The interaction between ischemia–reperfusion and immune responses in the kidney

Kidney ischemia–reperfusion injury (IRI) engages both the innate and adaptive immune responses. Cellular mediators of immunity, such as dendritic cells, neutrophils, macrophages, natural killer T, T, and B cells, contribute to the pathogenesis of renal injury after IRI. Postischemic kidneys express increased levels of adhesion molecules on endothelial cells and toll-like receptors on tubular epithelial cells. Soluble components of the immune system, such as complement activation proteins and cytokines, also participate in injury/repair of postischemic kidneys. Experimental studies on the immune response in kidney IRI have resulted in better understanding of the mechanisms underlying IRI and led to the discovery of novel therapeutic and diagnostic targets.     

Zebrafish mast cells possess an Fc?RI-like receptor and participate in innate and adaptive immune responses

We previously identified a zebrafish mast cell (MC) lineage and now aim to determine if these cells function analogously in innate and adaptive immunity like their mammalian counterparts. Intraperitoneal (IP) injection of compound 48/80 or live Aeromonas salmonicida resulted in significant MC degranulation evident histologically and by increased plasma tryptase compared with saline-injected controls (p = 0.0006, 0.005, respectively). Pre-treatment with ketotifen abrogated these responses (p = 0.0004, 0.005, respectively). Cross-reactivity was observed in zebrafish to anti-human high-affinity IgE receptor gamma (Fc?RIγ) and IgE heavy chain-directed antibodies. Whole mount in situ hybridization on 7-day embryos demonstrated co-localization of cpa5, a MC-specific marker, with myd88, a toll-like receptor adaptor, and zebrafish Fc?RI subunit homologs. Zebrafish injected IP with matched dinitrophenyl-sensitized mouse (anti-DNP) IgE and DNP-BSA or trinitrophenyl-sensitized mouse (anti-TNP) IgE and TNP-BSA demonstrated increased plasma tryptase compared with mismatched controls (p = 0.03, 0.010, respectively). These results confirm functional conservation and validate the zebrafish model as an in vivo screening tool for novel MC modulating agents.     

The “ins and outs” of complement-driven immune responses

The complement system represents an evolutionary old and critical component of innate immunity where it forms the first line of defense against invading pathogens. Originally described as a heat-labile fraction of the serum responsible for the opsonization and subsequent lytic killing of bacteria, work over the last century firmly established complement as a key mediator of the general inflammatory response but also as an acknowledged vital bridge between innate and adaptive immunity. However, recent studies particularly spanning the last decade have provided new insights into the novel modes and locations of complement activation and highlighted unexpected additional biological functions for this ancient system, for example, in regulating basic processes of the cell. In this review, we will cover the current knowledge about complement's established and novel roles in innate and adaptive immunity with a focus on the functional differences between serum circulating and intracellularly active complement and will describe and discuss the newly discovered cross-talks of complement with other cell effector systems particularly during T-cell induction and contraction.     

B- and T-cell immune responses elicited by the Comirnaty® COVID-19 vaccine in nursing-home residents

ObjectivesThe immunogenicity of the Comirnaty® vaccine against coronavirus disease 2019 (COVID-19) has not been adequately studied in elderly people with comorbidities. We assessed antibody and T-cell responses targeted to the S protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) following full vaccination in nursing-home residents.MethodsSixty nursing-home residents (44 female, age 53–100 years), of whom ten had previously been diagnosed with COVID-19, and 18 healthy controls (15 female, age 27–54 years) were recruited. Pre- and post-vaccination blood specimens were available for quantification of total antibodies binding the SARS-CoV-2 S protein and for enumeration of SARS-CoV-2 S-reactive IFN-γ CD4⁺ and CD8⁺ T cells by flow cytometry.ResultsThe seroconversion rate in (presumably) SARS-CoV-2-naïve nursing-home residents (41/43, 95.3%) was similar to that in controls (17/18, 94.4%). A booster effect was documented in post-vaccination samples of nursing-home residents with prior COVID-19. Plasma antibody levels were higher (p < 0.01) in recovered nursing-home residents (all 2500 IU/mL) than in individuals across the other two groups (median 1120 IU/mL in naïve nursing-home residents and 2211 IU/ml in controls). A large percentage of nursing-home residents had SARS-CoV-2 S-reactive IFN-γ CD8⁺ (naïve 31/49, 63.2%; recovered 8/10, 80%) or CD4⁺ T cells (naïve 35/49, 71.4%; recovered 7/10, 70%) at baseline, in contrast to healthy controls (3/17, 17.6% and 5/17, 29%, respectively). SARS-CoV-2 IFN-γ CD8⁺ and CD4⁺ T-cell responses were documented in 88% (15/17) and all control subjects after vaccination, respectively, but only in 65.5% (38/58) and 22.4% (13/58) of nursing-home residents. Overall, the median frequency of SARS-CoV-2 IFN-γ CD8⁺ and CD4⁺ T cells in nursing-home residents decreased in post-vaccination specimens, whereas it increased in controls.ConclusionThe Comirnaty COVID-19 vaccine elicits robust SARS-CoV-2 S antibody responses in nursing-home residents. Nevertheless, the rate and frequency of detectable SARS-CoV-2 IFN-γ T-cell responses after vaccination was lower in nursing-home residents than in controls.     

Altered peptide ligands of myelin basic protein (MBP87–99) conjugated to reduced mannan modulate immune responses in mice

Mutations of peptides to generate altered peptide ligands, capable of switching immune responses from T helper 1 (Th1) to T helper 2 (Th2), are promising candidates for the immunotherapy of autoimmune diseases such as multiple sclerosis (MS). We synthesized two mutant peptides from myelin basic protein 87–99 (MBP_87–99), an immunodominant peptide epitope identified in MS. Mutations of residues K⁹¹ and P⁹⁶, known to be critical T-cell receptor (TCR) contact sites, resulted in the mutant peptides [R⁹¹, A⁹⁶]MBP_87–99 and [A⁹¹, A⁹⁶]MBP_87–99. Immunization of mice with these altered peptide ligands emulsified in complete Freund’s adjuvant induced both interferon-γ (IFN-γ) and interleukin-4 (IL-4) responses compared with only IFN-γ responses induced to the native MBP_87–99 peptide. It was of interest that [R⁹¹, A⁹⁶]MBP_87–99 conjugated to reduced mannan induced 70% less IFN-γ compared with the native MBP_87–99 peptide. However, [A⁹¹, A⁹⁶]MBP_87–99 conjugated to reduced mannan did not induce IFN-γ-secreting T cells, but elicited very high levels of interleukin-4 (IL-4). Furthermore, antibodies generated to [A⁹¹, A⁹⁶]MBP_87–99 peptide conjugated to reduced mannan did not cross-react with the native MBP_87–99 peptide. By molecular modelling of the mutant peptides in complex with major histocompatibility complex (MHC) class II, I-A^s, novel interactions were noted. It is clear that the double-mutant peptide analogue [A⁹¹, A⁹⁶]MBP_87–99 conjugated to reduced mannan is able to divert immune responses from Th1 to Th2 and is a promising mutant peptide analogue for use in studies investigating potential treatments for MS.     

SNPs in toll-like receptor (TLR) genes as new genetic alterations associated with congenital toxoplasmosis?

Nearly 40 % of pregnant women are infected with Toxoplasma gondii. Primary infections in pregnant women result, in approximately 30–50 % of patients, in transmission of T. gondii through the placenta to the fetus and then in congenital infections with severe, sometimes fatal course. Studies still do not provide sufficient data on the genetic bases of the immunity in fetuses, newborns, and infants with congenital toxoplasmosis. Previous research showed the contribution of toll-like receptors (TLRs) to non-specific immunity against T. gondii invasion, observed in T. gondii-infected animals, especially mice. So far, the activity of TLRs in defense against T. gondii infections was observed particularly for TLR2, TLR4, and TLR9 molecules. Differential TLR activity associates with both cell types, including a variety of placental cells and stage of pregnancy. Several single-nucleotide polymorphisms (SNPs) residing in three genes encoding these receptors were reported as significant genetic modifications of TLRs associated with different pregnancy disorders. Despite those data, genetic alterations of TLRs which have contributed to innate immune response against T. gondii infections are still not precisely described. In this article, we present reasons for the research of the plausible role of SNPs residing in TLR2, TLR4, and TLR9 genes in congenital toxoplasmosis development.     

Mycoplasma bovis-derived lipid-associated membrane proteins activate IL-1β production through the NF-κB pathway via toll-like receptor 2 and MyD88

Mycoplasma bovis causes pneumonia, otitis media, and arthritis in young calves, resulting in economic losses to the cattle industry worldwide. M. bovis pathogenesis results in part from excessive immune responses. Lipid-associated membrane proteins (LAMPs) can potently induce host innate immunity. However, interactions between M. bovis-derived LAMPs and Toll-like receptors (TLRs), or signaling pathways eliciting active inflammation and NF-κB activation, are incompletely understood. Here, we found that IL-1β expression was induced in embryonic bovine lung (EBL) cells stimulated with M. bovis-derived LAMPs. Subcellular-localization analysis revealed nuclear p65 translocation following EBL cell stimulation with M. bovis-derived LAMPs. An NF-κB inhibitor reversed M. bovis-derived LAMP-induced IL-1β expression. TLR2 and myeloid differentiation primary response gene 88 (MyD88) overexpression increased LAMP-dependent IL-1β induction. TLR2-neutralizing antibodies reduced IL-1β expression during LAMP stimulation. LAMPs also inhibited IL-1β expression following overexpression of a dominant-negative MyD88 protein. These results suggested that M. bovis-derived LAMPs activate IL-1β production through the NF-κB pathway via TLR2 and MyD88.     

A new therapeutic strategy to control HIV? The PD1 molecule and its role in inhibiting cellular immune responses

CD8+ T cells are crucial in protecting against viral infections by secreting antiviral factors and lysing infected cells. The loss of these functions is a hallmark of various chronic viral infections. In HIV chronic infection, CD8+ T cells develop this exhausted phenotype and their protection capacities diminish. Recently, it has been shown that a co-inhibitory molecule called PD-1 plays an important role on this exhausted phenotype. These findings open up the possibility of research targeted to develop therapeutic interventions that may restore CD8+ T cell function in chronic HIV infection.     

Agonistic autoantibodies to the α(1) -adrenergic receptor and the β(2) -adrenergic receptor in Alzheimer's and vascular dementia

Although primary causes of Alzheimer's and vascular dementia are unknown, the importance of preceding vascular lesions is widely accepted. Furthermore, there is strong evidence for the involvement of autoimmune mechanisms. Here, we report the presence of agonistic autoantibodies directed at adrenergic receptors in the circulation of patients with mild to moderate Alzheimer's and vascular dementia. In 59% of these patients, agonistic autoantibodies against the α(1) -adrenergic receptor and the β(2) -adrenergic receptor were identified. The majority of positive patients (66%) contained both types of autoantibodies in combination. In a control group of patients with neurological impairments others than Alzheimer's and vascular dementia, only 17% were found to harbour these autoantibodies. The autoantibodies to the α(1) -adrenergic receptor interacted preferably with the extracellular loop1 of the receptor. They were further studied in IgG preparations from the column regenerate of a patient who underwent immunoadsorption. The α(1) -adrenergic receptor autoantibodies specifically bound to the extracellular loop1 peptide of the receptor with an apparent EC(50) value of 30 nm. They mobilized intracellular calcium in a clonal cell line expressing the human form of the α(1) -adrenergic receptor. Our data support the notion that autoimmune mechanisms play a significant role in the pathogenesis of Alzheimer's and vascular dementia. We suggest that agonistic autoantibodies to the α(1) -adrenergic and the β(2) -adrenergic receptor may contribute to vascular lesions and increased plaque formation.     

Need for cellular and humoral immune responses in bovines to ensure protection from foot-and-mouth disease virus (FMDV)—A point of view

The published studies on immunization of experimental animals, cattle, and sheep with synthetic peptides containing the antigenic domains in FMDV structural protein VP1 were analyzed. The results obtained with various FMDV synthetic peptides designed to stimulate the humoral immune response in bovines were compared to the current knowledge on MHC class I and class II, and the properties of the peptide binding grooves in each of them. X-ray crystallography of MHC class I proteins provided the three-dimensional structure of the peptide binding groove and led to the isolation and identification of self and viral peptides that naturally associate with the peptide binding grooves of both types of MHC and HLA molecules. The available knowledge of the amino acid motifs in MHC and HLA class I-bound viral peptides priming the CD8⁺ cytotoxic T cell responses must be coupled with the understanding of the three-dimensional structure of BoLA class I. This would aid in the development of an experimental approach to induce bovine anti-FMDV CD8⁺ cytotoxic cells to complement the humoral immune response to FMDV, which is currently achieved by a killed virus vaccine and, at the experimental level, by a peptide vaccine. Stimulation of both cellular and humoral immune responses against FMDV in cattle may reduce the risk of disease and virus shedding.     

The urokinase receptor (u-PAR)--a link between tumor cell dormancy and minimal residual disease in bone marrow?

Minimal residual disease (MRD) is hypothesized to be the major cause of tumor recurrence and metastasis even years and decades after primary cancer diagnosis and curative solid tumor resection. In these patients disseminated tumor cells reflecting MRD can be detected in the bone marrow years after treatment. It is to be assumed that genetic determinants and a complex interplay between the disseminated tumor cells and their microenvironment in the bone marrow are responsible for tumor cell dormancy and the final reactivation towards metastasis. The urokinase receptor (u-PAR), a critical regulator of invasion, intravasation, and metastasis, is found to be a key player in regulating the shift between single cell tumor dormancy and proliferation. This has mainly been attributed to a regulation by u-PAR of integrins, and the ability of the latter to propagate signals from fibronectin through the EGF-receptor, ERK, and p38 signaling. Interestingly, u-PAR is found in disseminated tumor cells in the bone marrow of solid cancer patients, and is associated with the expansion of these cells and clinical prognosis. Here we summarize and discuss findings on disseminated tumor cells in the bone marrow, MRD and the role of u-PAR in tumor biology, especially focusing on its specific role in providing a switch between tumor cell proliferation and dormancy. Finally, we discuss the hypothesis that u-PAR might be an essential molecule in bone marrow disseminated tumor cells for long-term survival during dormancy, and/or reactivation of their proliferation years after primary treatment.     

The antinociceptive and antihyperalgesic effect of tapentadol is partially retained in OPRM1 (μ-opioid receptor) knockout mice

Activation of the μ-opioid receptor (MOR) and noradrenaline reuptake inhibition (NRI) are well recognized as analgesic principles in acute and chronic pain indications. The novel analgesic tapentadol combines MOR agonism and NRI in a single molecule. The present study used OPRM1 (MOR) knockout (KO) mice to determine the relative contribution of MOR activation to tapentadol-induced analgesia in models of acute (nociceptive) and chronic (neuropathic) pain. Antinociceptive efficacy was inferred from paw withdrawal latencies on a 48 °C hot plate in naive animals. Antihyperalgesic efficacy was inferred from the number of nocifensive reactions in diabetic animals (streptozotocin-induced) and non-diabetic controls on a 50 °C hot plate. The effect of tapentadol (0.316–31.6 mg/kg IP) and the MOR agonist morphine (3–10 mg/kg IP) was determined in OPRM1 KO- and congenic wildtype mice. At baseline, diabetic OPRM1 KO mice showed reduced nocifensive reactions as compared to diabetic wildtype mice. In both pain models, morphine and tapentadol were effective in wildtype mice. In the KO mice, however, morphine failed to produce analgesia in either model. On the other hand, tapentadol still had clear effects, and when tested at a dose that was fully efficacious in wildtype mice, showed reduced but still significant antinociceptive efficacy in non-diabetic, and antihyperalgesic efficacy in diabetic OPRM1 KO mice. The remaining antinociceptive activity of tapentadol in OPRM1 KO mice was abolished by the α₂-adrenoceptor antagonist yohimbine. In OPRM1 wildtype mice, the antihyperalgesic effect of tapentadol was 10 times more potent in diabetic animals (ED₅₀ = 1.10 mg/kg) than its antinociceptive effect in naïve animals (ED₅₀ = 10.8 mg/kg). This study supports the conclusion that the analgesic effect of tapentadol is only partly due to the activation of MOR, both under acute and chronic pain conditions, and that the efficacy of tapentadol against acute and chronic pain is based on its combined mechanism of action.     

Cyclooxygenase 2, toll-like receptor 4 and interleukin 1β mRNA expression in atherosclerotic plaques of type 2 diabetic patients

Objectives and design

Inflammation has a prominent role in the development of atherosclerosis. Type 2 diabetes could contribute to atherosclerosis development by promoting inflammation. This status might accelerate changes in intrinsic vascular wall cells and favor plaque formation. Cyclooxygenase 2 (COX-2) is highly expressed in atherosclerotic plaques. COX-2 gene expression is promoted through activation of toll-like receptor 4 (TLR4) and pro-inflammatory cytokine interleukin 1β (IL1-β). Aim of this study is to investigate whether expression profiles of pro-inflammatory genes such as COX-2, TLR4 and IL1-β in atherosclerotic plaques are altered in type 2 diabetes (T2D).

Methods

Total RNA was isolated from plaques of atherosclerotic patients and expression of COX-2, TLR4, IL1-β analyzed using real-time PCR. Histological analysis was performed on sections of the plaque to establish the degree of instability.

Results

Statistically significant differences in mRNA expression of COX-2 and IL1-β were found in plaques of T2D compared with non-T2D patients. A multi-variable linear regression model suggests that COX-2 mRNA expression is affected by T2D pathology and IL1-β mRNA expression in atherosclerotic plaques.

Conclusions

Our results support the hypothesis that T2D pathology contributes in vivo to increase the inflammatory process associated with the atherosclerotic plaque formation, as shown by an increment of COX-2 and IL1-β mRNA expression.     

Cellular immune responses in human immunodeficiency virus (HIV)-1-infected children: is immune restoration by highly active anti-retroviral therapy comparable to non-progression?

The objective of this study was to investigate whether the restored immune functions of vertically human immunodeficiency virus (HIV)-infected children who were severely immunodeficient before the initiation of highly active anti-retroviral therapy (HAART) are comparable to those of untreated slow progressors. We therefore assessed T cell proliferation and cytokine [interferon (IFN)-γ, interleukin (IL)-5 and IL-13] secretions after mitogen, recall antigens and HIV-1-specific stimulation in 12 untreated slow progressors, 16 untreated progressors and 18 treated patients. Treated children were profoundly immunodeficient before the initiation of HAART and had long-lasting suppression of viral replication on treatment. We demonstrated that slow progressors are characterized not only by the preservation of HIV-1-specific lymphoproliferative responses but also by the fact that these responses are clearly T helper type 1 (Th1)-polarized. Children on HAART had proliferative responses to HIV-1 p24 antigen, purified protein derivative (PPD) and tetanus antigen similar to slow progressors and higher than those of progressors. However, in contrast to slow progressors, most treated children exhibited a release of Th2 cytokines accompanying the IFN-γ secretion in response to the HIV-1 p24 antigen. Moreover, despite higher proliferative responses to phytohaemagglutinin (PHA) than the two groups of untreated children, treated children had lower levels of IFN-γ secretion in response to PHA than slow progressors. These data show that in severely immunodeficient vertically HIV-infected children, a long-lasting HAART allows recovering lymphoproliferative responses similar to untreated slow progressors. However, alterations in IFN-γ secretion in response to the mitogen PHA persisted, and their cytokine release after HIV-specific stimulation was biased towards a Th2 response.     

Receptor for AGE (RAGE) and its ligands—cast into leading roles in diabetes and the inflammatory response

The actors in the pathogenesis of diabetes and its complications are many and multifaceted. The effects of elevated levels of glucose are myriad; among these is the generation of advanced glycation end products (AGEs), the products of nonenzymatic glycoxidation of proteins and lipids. The finding that AGEs stimulate signal transduction cascades through the multiligand receptor RAGE unveiled novel insights into diabetes and its complications. Inextricably woven into AGE–RAGE interactions in diabetes is the engagement of the innate and adaptive immune responses. Although glucose may be the triggering stimulus to draw RAGE into diabetes pathology, consequent cellular stress results in release of proinflammatory RAGE ligands S100/calgranulins and HMGB1. We predict that once RAGE is engaged in the diabetic tissue, a vicious cycle of ligand–RAGE perturbation ensues, leading to chronic tissue injury and suppression of repair mechanisms. Targeting RAGE may be a beneficial strategy in diabetes, its complications, and untoward inflammatory responses.