The complement receptor 3, CR3 (CD11b/CD18), on T lymphocytes: activation-dependent up-regulation and regulatory function

CD4+ CD11b+ T cells infiltrate and aggravate the traumatic brain injury depending on brain-to-cervical lymph node signaling

AIM

We aim to identify the specific CD4+ T-cell subtype influenced by brain-to-CLN signaling and explore their role during the acute phase of traumatic brain injury (TBI).

METHOD

Cervical lymphadenectomy or cervical afferent lymphatic ligation was performed before TBI. Cytokine array and western blot were used to detect cytokines, while the motor function was assessed using mNss and rotarod test. CD4+ T-cell subtypes in blood, brain, and CLNs were analyzed with Cytometry by time-of-flight analysis (CyTOF) or fluorescence-activated cell sorting (FACS). Brain edema and volume changes were measured by 9.4T MRI. Neuronal apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining.

RESULTS

Cervical lymphadenectomy and ligation of cervical lymphatic vessels resulted in a decreased infiltration of CD4+ T cells, specifically CD11b-positive CD4+ T cells, within the affected region. The population of CD4+ CD11b+ T cells increased in ligated CLNs, accompanied by a decrease in the average fluorescence intensity of sphingosine-1-phosphate receptor-1 (S1PR1) on these cells. Administration of CD4+ CD11b+ T cells sorted from CLNs into the lateral ventricle reversed the attenuated neurologic deficits, brain edema, and lesion volume following cervical lymphadenectomy.

CONCLUSION

The infiltration of CD4+ CD11b+ T cells exacerbates secondary brain damage in TBI, and this process is modulated by brain-to-CLN signaling.

The Promise of Complement Therapeutics in Solid Organ Transplantation

Transplantation is the ideal therapy for end-stage organ failure, but outcomes for all transplant organs are suboptimal, underscoring the need to develop novel approaches to improve graft survival and function. The complement system, traditionally considered a component of innate immunity, is now known to broadly control inflammation and crucially contribute to induction and function of adaptive T-cell and B-cell immune responses, including those induced by alloantigens. Interest of pharmaceutical industries in complement therapeutics for nontransplant indications and the understanding that the complement system contributes to solid organ transplantation injury through multiple mechanisms raise the possibility that targeting specific complement components could improve transplant outcomes and patient health. Here, we provide an overview of complement biology and review the roles and mechanisms through which the complement system is pathogenically linked to solid organ transplant injury. We then discuss how this knowledge has been translated into novel therapeutic strategies to improve organ transplant outcomes and identify areas for future investigation. Although the clinical application of complement-targeted therapies in transplantation remains in its infancy, the increasing availability of new agents in this arena provides a rich environment for potentially transformative translational transplant research.

Complement factor H: a novel innate immune checkpoint in cancer immunotherapy

The elimination of cancer cells critically depends on the immune system. However, cancers have evolved a variety of defense mechanisms to evade immune monitoring, leading to tumor progression. Complement factor H (CFH), predominately known for its function in inhibiting the alternative pathway of the complement system, has recently been identified as an important innate immunological checkpoint in cancer. CFH-mediated immunosuppression enhances tumor cells' ability to avoid immune recognition and produce an immunosuppressive tumor microenvironment. This review explores the molecular underpinnings, interactions with immune cells, clinical consequences, and therapeutic possibilities of CFH as an innate immune checkpoint in cancer control. The difficulties and opportunities of using CFH as a target in cancer immunotherapy are also explored.

The Complement System in Kidney Transplantation

Kidney transplantation is the therapy of choice for patients who suffer from end-stage renal diseases. Despite improvements in surgical techniques and immunosuppressive treatments, long-term graft survival remains a challenge. A large body of evidence documented that the complement cascade, a part of the innate immune system, plays a crucial role in the deleterious inflammatory reactions that occur during the transplantation process, such as brain or cardiac death of the donor and ischaemia/reperfusion injury. In addition, the complement system also modulates the responses of T cells and B cells to alloantigens, thus playing a crucial role in cellular as well as humoral responses to the allograft, which lead to damage to the transplanted kidney. Since several drugs that are capable of inhibiting complement activation at various stages of the complement cascade are emerging and being developed, we will discuss how these novel therapies could have potential applications in ameliorating outcomes in kidney transplantations by preventing the deleterious effects of ischaemia/reperfusion injury, modulating the adaptive immune response, and treating antibody-mediated rejection.

C3-dependent effector functions of complement

C3 is the central effector molecule of the complement system, mediating its multiple functions through different binding sites and their corresponding receptors. We will introduce the C3 forms (native C3, C3 [H₂ O], and intracellular C3), the C3 fragments C3a, C3b, iC3b, and C3dg/C3d, and the C3 expression sites. To highlight the important role that C3 plays in human biological processes, we will give an overview of the diseases linked to C3 deficiency and to uncontrolled C3 activation. Next, we will present a structural description of C3 activation and of the C3 fragments generated by complement regulation. We will proceed by describing the C3a interaction with the anaphylatoxin receptor, followed by the interactions of opsonins (C3b, iC3b, and C3dg/C3d) with complement receptors, divided into two groups: receptors bearing complement regulatory functions and the effector receptors without complement regulatory activity. We outline the molecular architecture of the receptors, their binding sites on the C3 activation fragments, the cells expressing them, the diversity of their functions, and recent advances. With this review, we aim to give an up-to-date analysis of the processes triggered by C3 activation fragments on different cell types in health and disease contexts.

The Effect of Novel Selenopolysaccharide Isolated from Lentinula edodes Mycelium on Human T Lymphocytes Activation, Proliferation, and Cytokines Synthesis

Polysaccharides isolated from Lentinula edodes are bioactive compounds with immunomodulatory properties. In our previous studies from L. edodes mycelium, we have isolated a selenium(Se)-enriched fraction (named Se-Le-30), a mixture of linear 1,4-α-glucan and linear 1,3-β- and 1,6-β-glucans. In this study, we analyzed the effects of Se-Le-30 on the activation and proliferation of human T lymphocytes stimulated by anti-CD3 and anti-CD3/CD28 antibodies (Abs) and on the production of cytokines by peripheral blood mononuclear cells (PBMCs). Se-Le-30 had effects on T cell proliferation induced by Abs against CD3 and CD28. It significantly inhibited the proliferation of CD3-stimulated CD4⁺ and CD8⁺ T cells and enhanced the proliferation of CD4⁺ T cells stimulated with anti-CD3/CD28 Ab. Moreover, Se-Le-30 downregulated the number of CD3-stimulated CD4⁺CD69⁺ cells, CD4⁺CD25⁺ cells, as well as CD8⁺CD25⁺ cells, and upregulated the expression of CD25 marker on CD4+ and CD8+ T cells activated with anti-CD3/CD28 Abs. Furthermore, Se-Le-30 enhanced the synthesis of IFN-γ by the unstimulated and anti-CD3/CD28-stimulated PBMCs, inhibited synthesis of IL-2 and IL-4 by CD3-stimulated cells, and augmented the synthesis of IL-6 and IL-10 by unstimulated, CD3-stimulated, and CD3/CD28-stimulated PBMCs. Together, we demonstrated that Se-Le-30 exerts immunomodulatory effects on human T lymphocytes. These observations are of importance for the prospective use of Se-Le-30 in research or as a therapeutic compound.

Loss of CD11b Accelerates Lupus Nephritis in Lyn-Deficient Mice Without Disrupting Glomerular Leukocyte Trafficking

Systemic lupus erythematosus (SLE) is a complex, heterogeneous autoimmune disease. A common manifestation, lupus nephritis, arises from immune complex deposition in the kidney microvasculature promoting leukocyte activation and infiltration, which triggers glomerular damage and renal dysfunction. CD11b is a leukocyte integrin mainly expressed on myeloid cells, and aside from its well-ascribed roles in leukocyte trafficking and phagocytosis, it can also suppress cytokine production and autoreactivity. Genome-wide association studies have identified loss-of-function polymorphisms in the CD11b-encoding gene ITGAM that are strongly associated with SLE and lupus nephritis; however, it is not known whether these polymorphisms act alone to induce disease or in concert with other risk alleles. Herein we show using Itgam^-/- mice that loss of CD11b led to mild inflammatory traits, which were insufficient to trigger autoimmunity or glomerulonephritis. However, deficiency of CD11b in autoimmune-prone Lyn-deficient mice (Lyn^-/-Itgam^-/-) accelerated lupus-like disease, driving early-onset immune cell dysregulation, autoantibody production and glomerulonephritis, impacting survival. Migration of leukocytes to the kidney in Lyn^-/- mice was unhindered by lack of CD11b. Indeed, kidney inflammatory macrophages were further enriched, neutrophil retention in glomerular capillaries was increased and kidney inflammatory cytokine responses were enhanced in Lyn^-/-Itgam^-/- mice. These findings indicate that ITGAM is a non-monogenic autoimmune susceptibility gene, with loss of functional CD11b exacerbating disease without impeding glomerular leukocyte trafficking when in conjunction with other pre-disposing genetic mutations. This highlights a primarily protective role for CD11b in restraining inflammation and autoimmune disease and provides a potential therapeutic avenue for lupus treatment.

Role of Complement System in Kidney Transplantation: Stepping From Animal Models to Clinical Application

Kidney transplantation is a life-saving strategy for patients with end-stage renal diseases. Despite the advances in surgical techniques and immunosuppressive agents, the long-term graft survival remains a challenge. Growing evidence has shown that the complement system, part of the innate immune response, is involved in kidney transplantation. Novel insights highlighted the role of the locally produced and intracellular complement components in the development of inflammation and the alloreactive response in the kidney allograft. In the current review, we provide the updated understanding of the complement system in kidney transplantation. We will discuss the involvement of the different complement components in kidney ischemia-reperfusion injury, delayed graft function, allograft rejection, and chronic allograft injury. We will also introduce the existing and upcoming attempts to improve allograft outcomes in animal models and in the clinical setting by targeting the complement system.

Complement Factor H-Related 3 Enhanced Inflammation and Complement Activation in Human RPE Cells

Complement Factor H-Related 3 (FHR-3) is a major regulator of the complement system, which is associated with different diseases, such as age-related macular degeneration (AMD). However, the non-canonical local, cellular functions of FHR-3 remained poorly understood. Here, we report that FHR-3 bound to oxidative stress epitopes and competed with FH for interaction. Furthermore, FHR-3 was internalized by viable RPE cells and modulated time-dependently complement component (C3, FB) and receptor (C3aR, CR3) expression of human RPE cells. Independently of any external blood-derived proteins, complement activation products were detected. Anaphylatoxin C3a was visualized in treated cells and showed a translocation from the cytoplasm to the cell membrane after FHR-3 exposure. Subsequently, FHR-3 induced a RPE cell dependent pro-inflammatory microenvironment. Inflammasome NLRP3 activation and pro-inflammatory cytokine secretion of IL-1ß, IL-18, IL-6 and TNF-α were induced after FHR-3-RPE interaction. Our previously published monoclonal anti-FHR-3 antibody, which was chimerized to reduce immunogenicity, RETC-2-ximab, ameliorated the effect of FHR-3 on ARPE-19 cells. Our studies suggest FHR-3 as an exogenous trigger molecule for the RPE cell “complosome” and as a putative target for a therapeutic approach for associated degenerative diseases.

Insights Into the Structure-Function Relationships of Dimeric C3d Fragments

Cleavage of C3 to C3a and C3b plays a central role in the generation of complement-mediated defences. Although the thioester-mediated surface deposition of C3b has been well-studied, fluid phase dimers of C3 fragments remain largely unexplored. Here we show C3 cleavage results in the spontaneous formation of C3b dimers and present the first X-ray crystal structure of a disulphide-linked human C3d dimer. Binding studies reveal these dimers are capable of crosslinking complement receptor 2 and preliminary cell-based analyses suggest they could modulate B cell activation to influence tolerogenic pathways. Altogether, insights into the physiologically-relevant functions of C3d(g) dimers gained from our findings will pave the way to enhancing our understanding surrounding the importance of complement in the fluid phase and could inform the design of novel therapies for immune system disorders in the future.

New aspects in the regulation of human B cell functions by complement receptors CR1, CR2, CR3 and CR4

The involvement of complement in the regulation of antibody responses has been known for long. By now several additional B cell functions - including cytokine production and antigen presentation - have also been shown to be regulated by complement proteins. Most of these important activities are mediated by receptors interacting with activation fragments of the central component of the complement system C3, such as C3b, iC3b and C3d, which are covalently attached to antigens and immune complexes. This review summarizes the role of complement receptors interacting with these ligands, namely CR1 (CD35), CR2 (CD21), CR3 (CD11b/CD18) and CR4 (CD11c/CD18) expressed by B cells in health and disease. Although we focus on human B lymphocytes, we also aim to call the attention to important differences between human and mouse systems.

Polysaccharide from Codium fragile Induces Anti-Cancer Immunity by Activating Natural Killer Cells

Natural polysaccharides exhibit beneficial immune modulatory effects, including immune stimulatory and anti-cancer activities. In this study, we examined the effect of Codium fragile polysaccharide (CFP) on natural killer (NK) cell activation, and its effect on tumor-bearing mice. Intravenous CFP treatment of C57BL/6 mice resulted in the upregulation of CD69, which is a marker associated with NK cell activation. In addition, intracellular levels of interferon (IFN)-γ and the cytotoxic mediators perforin and granzyme B were markedly increased in response to the CFP treatment of splenic NK cells. IFN-γ production by NK cells was directly induced by CFP, whereas the upregulation of CD69 and cytotoxic mediators required IL-12. Finally, intraperitoneal treatment with CFP prevented CT-26 (murine carcinoma) tumor cell infiltration in the lungs, without significantly reducing the body weight. In addition, treatment with CFP prevented B16 melanoma cell infiltration in the lung of C57BL/6 mice. Moreover, the anti-tumor effect was diminished by the depletion of NK cells. Therefore, these data suggest that CFP may be used as an NK cell stimulator to produce a phenomenon that contributes to anti-cancer immunity.

Flow Cytometry-Detected Immunological Markers and on Farm Recorded Parameters in Composite Cow Milk as Related to Udder Health Status

Flow cytometry is a powerful technology used in many fields of cell biology. It is also used as a routine method to count somatic cells in milk and to characterize bovine milk leukocytes. In this study, we used flow cytometry to simultaneously assess the viability, the percentage of the single subsets of leukocytes and to quantify the expression of CD11b, an immunological marker of cell activation status. Immunological markers were then related with on farm recorded parameters as milk electrical conductivity (MEC) and average milk flow rate (MFR). Composite milk samples were collected from 43 cows, nine of which had naturally infected udders and 34 of which had no infected udders. First, the milk samples were classified according to bacteriological test in positive and negative. The results showed that the negative samples to bacteriological test had: (i) significantly higher percentages of live lymphocytes; (ii) significantly lower percentages of CD11b⁺ leukocytes; (iii) significantly lower MEC and higher MFR values. Then, samples were classified in three groups according to somatic cell count (SCC): Group A (n = 15), samples with SCC ≤ 100,000 cells/mL, all negative to bacteriological analysis; Group B (n = 11), samples with 100,000 < SCC < 300,000 cells/m, with four samples positive to bacteriological analysis; Group C (n = 17), samples with SCC ≥ 300,000 cell/mL with five samples positive to bacteriological analysis. Multivariate discriminant analysis was used to verify which flow cytometry immunological markers and on farm recorded parameters could better discriminate among the different groups of SCCs. Linear discriminant analysis (LDA) indicated that 5 of the 10 parameters could best be used to reveal the differences between positive and negative samples among the considered groups of SCCs. Furthermore, the Canonical discriminant analysis (CDA) indicated that composite milk samples with different SCC and infection status were clearly separated from each other in a two-dimensional space. In conclusion, the study highlighted that: (1) the conventional flow cytometry analysis applied on milk samples is a useful tool to investigate immunological parameters as potential indicators of udder health; (2) the combined evaluation of live milk leukocytes and recorded farm parameters could be useful to assess udder health status in dairy cows. The results obtained from this pilot study on few data require new and larger trials to be confirmed.

Diapedesis-Induced Integrin Signaling via LFA-1 Facilitates Tissue Immunity by Inducing Intrinsic Complement C3 Expression in Immune Cells

Intrinsic complement C3 activity is integral to human T helper type 1 (Th1) and cytotoxic T cell responses. Increased or decreased intracellular C3 results in autoimmunity and infections, respectively. The mechanisms regulating intracellular C3 expression remain undefined. We identified complement, including C3, as among the most significantly enriched biological pathway in tissue-occupying cells. We generated C3-reporter mice and confirmed that C3 expression was a defining feature of tissue-immune cells, including T cells and monocytes, occurred during transendothelial diapedesis, and depended on integrin lymphocyte-function-associated antigen 1 (LFA-1) signals. Immune cells from patients with leukocyte adhesion deficiency type 1 (LAD-1) had reduced C3 transcripts and diminished effector activities, which could be rescued proportionally by intracellular C3 provision. Conversely, increased C3 expression by T cells from arthritis patients correlated with disease severity. Our study defines integrins as key controllers of intracellular complement, demonstrates that perturbations in the LFA-1-C3-axis contribute to primary immunodeficiency, and identifies intracellular C3 as biomarker of severity in autoimmunity.

Amniotic fluid CD11b levels in pregnancies complicated by preterm prelabor rupture of membranes

Objective: CD11b is an integrin molecule located on the surface of leukocytes. CD11b is involved in the processes of cell adhesion and migration. Expression of CD11b increases during inflammation. Therefore, this study was aimed at the evaluation of concentrations of CD11b in the amniotic fluid from pregnancies complicated by preterm prelabor rupture of the membranes (PPROM), with respect to the presence of microbial invasion of the amniotic cavity (MIAC), intra-amniotic inflammation (IAI), and microbial-associated IAI (the presence of both MIAC and IAI).Methods: Eighty women with singleton pregnancies complicated by PPROM were included. Amniotic fluid samples were obtained by transabdominal amniocentesis. Amniotic fluid CD11b concentrations were determined by enzyme-linked immunosorbent assay. MIAC was determined by a non-cultivation approach. IAI was defined by a bedside amniotic fluid interleukin-6 concentration ≥745 pg/mL.Result: Women with MIAC or microbial-associated IAI had higher CD11b concentrations in the amniotic fluid than women without these complications (with MIAC: median 0.31 ng/mL versus without MIAC: median 0.17 ng/mL, p = .001; with microbial associated-IAI: median 0.35 ng/mL versus without microbial-associated IAI: median 0.16 ng/mL; p =.02). The presence of IAI was not associated with elevated CD11b concentrations. A weak negative correlation was found between amniotic fluid CD11b concentrations and interleukin-6 concentrations (rho = 0.26; p = .02).Conclusions: MIAC and microbial-associated IAI are characterized by higher amniotic fluid CD11b concentrations in pregnancies complicated by PPROM.

Retargeting from the CR3 to the LFA-1 receptor uncovers the adenylyl cyclase enzyme-translocating segment of Bordetella adenylate cyclase toxin

The Bordetella adenylate cyclase toxin-hemolysin (CyaA) and the α-hemolysin (HlyA) of Escherichia coli belong to the family of cytolytic pore-forming Repeats in ToXin (RTX) cytotoxins. HlyA preferentially binds the α_Lβ₂ integrin LFA-1 (CD11a/CD18) of leukocytes and can promiscuously bind and also permeabilize many other cells. CyaA bears an N-terminal adenylyl cyclase (AC) domain linked to a pore-forming RTX cytolysin (Hly) moiety, binds the complement receptor 3 (CR3, α_Mβ₂, CD11b/CD18, or Mac-1) of myeloid phagocytes, penetrates their plasma membrane, and delivers the AC enzyme into the cytosol. We constructed a set of CyaA/HlyA chimeras and show that the CyaC-acylated segment and the CR3-binding RTX domain of CyaA can be functionally replaced by the HlyC-acylated segment and the much shorter RTX domain of HlyA. Instead of binding CR3, a CyaA_1-710/HlyA_411-1024 chimera bound the LFA-1 receptor and effectively delivered AC into Jurkat T cells. At high chimera concentrations (25 nm), the interaction with LFA-1 was not required for CyaA_1-710/HlyA_411-1024 binding to CHO cells. However, interaction with the LFA-1 receptor strongly enhanced the specific capacity of the bound CyaA_1-710/HlyA_411-1024 chimera to penetrate cells and deliver the AC enzyme into their cytosol. Hence, interaction of the acylated segment and/or the RTX domain of HlyA with LFA-1 promoted a productive membrane interaction of the chimera. These results help delimit residues 400-710 of CyaA as an "AC translocon" sufficient for translocation of the AC polypeptide across the plasma membrane of target cells.

Complement: Bridging the innate and adaptive immune systems in sterile inflammation

The complement system is a collection of soluble and membrane-bound proteins that together act as a powerful amplifier of the innate and adaptive immune systems. Although its role in infection is well established, complement is becoming increasingly recognized as a key contributor to sterile inflammation, a chronic inflammatory process often associated with noncommunicable diseases. In this context, damaged tissues release danger signals and trigger complement, which acts on a range of leukocytes to augment and bridge the innate and adaptive immune systems. Given the detrimental effect of chronic inflammation, the complement system is therefore well placed as an anti-inflammatory drug target. In this review, we provide a general outline of the sterile activators, effectors, and targets of the complement system and a series of examples (i.e., hypertension, cancer, allograft transplant rejection, and neuroinflammation) that highlight complement's ability to bridge the 2 arms of the immune system.

Saccharomyces cerevisiae (YT001) supplementation for the control of Haemonchus contortus and modulation of the immune response of sheep

Studies aiming at the development and evaluation of alternative methods to minimise losses caused by the gastrointestinal nematode Haemonchus contortus are extremely important. Such research is essential, given the high morbidity rates among sheep and the significant mortality rates of lambs, allied to the low efficacy of commercial products for the control of this parasite. The purpose of this study was to evaluate the effect of the Saccharomyces cerevisiae (YT001 - YEASTECH) on the control of H. contortus and its modulation of the immune response in experimentally infected sheep. Eighteen sheep were divided into two groups. Group 1, the control group, comprised animals infected with H. contortus and supplemented with distilled water, while Group 2, the treated group, consisted of animals infected and supplemented with S. cerevisiae (400 million cfu/day of suspension for 49 days). The following parasitological parameters were evaluated: number of eggs per gram of faeces, number of infective larvae (L3) recovered per faecal culture, and parasitic load of the abomasum. The following immunological parameters were quantified: immunoglobulin (Ig)A in the mucous secretions and serum IgG; cytokines interleukin (IL)-4, IL-5 and IL-10; number of eosinophils in the abomasal mucosa and groups of cells positive for the markers: MHCII, CD4⁺CD25⁺, CD5⁺CD8⁺, WC4, CD5⁺CD4⁺, CD8⁺CD11b⁺ and CD5⁺WC1 by whole blood flow cytometry. The results revealed a significant decrease (P<0.05) in the number of larvae and significantly higher serum IgG levels (P<0.05) in the group supplemented with S. cerevisiae. The supplemented animals showed significantly larger numbers of eosinophils (P<0.05), as well as more cells positive for MHCII, CD4⁺CD25⁺, CD5⁺CD8⁺ than the control animals. This study confirmed the beneficial action of S. cerevisiae on the host immune response to H. contortus, as evidenced mainly by the smaller number of L3 recovered from the faeces of sheep supplemented with S. cerevisiae.

Astrocytic trans-Differentiation Completes a Multicellular Paracrine Feedback Loop Required for Medulloblastoma Tumor Growth

The tumor microenvironment (TME) is critical for tumor progression. However, the establishment and function of the TME remain obscure because of its complex cellular composition. Using a mouse genetic system called mosaic analysis with double markers (MADMs), we delineated TME evolution at single-cell resolution in sonic hedgehog (SHH)-activated medulloblastomas that originate from unipotent granule neuron progenitors in the brain. First, we found that astrocytes within the TME (TuAstrocytes) were trans-differentiated from tumor granule neuron precursors (GNPs), which normally never differentiate into astrocytes. Second, we identified that TME-derived IGF1 promotes tumor progression. Third, we uncovered that insulin-like growth factor 1 (IGF1) is produced by tumor-associated microglia in response to interleukin-4 (IL-4) stimulation. Finally, we found that IL-4 is secreted by TuAstrocytes. Collectively, our studies reveal an evolutionary process that produces a multi-lateral network within the TME of medulloblastoma: a fraction of tumor cells trans-differentiate into TuAstrocytes, which, in turn, produce IL-4 that stimulates microglia to produce IGF1 to promote tumor progression.

Structural Immunology of Complement Receptors 3 and 4

Complement receptors (CR) 3 and 4 belong to the family of beta-2 (CD18) integrins. CR3 and CR4 are often co-expressed in the myeloid subsets of leukocytes, but they are also found in NK cells and activated T and B lymphocytes. The heterodimeric ectodomain undergoes considerable conformational change in order to switch the receptor from a structurally bent, ligand-binding in-active state into an extended, ligand-binding active state. CR3 binds the C3d fragment of C3 in a way permitting CR2 also to bind concomitantly. This enables a hand-over of complement-opsonized antigens from the cell surface of CR3-expressing macrophages to the CR2-expressing B lymphocytes, in consequence acting as an antigen presentation mechanism. As a more enigmatic part of their functions, both CR3 and CR4 bind several structurally unrelated proteins, engineered peptides, and glycosaminoglycans. No consensus motif in the proteinaceous ligands has been established. Yet, the experimental evidence clearly suggest that the ligands are primarily, if not entirely, recognized by a single site within the receptors, namely the metal-ion dependent adhesion site (MIDAS). Comparison of some recent identified ligands points to CR3 as inclined to bind positively charged species, while CR4, by contrast, binds strongly negative-charged species, in both cases with the critical involvement of deprotonated, acidic groups as ligands for the Mg²⁺ ion in the MIDAS. These properties place CR3 and CR4 firmly within the realm of modern molecular medicine in several ways. The expression of CR3 and CR4 in NK cells was recently demonstrated to enable complement-dependent cell cytotoxicity toward antibody-coated cancer cells as part of biological therapy, constituting a significant part of the efficacy of such treatment. With the flexible principles of ligand recognition, it is also possible to propose a response of CR3 and CR4 to existing medicines thereby opening a possibility of drug repurposing to influence the function of these receptors. Here, from advances in the structural and cellular immunology of CR3 and CR4, we review insights on their biochemistry and functions in the immune system.

Complement After Trauma: Suturing Innate and Adaptive Immunity

The overpowering effect of trauma on the immune system is undisputed. Severe trauma is characterized by systemic cytokine generation, activation and dysregulation of systemic inflammatory response complementopathy and coagulopathy, has been immensely instrumental in understanding the underlying mechanisms of the innate immune system during systemic inflammation. The compartmentalized functions of the innate and adaptive immune systems are being gradually recognized as an overlapping, interactive and dynamic system of responsive elements. Nonetheless the current knowledge of the complement cascade and its interaction with adaptive immune response mediators and cells, including T- and B-cells, is limited. In this review, we discuss what is known about the bridging effects of the complement system on the adaptive immune system and which unexplored areas could be crucial in understanding how the complement and adaptive immune systems interact following trauma.

Integral Roles for Integrins in γδ T Cell Function

Integrins are adhesion receptors on the cell surface that enable cells to respond to their environment. Most integrins are heterodimers, comprising α and β type I transmembrane glycoprotein chains with large extracellular domains and short cytoplasmic tails. Integrins deliver signals through multiprotein complexes at the cell surface, which interact with cytoskeletal and signaling proteins to influence gene expression, cell proliferation, morphology, and migration. Integrin expression on γδ T cells (γδTc) has not been systematically investigated; however, reports in the literature dating back to the early 1990s reveal an understated role for integrins in γδTc function. Over the years, integrins have been investigated on resting and/or activated peripheral blood-derived polyclonal γδTc, γδTc clones, as well as γδ T intraepithelial lymphocytes. Differences in integrin expression have been found between αβ T cells (αβTc) and γδTc, as well as between Vδ1 and Vδ2 γδTc. While most studies have focused on human γδTc, research has also been carried out in mouse and bovine models. Roles attributed to γδTc integrins include adhesion, signaling, activation, migration, tissue localization, tissue retention, cell spreading, cytokine secretion, tumor infiltration, and involvement in tumor cell killing. This review attempts to encompass all reports of integrins expressed on γδTc published prior to December 2017, highlights areas warranting further investigation, and discusses the relevance of integrin expression for γδTc function.

Lymphocyte integration of complement cues

We address current data, views and puzzles on the emerging topic of regulation of lymphocytes by complement proteins or fragments. Such regulation is believed to take place through complement receptors (CR) and membrane complement regulators (CReg) involved in cell function or protection, respectively, including intracellular signalling. Original observations in B cells clearly support that complement cues through CR improve their performance. Other lymphocytes likely integrate complement-derived signals, as most lymphoid cells constitutively express or regulate CR and CReg upon activation. CR-induced signals, particularly by anaphylatoxins, clearly regulate lymphoid cell function. In contrast, data obtained by CReg crosslinking using antibodies are not always confirmed in human congenital deficiencies or knock-out mice, casting doubts on their physiological relevance. Unsurprisingly, human and mouse complement systems are not completely homologous, adding further complexity to our still fragmentary understanding of complement-lymphocyte interactions.

Non-identical twins: Different faces of CR3 and CR4 in myeloid and lymphoid cells of mice and men

Integrins are cell membrane receptors that are involved in essential physiological and serious pathological processes. Their main role is to ensure a closely regulated link between the extracellular matrix and the intracellular cytoskeletal network enabling cells to react to environmental stimuli. Complement receptor type 3 (CR3, αMβ₂, CD11b/CD18) and type 4 (CR4, αXβ₂, CD11c/CD18) are members of the β₂-integrin family expressed on most white blood cells. Both receptors bind multiple ligands like iC3b, ICAM, fibrinogen or LPS. β₂-integrins are accepted to play important roles in cellular adhesion, migration, phagocytosis, ECM rearrangement and inflammation. Several pathological conditions are linked to the impaired functions of these receptors. CR3 and CR4 are generally thought to mediate overlapping functions in monocytes, macrophages and dendritic cells, therefore the potential distinctive role of these receptors has not been investigated so far in satisfactory details. Lately it has become clear that a functional segregation has evolved between the two receptors regarding phagocytosis, cellular adhesion and podosome formation. In addition to their tasks on myeloid cells, the expression and function of CR3 and CR4 on lymphocytes have also gained interest recently. The picture is further complicated by the fact that while these β₂-integrins are expressed by immune cells both in mice and humans, there are significant differences in their expression level, functions and the pathological consequences of genetic defects. Here we aim to summarize our current knowledge on CR3 and CR4 and highlight the functional differences between these receptors, involving their expression in myeloid and lymphoid cells of both men and mice.

Prenatal alcohol exposure potentiates chronic neuropathic pain, spinal glial and immune cell activation and alters sciatic nerve and DRG cytokine levels

A growing body of evidence indicates that prenatal alcohol exposure (PAE) may predispose individuals to secondary medical disabilities later in life. Animal models of PAE reveal neuroimmune sequelae such as elevated brain astrocyte and microglial activation with corresponding region-specific changes in immune signaling molecules such as cytokines and chemokines. The aim of this study was to evaluate the effects of moderate PAE on the development and maintenance of allodynia induced by chronic constriction injury (CCI) of the sciatic nerve in adult male rat offspring. Because CCI allodynia requires the actions of glial cytokines, we analyzed lumbar spinal cord glial and immune cell surface markers indicative of their activation levels, as well as sciatic nerve and dorsal root ganglia (DRG) cytokines in PAE offspring in adulthood. While PAE did not alter basal sensory thresholds before or after sham manipulations, PAE significantly potentiated adult onset and maintenance of allodynia. Microscopic analysis revealed exaggerated astrocyte and microglial activation, while flow cytometry data demonstrated increased proportions of immune cells with cell surface major histocompatibility complex II (MHCII) and β-integrin adhesion molecules, which are indicative of PAE-induced immune cell activation. Sciatic nerves from CCI rats revealed that PAE potentiated the proinflammatory cytokines interleukin (IL)-1β, IL-6 and tumor necrosis factor-alpha (TNFα) protein levels with a simultaneous robust suppression of the anti-inflammatory cytokine, IL-10. A profound reduction in IL-10 expression in the DRG of PAE neuropathic rats was also observed. Taken together, our results provide novel insights into the vulnerability that PAE produces for adult-onset central nervous system (CNS) pathological conditions from peripheral nerve injury.

Prophylactic orthosteric inhibition of leukocyte integrin CD11b/CD18 prevents long-term fibrotic kidney failure in cynomolgus monkeys

Ischaemic acute kidney injury (AKI), an inflammatory disease process, often progresses to chronic kidney disease (CKD), with no available effective prophylaxis. This is in part due to lack of clinically relevant CKD models in non-human primates. Here we demonstrate that inhibition of the archetypal innate immune receptor CD11b/CD18 prevents progression of AKI to CKD in cynomolgus monkeys. Severe ischaemia-reperfusion injury of the right kidney, with subsequent periods of the left ureter ligation, causes irreversible right kidney failure 3, 6 or 9 months after AKI. Moreover, prophylactic inactivation of CD11b/CD18, using the orthosteric CD11b/CD18 inhibitor mAb107, improves microvascular perfusion and histopathology, reduces intrarenal pro-inflammatory mediators and salvages kidney function long term. These studies reveal an important early role of CD11b⁺ leukocytes in post-ischaemic kidney fibrosis and failure, and suggest a potential early therapeutic intervention to mitigate progression of ischaemic AKI to CKD in humans.

Biology and structure of leukocyte β 2 integrins and their role in inflammation

Integrins comprise a large family of αβ heterodimeric cell adhesion receptors that are expressed on all cells except red blood cells and that play essential roles in the regulation of cell growth and function. The leukocyte integrins, which include members of the β ₁, β ₂, β ₃, and β ₇ integrin family, are critical for innate and adaptive immune responses but also can contribute to many inflammatory and autoimmune diseases when dysregulated. This review focuses on the β ₂ integrins, the principal integrins expressed on leukocytes. We review their discovery and role in host defense, the structural basis for their ligand recognition and activation, and their potential as therapeutic targets.

The Brain Proteome of the Ubiquitin Ligase Peli1 Knock-Out Mouse during Experimental Autoimmune Encephalomyelitis

The ubiquitin ligase Peli1 has previously been suggested as a potential treatment target in multiple sclerosis. In the multiple sclerosis disease model, experimental autoimmune encephalomyelitis, Peli1 knock-out led to less activated microglia and less inflammation in the central nervous system. Despite being important in microglia, Peli1 expression has also been detected in glial and neuronal cells. In the present study the overall brain proteomes of Peli1 knock-out mice and wild-type mice were compared prior to experimental autoimmune encephalomyelitis induction, at onset of the disease and at disease peak. Brain samples from the frontal hemisphere, peripheral from the extensive inflammatory foci, were analyzed using TMT-labeling of sample pools, and the discovered proteins were verified in individual mice using label-free proteomics. The greatest proteomic differences between Peli1 knock-out and wild-type mice were observed at the disease peak. In Peli1 knock-out a higher degree of antigen presentation, increased activity of adaptive and innate immune cells and alterations to proteins involved in iron metabolism were observed during experimental autoimmune encephalomyelitis. These results unravel global effects to the brain proteome when abrogating Peli1 expression, underlining the importance of Peli1 as a regulator of the immune response also peripheral to inflammatory foci during experimental autoimmune encephalomyelitis.

The proteomics data is available in PRIDE with accession PXD003710.

Transcriptome signature for dampened Th2 dominance in acellular pertussis vaccine-induced CD4(+) T cell responses through TLR4 ligation

Current acellular pertussis (aP) vaccines promote a T helper 2 (Th2)-dominated response, while Th1/Th17 cells are protective. As our previous study showed, after adding a non-toxic TLR4 ligand, LpxL1, to the aP vaccine in mice, the Bordetella pertussis-specific Th2 response is decreased and Th1/Th17 responses are increased as measured at the cytokine protein level. However, how this shift in Th response by LpxL1 addition is regulated at the gene expression level remains unclear. Transcriptomics analysis was performed on purified CD4(+) T cells of control and vaccinated mice after in vitro restimulation with aP vaccine antigens. Multiple key factors in Th differentiation, including transcription factors, cytokines, and receptors, were identified within the differentially expressed genes. Upregulation of Th2- and downregulation of follicular helper T cell-associated genes were found in the CD4(+) T cells of both aP- and aP+LpxL1-vaccinated mice. Genes exclusively upregulated in CD4(+) T cells of aP+LpxL1-vaccinated mice included Th1 and Th17 signature cytokine genes Ifng and Il17a respectively. Overall, our study indicates that after addition of LpxL1 to the aP vaccine the Th2 component is not downregulated at the gene expression level. Rather an increase in expression of Th1- and Th17-associated genes caused the shift in Th subset outcome.

Update on macrophages and innate immunity in scleroderma

PURPOSE OF REVIEW

In this review of the literature from 2014 through mid-2015, we examine new data that shed light on how macrophages and other innate immune cells and signals contribute to inflammation, vascular dysfunction, and fibrosis in scleroderma.

RECENT FINDINGS

Recent human studies have focused on changes early in scleroderma, and linked macrophages to inflammation in skin and progression of lung disease. Plasmacytoid dendritic cells have been implicated in vascular dysfunction. In mice, several factors have been identified that influence macrophage activation and experimental fibrosis. However, emerging data also suggest that myeloid cells can have differential effects in fibrosis. Sustained signaling through different toll-like receptors can lead to inflammation or fibrosis, and these signals can influence both immune and nonimmune cells.

SUMMARY

There are many types of innate immune cells that can potentially contribute to scleroderma and will be worth exploring in detail. Experimentally dissecting the roles of macrophages based on ontogeny and activation state, and the innate signaling pathways in the tissue microenvironment, may also lead to better understanding of scleroderma pathogenesis.

The role of macrophage 1 antigen in polymicrobial sepsis

PURPOSE

Macrophage 1 antigen (Mac-1, CD11bCD18) is a leukocyte adhesion molecule that is involved in many functions including leukocyte recruitment, phagocytosis, and neutrophil apoptosis. The previous report of mild polymicrobial, abdominal sepsis showed that the administration of anti-CD11b-blocking antibody administration attenuated lung injury without any survival benefit. Here we tested the impact of Mac-1 deficiency in severe polymicrobial abdominal sepsis model.

METHODS

Polymicrobial sepsis was studied using cecal ligation and puncture model in wild-type (WT) or Mac-1-deficient (CD11b knockout [KO]) mice, and their outcomes were examined. Bacterial tissue load and the recruitment of neutrophils to the abdominal cavity were assessed. In vitro bacterial killing assay was performed. Serum cytokine levels were measured using multiarray. Apoptosis of spleen tissues was assessed using Western blot analysis and immunohistochemistry (cleaved caspase 3 and TUNEL staining). In addition, in vitro apoptosis assay was performed using primary splenocytes from both WT and KO mice. The recruitment of neutrophils to lung was assessed by measuring myeloperoxidase activity.

RESULTS

Macrophage 1 antigen deficiency significantly decreased survival (survival percentage WT 43.5% vs. KO 13.0%; P = 0.0038) with higher bacterial load in blood and more severe systemic inflammation. Knockout mice demonstrated higher apoptosis both in vivo and in vitro. The recruitment of neutrophils to lung was not different between WT and KO mice.

CONCLUSIONS

Macrophage 1 antigen deficiency was associated with poorer outcomes, more bacterial load, systemic inflammation, and splenic apoptosis. However, Mac-1 deficiency did not attenuate neutrophil recruitment to lung.

Rare variants at 16p11.2 are associated with common variable immunodeficiency

BACKGROUND

Common variable immunodeficiency (CVID) is characterized clinically by inadequate quantity and quality of serum immunoglobulins with increased susceptibility to infections, resulting in significant morbidity and mortality. Only a few genes have been uncovered, and the genetic background of CVID remains elusive to date for the majority of patients.

OBJECTIVE

We sought to seek novel associations of genes and genetic variants with CVID.

METHODS

We performed association analyses in a discovery cohort of 164 patients with CVID and 19,542 healthy control subjects genotyped on the Immuno BeadChip from Illumina platform; replication of findings was examined in an independent cohort of 135 patients with CVID and 2,066 healthy control subjects, followed by meta-analysis.

RESULTS

We identified 11 single nucleotide polymorphisms (SNPs) at the 16p11.2 locus associated with CVID at a genome-wide significant level in the discovery cohort. The most significant SNP, rs929867 (P = 6.21 × 10(-9)), is in the gene fused-in-sarcoma (FUS), with 4 other SNPs mapping to integrin CD11b (ITGAM). Results were confirmed in our replication cohort. Conditional association analysis suggests a single association signal at the 16p11.2 locus. A strong trend of association was also seen for 38 SNPs (P < 5 × 10(-5)) in the MHC region, supporting that this is a genuine CVID locus. Interestingly, we found that 80% of patients with the rare ITGAM variants have reduced switched memory B-cell counts.

CONCLUSION

We report a novel association of CVID with rare variants at the FUS/ITGAM (CD11b) locus on 16p11.2. The association signal is enriched for promoter/enhancer markers in the ITGAM gene. ITGAM encodes the integrin CD11b, a part of complement receptor 3, a novel candidate gene implicated here for the first time in the pathogenesis of CVID.

Surface profiles of live colorectal cancer cells and tumor infiltrating lymphocytes from surgical samples correspond to prognostic categories

Extensive surface profiles of colorectal cancer (CRC) cells and tumor infiltrating lymphocytes (TIL) have been obtained from 45 surgical resection samples. Live cells were captured on an antibody microarray and stained with fluorescently-labeled antibodies. Minimal panels of 11 CRC antigens (CD13, CD24, CD26, CD49d, CD138, CD166, CA-125, CA19-9, EGFR, Galectin-4 and HLA-DR) and 11 T-cell antigens (CD10, CD11b, CD11c, CD25, CD31, CD95, CD151, CD181, Galectin-4, CA19-9, TSP-1) provide signatures for relapse and survival. Hierarchical clustering of profiles from CRC cells and TIL identified groups of patients for survival, systemic relapse and death. The groups from CRC and TIL profiles for systemic relapse showed 79.2% concordance, enabling prediction of relapse after surgery. The results demonstrate communication between CRC cells and TIL.

The phenotype and activation status of T and NK cells in porcine colostrum suggest these are central/effector memory cells

In pigs, the epitheliochorial placenta does not allow transfer of maternally derived antibodies or immune cells to the fetus. Thus, piglets are dependent on intake of colostrum for acquisition of passive immunity during the neonatal period. As well as immunoglobulin G (IgG), cellular components of colostrum, mainly lymphocytes, can enter the systemic circulation and secondary lymphoid organs of the neonate. In order to understand the function and immunological role of these cells, a flow cytometric study was undertaken to characterise the cellular profile and phenotype of T cells and NK cells present in porcine colostrum. The results indicated that the greatest numbers of lymphocytes were found on the first day of lactation. The predominant cell types in colostrum were CD8(+) single positive T cells (53.6%), followed by CD4(+)CD8(+) double positive T cells (21.1%), CD2(+)CD8(+) γδ T cells (15.0%) and NK cells (13.5%). CD4(+) single positive T cells (4.4%) and other γδ T cell subpopulations (1.8% CD2(-)CD8(-) and 0.4% CD2(+)CD8(-)) were present in colostrum at low levels. Although the profile of the T cell subpopulations during the first 3 days of lactation remained constant, the absolute numbers of T and NK cells decreased significantly in the first few hours of lactation. Expression of CCR7, CD11b, CD25, CD45RA and MHC class II was used to assess the activation status of T and NK cells in colostrum. T cell subpopulations expressed markers consistent with an effector memory phenotype, indicating that these were antigen-experienced cells. The phenotype of colostral T and NK cells suggests a role in mucosal immunity and potentially in transfer of passive immunity from sow to piglet.

Analysis of the effect of the active compound of green tea (EGCG) on the proliferation of peripheral blood mononuclear cells

Background

Cancer immunotherapy requires proper manipulation of the immune system, lymphocytes in particular, in order to identify and destroy the cancer cells as non-self. In this study we investigated the effect of the flavonoid present in green tea, namely epigallocatechin-3-gallate (EGCG), on the proliferation of, and IFN-γ production by, peripheral blood mononuclear cells (PBMC) from breast cancer patients stimulated with a mitogen, anti-CD3 and the common breast cancer peptides Her-2/neu, and p53.

Methods

Blood samples were collected from 25 patients with breast cancer at the Kuwait Cancer Control Centre (KCCC). The patients were newly diagnosed, and had not undergone any treatment or surgery at the time of sample collection. The control group consisted of 25 healthy women age-matched (±5 years) to the patients. PBMC were isolated from the patients and controls, and were cultured separately with the mitogen PHA, anti-CD3 antibodies, and Her-2/neu and p53 in the presence or absence of standardized doses of EGCG. The degree of proliferation and interferon-γ [IFN-γ) release were then analyzed.

Results

EGCG significantly suppressed the proliferation of PBMC in response to stimulation separately with (i) the mitogen, (ii) anti-CD3, and (iii) the cancer antigen peptides. IFN-γ production was also significantly suppressed by EGCG in vitro.

Conclusions

EGCG appears to have an immunosuppressive effect on the proliferation of PBMC, indicating that EGCG is worth exploring for immunomodulatory effects in autoimmune diseases and tissue transplantation.

Early treatment with anti-VLA-4 mAb can prevent the infiltration and/or development of pathogenic CD11b+CD4+ T cells in the CNS during progressive EAE

Natalizumab is a humanized monoclonal antibody against the leukocyte adhesion molecule very late antigen (VLA)-4, and is currently an approved therapy for patients with relapsing-remitting multiple sclerosis (RRMS). However, it is unknown whether natalizumab is beneficial for progressive forms of MS. Therefore, we assessed the effects of anti-VLA-4 monoclonal antibody (mAb) therapy in a progressive experimental autoimmune encephalomyelitis (EAE) mouse model. Notably, we found that early therapy could significantly reduce the severity of progressive EAE, while treatment initiated at an advanced stage was less efficient. Furthermore, we observed the accumulation of a novel subset of GM-CSF-producing CD11b+CD4+ T cells in the CNS throughout disease progression. Importantly, early therapeutic anti-VLA-4 mAb treatment suppressed the accumulation of these GM-CSF-producing CD11b+CD4+ T cells in the CNS along with activated microglia/macrophages populations, and also conferred a protective effect against inflammation-mediated neurodegeneration, including demyelination and axonal loss. Collectively, our data suggest that early treatment with anti-VLA-4 mAb can provide neuroprotection against progressive CNS autoimmune disease by preventing the accumulation of pathogenic GM-CSF-producing CD11b+CD4+ T cells in the CNS.

Infectious versus non-infectious loosening of implants: activation of T lymphocytes differentiates between the two entities

PURPOSE

Loosening of implants occurs mainly for two reasons: bacterial infection of the implant or "aseptic loosening" presumably due to wear particles derived from the implant. To gain further insight into the pathomechanism, we analysed activation of the T cell response in these patients.

METHODS

Activation of peripheral T lymphocytes was determined by cytofluorometry as down-regulation of CD28 and up-regulation of CD11b. In addition, tissue samples obtained during surgery were analysed by quantitative RT-PCR for gene expression of CD3, CD14 and cathepsin K, as markers for T cells, monocytes/macrophages or osteoclasts, respectively.

RESULTS

Activated T lymphocytes were detected in patients with infection but not in patients with aseptic loosening. Gene expression of CD3 was significantly enhanced in tissues of patients with infection compared to those with aseptic loosening. Expression of CD14 and of cathepsin K did not differ between the two groups.

CONCLUSION

Implant-associated infection and aseptic loosening are associated with a local inflammatory response, which eventually results in osteoclastogenesis and bone resorption. Systemic T cell activation, in contrast, occurs only in patients with implant-associated infection, and hence analysis of T cell activation markers could serve as a diagnostic tool to differentiate between the two entities.

Differences in T-cell responses between Mycobacterium tuberculosis and Mycobacterium africanum-infected patients

In The Gambia, Mycobacterium tuberculosis (Mtb) and Mycobacterium africanum (Maf) are major causes of tuberculosis (TB). Maf is more likely to cause TB in immune suppressed individuals, implying differences in virulence. Despite this, few studies have assessed the underlying immunity to the two pathogens in human. In this study, we analyzed T-cell responses from 19 Maf- and 29 Mtb-infected HIV-negative patients before and after TB chemotherapy following overnight stimulation of whole blood with TB-specific antigens. Before treatment, percentages of early secreted antigenic target-6(ESAT-6)/culture filtrate protein-10(CFP-10) and purified protein derivative-specific single-TNF-α-producing CD4(+) and CD8(+) T cells were significantly higher while single-IL-2-producing T cells were significantly lower in Maf- compared with Mtb-infected patients. Purified protein derivative-specific polyfunctional CD4(+) T cells frequencies were significantly higher before than after treatment, but there was no difference between the groups at both time points. Furthermore, the proportion of CD3(+) CD11b(+) T cells was similar in both groups pretreatment, but was significantly lower with higher TNF-α, IL-2, and IFN-γ production in Mtb- compared with that of Maf-infected patients posttreatment. Our data provide evidence of differences in T-cell responses to two mycobacterial strains with differing virulence, providing some insight into TB pathogenesis with different Mtb strains that could be prospectively explored as biomarkers for TB protection or susceptibility.

Linking complement and anti-dsDNA antibodies in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus is a severe autoimmune disease that affects multiple organ systems resulting in diverse symptoms and outcomes. It is characterized by antibody production to a variety of self-antigens, but it is specifically associated with those against anti-dsDNA. Anti-dsDNA antibodies are present before the onset of clinical disease and are associated with severe manifestations of lupus such as glomerulonephritis. Their levels fluctuate with changes in disease activity and, in combination with the levels of complement proteins C3 and C4, are strong indicators of disease flare and treatment response in patients with lupus. The decreased complement levels that are noted during flares of lupus activity are believed to be secondary to increased autoantibody production and immune complex formation that results in tissue damage; however, recent data suggest that complement activation can also drive development of these pathogenic autoantibodies. This review will explore the various roles of complement in the development and pathogenesis of anti-dsDNA antibodies.

Mac1+/Gr1+ cells contribute to transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a serious complication associated with blood transfusion and can cause transfusion associated fatalities. Both antibody dependent and non-dependent mechanisms are involved in TRALI, as proposed over the past years. Nonetheless, many details of the immune cells involved in TRALI, particularly the Mac1(+)/Gr1(+) cells from donors, are not fully understood yet. Here we used an in vitro transwell system and a mouse model to study the role of donor leukocytes, present in the donor material, in the occurrence of TRALI reactions. We found that there is a number of immature myeloid cells with Mac1(+)/Gr1(+) phenotype present in the red blood cell (RBC) products, when prepared by regular methods. We found that murine Mac1(+)/Gr1(+) cells from stored RBC products display an elevated MHC I and CD40 expression, as well as an enhanced tumor necrosis factor alpha(TNF-α), interlukin-6(IL-6) and macrophage inflammatory protein 2 (MIP-2) secretion. When tested in a transwell endothelial migration assay, Mac1(+)/Gr1(+) cells showed a significant capability to cross the endothelial barrier. In vivo investigation demonstrated that compared to the purified RBC transfusion, more murine Mac1(+)/Gr1(+) cells from the regular method produced RBC sequestered in the lung, which associated to shorter survival. Taken together, these data suggest that donor derived Mac1(+)/Gr1(+) cells can play a significant role in TRALI reactions, and that reduction of Mac1(+)/Gr1(+) cell number from RBC products is necessary to control the severity of TRALI reactions in clinic.

Role of LFA-1 in the activation and trafficking of T cells: implications in the induction of chronic colitis

INTRODUCTION

We have previously demonstrated that adoptive transfer of naïve CD4(+) T cells devoid of lymphocyte function-associated antigen-1-deficient (LFA-1; CD11a/CD18) into recombination activating gene-1 (RAG-1) deficient (RAG(-/-) ) mice fails to induce chronic colitis whereas transfer of wild type (WT) T-cells induces unrelenting and chronic disease.

METHODS

The objectives of this study were to assess the role of lymphocyte function-associated antigen-1 (LFA-1) in enteric antigen (EAg)-induced activation of T cells in vitro and in vivo and to define the importance of this integrin in promoting trafficking of T cells to the mesenteric lymph nodes (MLNs) and colon.

RESULTS

We found that EAg-pulsed dendritic cells (DCs) induced proliferation of LFA-1-deficient (CD11a(-/-) ) CD4(+) T cells that was very similar to that induced using WT T cells, suggesting that LFA-1 is not required for activation/proliferation of T cells in vitro. Coculture of WT or CD11a(-/-) T cells with EAg-pulsed DCs induced the generation of similar amounts of interferon-gamma, interleukin (IL)-4, and IL-10, whereas IL-17A production was reduced ≈ 2-fold in cocultures with CD11a(-/-) T cells. Short-term (20-22 hours) trafficking studies demonstrated that while both WT and CD11a(-/-) T cells migrated equally well into the spleen, liver, lungs, small intestine, cecum, and colon, trafficking of CD11a(-/-) T cells to the MLNs was reduced by 50% when compared to WT T cells. When the observation period was extended to 3-7 days posttransfer, we observed ≈ 2-3-fold more WT T cells within the MLNs and colon than CD11a(-/-) T cells, whereas T-cell proliferation (as measured by CFSE dilution) was comparable in both populations.

CONCLUSIONS

Taken together, our data suggest that LFA-1 is not required for EAg-induced activation of CD4(+) T cells in vitro or in vivo but is required for trafficking of T cells to the MLNs and homing of colitogenic effector cells to the colon where they initiate chronic gut inflammation.

α(M)β(2)-integrin-intercellular adhesion molecule-1 interactions drive the flow-dependent trafficking of Guillain-Barré syndrome patient derived mononuclear leukocytes at the blood-nerve barrier in vitro

The mechanisms of hematogenous leukocyte trafficking at the human blood-nerve barrier (BNB) are largely unknown. Intercellular adhesion molecule-1 (ICAM-1) has been implicated in the pathogenesis of Guillain-Barré syndrome (GBS). We developed a cytokine-activated human in vitro BNB model using primary endoneurial endothelial cells. Endothelial treatment with 10 U/ml tissue necrosis factor-α and 20 U/ml interferon-γ resulted in de novo expression of pro-inflammatory chemokines CCL2, CXCL9, CXCL11, and CCL20, with increased expression of CXCL2-3, CXCL8, and CXCL10 relative to basal levels. Cytokine treatment induced/enhanced ICAM-1, E- and P-selectin, vascular cell adhesion molecule-1 and the alternatively spliced pro-adhesive fibronectin variant, fibronectin connecting segment-1 expression in a time-dependent manner, without alterations in junctional adhesion molecule-A expression. Lymphocytes and monocytes from untreated GBS patients express ICAM-1 counterligands, α(M)- and α(L)-integrin, with differential regulation of α(M) -integrin expression compared to healthy controls. Under flow conditions that mimic capillary hemodynamics in vivo, there was a >3-fold increase in total GBS patient and healthy control mononuclear leukocyte adhesion/migration at the BNB following cytokine treatment relative to the untreated state. Function neutralizing monoclonal antibodies against human α(M)-integrin (CD11b) and ICAM-1 reduced untreated GBS patient mononuclear leukocyte trafficking at the BNB by 59% and 64.2%, respectively. Monoclonal antibodies against α(L)-integrin (CD11a) and human intravenous immunoglobulin reduced total leukocyte adhesion/migration by 22.8% and 17.6%, respectively. This study demonstrates differential regulation of α(M)-integrin on circulating mononuclear cells in GBS, as well as an important role for α(M)-integrin-ICAM-1 interactions in pathogenic GBS patient leukocyte trafficking at the human BNB in vitro.

CR3 is the dominant phagocytotic complement receptor on human dendritic cells

Dendritic cells (DCs) play a decisive role in immunity; they interact with various pathogens via several pattern recognition and different opsonophagocytotic receptors, including Fc- and complement-receptors. β2-integrins, including complement receptors CR3 (CD11b/CD18) and CR4 (CD11c/CD18) participate in many immunological processes, especially those involving cell migration, adherence, and phagocytosis. Human monocyte derived dendritic cells (MDCs) are known to express CR3 as well as CR4, however possible differences regarding the role of these receptors has not been addressed so far. Our aim was to explore whether there is a difference between the binding and uptake of various complement-opsonized microorganisms, mediated by CR3 and CR4. Studying the expression of receptors during differentiation of MDCs we found that the appearance of CD11b decreased, whereas that of CD11c increased. Interestingly, both receptors were present in the cell membrane in an active conformation. Here we demonstrate that ligation of CD11b directs MDCs to enhanced phagocytosis, while the maturation of the cells and their inflammatory cytokine production are not affected. Blocking CD11c alone did not change the uptake of opsonized yeast or bacteria by MDCs. We confirmed these results using siRNA; namely downregulation of CD11b blocked the phagocytosis of microbes while silencing CD11c had no effect on their uptake. Our data clearly demonstrate that complement C3-dependent phagocytosis of MDCs is mediated mainly by CR3.

Regulation of inflammatory chemokine receptors on blood T cells associated to the circulating versus liver chemokines in dengue fever

Little is known about the role of chemokines/chemokines receptors on T cells in natural DENV infection. Patients from DENV-2 and -3- outbreaks were studied prospectively during the acute or convalescent phases. Expression of chemokine receptor and activation markers on lymphocyte subpopulations were determined by flow cytometry analysis, plasma chemokine ligands concentrations were measured by ELISA and quantification of CCL5/RANTES⁺ cells in liver tissues from fatal dengue cases was performed by immunochemistry. In the acute DENV-infection, T-helper/T-cytotoxic type-1 cell (Th1/Tc1)-related CCR5 is significantly higher expressed on both CD4 and CD8 T cells. The Th1-related CXCR3 is up-regulated among CD4 T cells and Tc2-related CCR4 is up-regulated among CD8 T cells. In the convalescent phase, all chemokine receptor or chemokine ligand expression tends to reestablish control healthy levels. Increased CCL2/MCP-1 and CCL4/MIP-1β but decreased CCL5/RANTES levels were observed in DENV-patients during acute infection. Moreover, we showed an increased CD107a expression on CCR5 or CXCR3-expressing T cells and higher expression of CD29, CD44^HIGH and CD127^LOW markers on CCR4-expressing CD8 T cells in DENV-patients when compared to controls. Finally, liver from dengue fatal patients showed increased number of cells expressing CCL5/RANTES in three out of four cases compared to three death from a non-dengue patient. In conclusion, both Th1-related CCR5 and CXCR3 among CD4 T cells have a potential ability to exert cytotoxicity function. Moreover, Tc1-related CCR5 and Tc2-related CCR4 among CD8 T cells have a potential ability to exert effector function and migration based on cell markers evaluated. The CCR5 expression would be promoting an enhanced T cell recruitment into liver, a hypothesis that is corroborated by the CCL5/RANTES increase detected in hepatic tissue from dengue fatal cases. The balance between protective and pathogenic immune response mediated by chemokines during dengue fever will be discussed.

Effects of long-term moderate ethanol and cholesterol on cognition, cholinergic neurons, inflammation, and vascular impairment in rats

There is strong evidence that vascular risk factors play a role in the development of Alzheimer's disease (AD) or vascular dementia (vaD). Ethanol (EtOH) and cholesterol are such vascular risk factors, and we recently showed that hypercholesterolemia causes pathologies similar to AD [Ullrich et al. (2010) Mol Cell Neurosci 45, 408–417]. The aim of this study was to investigate the effects of long-term (12 months) EtOH treatment (20% v/v in drinking water) alone or long-term 5% cholesterol diet alone or a combination (mix) in adult Sprague–Dawley rats. Long-term EtOH treatment (plasma EtOH levels 58±23 mg/dl) caused significant impairment of spatial memory, reduced the number of choline acetyltransferase- and p75 neurotrophin receptor-positive nucleus basalis of Meynert neurons, decreased cortical acetylcholine, elevated cortical monocyte chemoattractant protein-1 and tissue-type plasminogen activator, enhanced microglia, and markedly induced anti-rat immunoglobulin G-positive blood–brain barrier leakage. The effect of long-term hypercholesterolemia was similar. Combined long-term treatment of rats with 20% EtOH and 5% cholesterol (mix) did not potentiate treatment with EtOH alone, but instead counteracted some of the EtOH-associated effects. In conclusion, our data show that vascular risk factors EtOH and cholesterol play a role in cognitive impairment and possibly vaD.