary immunodeficiency, to autoimmune disorders—in individuals with ASD and their families. Evidence of neuroglial activation and focal brain inflammation in individuals with ASD implies that the central nervous system immunity may also be atypical in some individuals with ASD. Also, both peripheral and central inflammatory responses are suggested to be associated with ASD-related behavioral symptoms. Atypical immune responses may be evident in specific ASD subgroups, such as those with significant gastrointestinal symptoms. The present review aimed to evaluate current literature of potential interventions that target inflammatory pathways for individuals with ASD and to summarize whether these interventions were associated with improvement in autism symptoms and adaptation. We found that the current literature on the efficacy of anti-inflammatory interventions in ASD is still limited and large-scale randomized controlled trials are needed to provide robust evidence. We concluded that the role of immune-mediated mechanisms in the emergence of ASD or related challenges may be specific to subsets of individuals (e.g. those with concurrent immunological disorders, developmental regression, or high irritability). These subsets of individuals of ASD might be more likely to benefit from interventions that target immune-mediated mechanisms and with whom next-stage immune-mediated clinical trials could be conducted.

Dendritic Cells Generated From Mops condylurus, a Likely Filovirus Reservoir Host, Are Susceptible to and Activated by Zaire Ebolavirus Infection.

Ebola virus infection of human dendritic cells (DCs) induces atypical adaptive immune responses and thereby exacerbates Ebola virus disease (EVD). Human DCs, infected with Ebola virus aberrantly express low levels of the DC activation markers CD80, CD86, and MHC class II. The T cell responses ensuing are commonly anergic rather than protective against EVD. We hypothesize that DCs derived from potential reservoir hosts such as bats, which do not develop disease signs in response to Ebola virus infection, would exhibit features associated with activation. In this study, we have examined Zaire ebolavirus (EBOV) infection of DCs derived from the Angolan free-tailed bat species, Mops condylurus. This species was previously identified as permissive to EBOV infection in vivo, in the absence of disease signs. M. condylurus has also been recently implicated as the reservoir host for Bombali ebolavirus, a virus species that is closely related to EBOV. Due to the absence of pre-existing M. condylurus species-specific reagents, we characterized its de novo assembled transcriptome and defined its phylogenetic similarity to other mammals, which enabled the identification of cross-reactive reagents for M. condylurus bone marrow-derived DC (bat-BMDC) differentiation and immune cell phenotyping. Our results reveal that bat-BMDCs are susceptible to EBOV infection as determined by detection of EBOV specific viral RNA (vRNA). vRNA increased significantly 72 h after EBOV-infection and was detected in both cells and in culture supernatants. Bat-BMDC infection was further confirmed by the observation of GFP expression in DC cultures infected with a recombinant GFP-EBOV. Bat-BMDCs upregulated CD80 and chemokine ligand 3 (CCL3) transcripts in response to EBOV infection, which positively correlated with the expression levels of EBOV vRNA. In contrast to the aberrant responses to EBOV infection that are typical for human-DC, our findings from bat-BMDCs provide evidence for an immunological basis of asymptomatic EBOV infection outcomes.

ERAP1 allotypes shape the epitope repertoire of virus-specific CD8+ T cell responses in acute hepatitis C virus infection

Endoplasmic reticulum aminopeptidase 1 (ERAP1) polymorphisms are linked with human leukocyte antigen (HLA) class I-associated autoinflammatory disorders, including ankylosing spondylitis and Behçet's disease. Disease-associated ERAP1 allotypes exhibit distinct functional properties, but it remains unclear how differential peptide trimming in vivo affects the repertoire of epitopes presented to CD8+ T cells. The aim of this study was to determine the impact of ERAP1 allotypes on the virus-specific CD8+ T cell epitope repertoire in an HLA-B*27:05+ individual with acute hepatitis C virus (HCV) infection. We performed genetic and functional analyses of ERAP1 allotypes and characterized the HCV-specific CD8+ T cell repertoire at the level of fine epitope specificity and HLA class I restriction, in a patient who had acquired an HCV genotype 1a infection through a needle-stick injury. Two hypoactive allotypic variants of ERAP1 were identified in an individual with acute HCV infection. The associated repertoire of virus-derived epitopes recognized by CD8+ T cells was uncommon in a couple of respects. Firstly, reactivity was directed away from classically immunodominant epitopes, preferentially targeting either novel or subdominant epitopes. Secondly, reactivity was biased towards longer epitopes (10-11-mers). Despite the patient exhibiting favorable prognostic indicators, these atypical immune responses failed to clear the virus and the patient developed persistent low-level infection with HCV. ERAP1 allotypes modify the virus-specific CD8+ T cell epitope repertoire in vivo, leading to altered immunodominance patterns that may contribute to the failure of antiviral immunity after infection with HCV. Endoplasmic reticulum aminopeptidase 1 (ERAP1) plays a key role in antigen presentation. Genetic variants of ERAP1 (leading to distinct allotypes) are linked with specific autoinflammatory disorders, such as ankylosing spondylitis and Behçet's disease. We found that ERAP1 allotypes modified the repertoire of virus-specific CD8+ T cell epitopes in a patient with hepatitis C virus, leading to an altered pattern of immunodominance that may have contributed to the failure of antiviral immunity in this patient.

Blood cell count in antipsychotic-naive patients with non-affective psychosis.

Schizophrenia is a complex medical entity with a reduced life expectancy, mostly due to an increased prevalence of cardiovascular diseases compared to the general population. An unbalanced immune response and a pro-inflammatory state might underlie this process. In treated patients, abnormal white blood cell (WBC), lymphocyte and neutrophil count suggests atypical immune response related to clinical variables. We aimed to test the hypothesis that newly diagnosed naïve patients with non-affective psychosis would show abnormal blood cell count values after controlling for potential confounding factors compared to matched controls. Seventy-five patients were compared with 80 controls matched for age, gender, body mass index and smoking. Analyses were conducted before and after controlling for smoking. Patients and controls displayed similar mean values (×103 /μL [SD]) for WBC count 7.02 [2.2] vs 6.50 [1.7] (P = .159), neutrophil count 4.25 [1.8] vs 3.84 [1.3] (P = .110) and monocyte count 0.43 [0.2] vs 0.40 [0.1] (P = .326). After controlling for smoking, 38 non-smoking patients showed a higher WBC and neutrophil count compared with 49 matched controls. Respective means of 7.01 [2.2] vs 5.97 [1.4] (P = .011) for WBC and 4.24 [1.9] vs 3.51 [1.2] (P = .028) for neutrophil count. Monocyte count showed an increased mean value 0.43 [0.2] vs 0.36 [0.1] with a trend towards signification (P = .063). These results suggest that abnormal immune response is present before the effects of medication and other confounders had taken place. Increased immune parameters might underlie the high ratio of medical co-morbidities described in schizophrenia.

The unique immunological features of heparin‐induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a serious drug reaction that leads to a decrease in platelet count and a high risk of thrombosis. HIT patients produce pathogenic immunoglobulin G (IgG) antibodies that bind to complexes of platelet factor-4 (PF4) and heparin. HIT immune complexes crosslink Fc-receptors resulting in platelet and monocyte activation. These events lead to the release of procoagulant chemokines and tissue factor, which together create an intensely prothrombotic state. HIT represents an atypical immune response because it has features of both T cell-dependent and T cell-independent mechanisms. The disorder is characterized by newly formed anti-PF4/heparin IgG antibodies, which are characteristic of a T cell-dependent mechanism; however, re-exposure to heparin, months after HIT, does not lead to a memory response, which is consistent with a T cell-independent mechanism. In this review, we discuss the immunobiological events that can explain these features, including the role for T cell-dependent and T cell-independent mechanisms in HIT antibody generation, the immunogenic characteristics of the PF4/heparin antigen, and the concept of a temporary loss in immune regulation contributing to the onset of HIT. We also present a novel immunobiological model to explain the atypical immune response that is characteristic of HIT.

Optimizing the Microbiome and Immune System With Maternal Diet in Pregnancy and Lactation May Prevent Food Allergies in Infants

Breast milk contains a perfect blend of macronutrients, vitamins, minerals, and water. This supports a baby’s nutritional needs exclusively for the first 6 months and beyond when paired with solid foods. Human milk also provides a unique blend of hormones, growth factors, and protective nutrients that support healthy functioning of the body as it matures, especially the microbiome within the digestive system. As a direct carrier of beneficial microbes, breast milk contains growth factors, oligosaccharides, lactoferrin, and lysozymes, which support the microbiome and immune system. These components regulate host–microbe interactions and establish the innate and adaptive immune response within the body. When the infant’s gastrointestinal tract is adequately colonized with an intact mucosal barrier, oral tolerance to antigens and pathogens creates a strong immune defense, avoiding expression of disease and atypical immune responses. There are many perinatal factors that affect the bacterial composition of breast milk and the maternal/infant gastrointestinal tract such as maternal body mass index, mode of delivery, perinatal antibiotic use, formula supplementation, and inflammation. Dysbiosis contributes to an increased expression of immune-mediated and allergic disease states. The impact of perinatal factors cannot always be prevented. When alternatives are not available, medical nutrition therapy can be key in supporting a healthy microbiome as well as improving maternal and infant gut function to prevent or treat food sensitivities. This article aims to address the role of maternal diet in pregnancy and lactation through optimizing the microbiome and immune system and reducing the infant allergy risk.

Complexes of platelet factor 4 and heparin activate Toll‐like receptor 4

In some patients, the anticoagulant heparin elicits formation of antibodies that can cause the life and/or limb-threatening syndrome known as heparin-induced thrombocytopenia (HIT). HIT antibodies target complexes formed at specific molar ratios of heparin and platelet factor 4 (PF4). The unpredictable occurrence and the mechanism of this atypical immune response to PF4:heparin complexes are poorly understood. We investigated whether complexes formed at specific PF4:heparin ratios (PHRs) might resemble molecular patterns associated with host defense responses. We used an in vitro cytokine release assay to determine whether defined PHRs caused cytokine release from human whole blood. Lipopolysaccharide (LPS) was used as a positive assay control, and some experiments included antibodies to block Toll-like receptor 4 (TLR4). PF4:heparin complexes caused release of the biomarker interleukin 8 in whole blood, and the level of response varied with the stoichiometric ratio of PF4 to heparin. The profile of response to LPS and to PF4:heparin complexes varied among blood donors, and the interleukin 8 response to both LPS and PF4:heparin was inhibited by TLR4-blocking antibodies. Specific PF4-heparin complexes can elicit a TLR4-mediated response, suggesting that these complexes can mimic a pathogen-associated molecular pattern, and supporting the suggestion that the HIT immune response represents a misdirected host defense mechanism.

Influence of FcγRIIA H131R Polymorphism on the Risk of Thrombosis in HIT and Variable Effect of Normal IgG on Platelet Activation

Introduction. Heparin-induced thrombocytopenia (HIT) results from an atypical immune response to platelet factor 4/heparin complexes (PF4/H), with rapid synthesis of IgG antibodies that activate platelets via FcγRIIA receptors. HIT is associated with thrombotic complications occurring in about 50% of affected patients.Moreover, the response of platelets to anti-PF4/H IgG varies from one subject to another. This variability, partly explained by gene polymorphisms affecting FcγRIIA signaling (Rollin et al, Blood 2012), might also depend on variations in the binding of HIT antibodies to FcγRIIA receptors.Objective. The influence of FcγRIIA H131R polymorphism on the risk of HIT and thrombosis was investigated in parallel with the effect of normal IgG on the platelet response to HIT antibodies.Patients and Methods. A cohort of 89 patients with definite HIT (PF4-specific ELISA and serotonin release assay both positive) and two control groups with (Abpos ; n=160) or without (Abneg ; n=179) significant levels of PF4-specific antibodies after cardiac surgery were studied. Platelet aggregation tests (PAT) were performed in 59 healthy donors using HIT plasma samples or 5B9, a humanized chimeric monoclonal antibody specific to PF4/H complexes that we have recently developed which fully mimics the effects of human HIT antibodies. The influence of normal IgG and IgG subclasses on platelet aggregation was also evaluated according to the FcγRIIA H131R polymorphism. Finally, tissue factor mRNA levels and plasma phospholipid-dependent procoagulant activity were measured after addition of HIT antibodies and heparin in the whole blood collected from healthy donors with different FCGR2A genotypes.Results. Genotypes and allele frequencies were similar in the HIT patients and both Abneg and Abpos controls. However, interestingly, homozygous FcγRIIA 131RR subjects were more frequent among the HIT patients who had developed thrombotic complications compared to those without thrombosis (34.5% vs. 8.5%, respectively, p=0.008). The FcγRIIA 131RR genotype therefore appeared to increase the risk of thrombosis in HIT significantly (OR = 5.9; 95% CI 1.7-20). This association was not found in two other cohorts of patients who had developed ischemic stroke or venous thromboembolism in a medical context other than HIT, thus indicating that the impact of FcγRIIA H131R polymorphism on the risk of thrombosis was specific to HIT. PAT performed with platelet-rich plasma (PRP) showed that the lag time measured in response to 5B9 with heparin (5B9/H) was significantly longer with FcγRIIA 131HH platelets compared to RR platelets (p=0.03). Importantly, this variable platelet response to 5B9/H related to the FcγRIIA polymorphism was no longer detectable when PAT were performed with washed platelets, when the IgG fraction had been removed from the plasma, and when collagen was used as inducer. On the other hand, the addition of human polyvalent IgG to IgG-depleted PRP inhibited the aggregation induced by 5B9/H, but lower concentrations of IgG were required to achieve this effect in FcγRIIA 131HH subjects compared to RR donors. Importantly, this variable effect of normal IgG on platelet aggregation induced by HIT antibodies was shown to depend mainly on the IgG2 subclass, which binds to the H131 isoform more effectively, whereas IgG1 exerted a similar inhibitory effect in RR and HH homozygous donors. Finally, a stronger increase in TF mRNA levels was also evidenced in homozygous FcγRIIARR donors compared to homozygous FcγRIIAHH donors after incubation of 5B9 and heparin in whole blood. Moreover, this effect was associated with a greater relative shortening of plasma clotting time indicating that the release of procoagulant phospholipid microparticles was more pronounced in RR subjects in response to HIT antibodies (p=0.04).Conclusion. These results demonstrate that HIT patients homozygous for the FcγRIIA 131R allele have a higher risk of thrombosis, probably due to an increased cell activation induced by antibodies to PF4/H with a lower inhibitory effect of endogenous IgG, especially of the IgG2subclass. DisclosuresNo relevant conflicts of interest to declare.

Dasatinib promotes Th1-type responses in granzyme B expressing T-cells

Tyrosine kinase inhibitors (TKIs) have dramatically improved the outcome of chronic myeloid leukemia (CML). Besides inhibiting target kinases in leukemic cells, 2nd generation TKI dasatinib also inhibits off-targets in immune effector cells resulting in atypical immune responses in some patients. Dasatinib has been described to increase the proportion of late effector memory T-cells, however, to date no follow-up studies have been performed in first-line patients. In this study, we explored the functional properties of T-cells using primary samples from CML patients (n = 28) on TKI therapy. Granzyme B (GrB) was used as a marker for late phase antigen experienced CD4+ and CD8+ T-cells. Dasatinib treatment increased the numbers of both GrB expressing memory CD4+ and CD8+ T-cells when compared with healthy controls. Functionally, the GrB+CD4+ T-cells were highly active and differentiated into Th1-type T-cells capable of producing IFN-γ, which is important for tumor control. Similar kind of increase was not observed during imatinib or nilotinib therapy. These data support the dual mode of action of dasatinib: potent BCR-ABL1 inhibition in leukemic cells is accompanied by the enhancement of cellular immunity, which may have implications in the long-term control of leukemia.