Basophils, IgE, and autoantibody-mediated kidney disease

Stratification of Kidney Transplant Recipients Into Five Subgroups Based on Temporal Disease Trajectories

Background

Kidney transplantation is the treatment of choice for patients with end-stage renal disease. Considerable clinical research has focused on improving graft survival and an increasing number of kidney recipients die with a functioning graft. There is a need to improve patient survival and to better understand the individualized risk of comorbidities and complications. Here, we developed a method to stratify recipients into similar subgroups based on previous comorbidities and subsequently identify complications and for a subpopulation, laboratory test values associated with survival.

Methods

First, we identified significant disease patterns based on all hospital diagnoses from the Danish National Patient Registry for 5752 kidney transplant recipients from 1977 to 2018. Using hierarchical clustering, these longitudinal patterns of diseases segregate into 3 main clusters of glomerulonephritis, hypertension, and diabetes. As some recipients are diagnosed with diseases from >1 cluster, recipients are further stratified into 5 more fine-grained trajectory subgroups for which survival, stratified complication patterns as well as laboratory test values are analyzed.

Results

The study replicated known associations indicating that diabetes and low levels of albumin are associated with worse survival when investigating all recipients. However, stratification of recipients by trajectory subgroup showed additional associations. For recipients with glomerulonephritis, higher levels of basophils are significantly associated with poor survival, and these patients are more often diagnosed with bacterial infections. Additional associations were also found.

Conclusions

This study demonstrates that disease trajectories can confirm known comorbidities and furthermore stratify kidney transplant recipients into clinical subgroups in which we can characterize stratified risk factors. We hope to motivate future studies to stratify recipients into more fine-grained, homogenous subgroups to better discover associations relevant for the individual patient and thereby enable more personalized disease-management and improve long-term outcomes and survival.

Serum IgE anti-dsDNA autoantibodies in patients with proliferative lupus nephritis are associated with tubulointerstitial inflammation

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the overproduction of multiple autoantibodies. Lupus nephritis (LN), the most common cause of morbidity and mortality, requires early detection. However, only a limited number of serum biomarkers have been associated with the disease activity of LN. Serum IgE anti-dsDNA autoantibodies are prevalent in patients with SLE and may be associated with the pathogenesis of LN. In this study, serum samples from 88 patients with biopsy-proven proliferative LN were collected along with complete clinical and pathological data to investigate the clinical and pathological associations of anti-dsDNA IgE autoantibodies using ELISA. This study found that the prevalence of IgE anti-dsDNA autoantibodies in patients with proliferative LN was 38.6% (34/88). Patients with anti-dsDNA IgE autoantibodies were more prone to acute kidney injury (17/34 vs. 14/54; p = .025). Levels of anti-dsDNA IgE autoantibodies were associated with interstitial inflammation (r = 0.962, p = .017). Therefore, anti-dsDNA IgE autoantibody levels are associated with tubulointerstitial inflammation in patients with proliferative LN.

Aerofloral studies and allergenicity of dominant pollen types in Taraba and Bauchi States of Northeastern Nigeria

Pollen and spores have been identified as major airborne bio-particles inducing respiratory disorders including allergic rhinitis and atopic dermatitis among hypersensitive individuals. The present study was conducted with a view to investigating monthly depositional rate of atmospheric palynomorphs to determine the influence of the immediate vegetation on airborne pollen distribution; allergenic activities of dominant atmospheric pollen types at selected study locations in Taraba and Bauchi States, Northeastern Nigeria. Bioaerosols were collected using Tauber-like pollen traps and subjected to standard palynological treatment procedures, microscopy and photomicrography. Plant enumeration within the surrounding vegetation revealed that some airborne pollen types were produced by local plants at the study locations. Spores of Nephrolepis sp., Pteris sp. and a trilete fern, as well as diatoms were also recovered. Crude protein contents of some dominant pollen types; Borreria verticillata (L.) G.F.W. Meyer and Panicum maximum Jacq. for Taraba State; Leucaena leucocephala (Lam.) de Wit. and Terminalia catappa L. for Bauchi State, were quantified and extracted to sensitize Mus musculus mice for serology (ELISA) and haematology (differential and total white blood cell counts). Statistical significance was tested and recorded in the correlation between levels of serological and haematological parameters elicited by each test group; differences between levels of these parameters elicited by each test group and those of the control, as well as at varying sensitization periods. In the Leucaena leucocephala test group, swollen body and histopathological morbid features showing more extensive areas of inflammatory cells and alveoli filled with fluid in the lungs, were recorded in two dead M. musculus, respectively. The study revealed that all the tested pollen types are possible allergens at the study locations, establishing a complexity of interaction among allergy mediators at varied periods of mice sensitization and forming a paradigm of human immune response to the different pollen allergens.

Single-cell analysis identifies the interaction of altered renal tubules with basophils orchestrating kidney fibrosis

Inflammation is an important component of fibrosis but immune processes that orchestrate kidney fibrosis are not well understood. Here we apply single-cell sequencing to a mouse model of kidney fibrosis. We identify a subset of kidney tubule cells with a profibrotic-inflammatory phenotype characterized by the expression of cytokines and chemokines associated with immune cell recruitment. Receptor-ligand interaction analysis and experimental validation indicate that CXCL1 secreted by profibrotic tubules recruits CXCR2+ basophils. In mice, these basophils are an important source of interleukin-6 and recruitment of the TH17 subset of helper T cells. Genetic deletion or antibody-based depletion of basophils results in reduced renal fibrosis. Human kidney single-cell, bulk gene expression and immunostaining validate a function for basophils in patients with kidney fibrosis. Collectively, these studies identify basophils as contributors to the development of renal fibrosis and suggest that targeting these cells might be a useful clinical strategy to manage chronic kidney disease.

The roles of basophils in mediating the immune responses

Basophils are the rarest blood cell population and have not been extensively studied. Our understanding of the functions of basophils is limited to their roles as the main effector cells in hypersensitivity reactions. Similar to mast cells, basophils express high-affinity IgE receptor (FcεRI), contain granules, and release hypersensitivity-associated mediators (such as histamine). The roles of basophils have not been fully elucidated; however, with the rapid development of monoclonal techniques, high-purity cell sorting techniques, and basophil-deficient mouse models, understanding of the functions and phenotypes of basophils has increased. This facilitates further investigations on the relationships between basophils and host immunity. Basophils are not only involved in mediating the generation of allergic reactions but also play important roles in immunomodulation and are responsible for the onset of infectious, allergic, and autoimmune diseases. In this review, we summarize the progress in understanding the roles of basophils in mediating immune responses with an emphasis on autoimmune diseases, particularly systemic lupus erythematosus and rheumatoid arthritis.

Innate Immune Cells and Hypertension: Neutrophils and Neutrophil Extracellular Traps (NETs)

Uncontrolled immune system activation amplifies end-organ injury in hypertension. Nonetheless, the exact mechanisms initiating this exacerbated inflammatory response, thereby contributing to further increases in blood pressure (BP), are still being revealed. While participation of lymphoid-derived immune cells has been well described in the hypertension literature, the mechanisms by which myeloid-derived innate immune cells contribute to T cell activation, and subsequent BP elevation, remains an active area of investigation. In this article, we critically analyze the literature to understand how monocytes, macrophages, dendritic cells, and polymorphonuclear leukocytes, including mast cells, eosinophils, basophils, and neutrophils, contribute to hypertension and hypertension-associated end-organ injury. The most abundant leukocytes, neutrophils, are indisputably increased in hypertension. However, it is unknown how (and why) they switch from critical first responders of the innate immune system, and homeostatic regulators of BP, to tissue-damaging, pro-hypertensive mediators. We propose that myeloperoxidase-derived pro-oxidants, neutrophil elastase, neutrophil extracellular traps (NETs), and interactions with other innate and adaptive immune cells are novel mechanisms that could contribute to the inflammatory cascade in hypertension. We further posit that the gut microbiota serves as a set point for neutropoiesis and their function. Finally, given that hypertension appears to be a key risk factor for morbidity and mortality in COVID-19 patients, we put forth evidence that neutrophils and NETs cause cardiovascular injury post-coronavirus infection, and thus may be proposed as an intriguing therapeutic target for high-risk individuals. © 2021 American Physiological Society. Compr Physiol 11:1575-1589, 2021.

IgE-Mediated Immune Response and Antibody-Mediated Rejection

BACKGROUND AND OBJECTIVES

Active antibody-mediated rejection is the main cause of kidney transplant loss, sharing with SLE the alloimmune response and the systemic activation of the IFN-α pathway. IgE-mediated immune response plays a key role in the development of SLE nephritis and is associated with IFN-α secretion. The aim of our study was to investigate IgE-mediated immune response in antibody-mediated rejection.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a cross-sectional study of 56 biopsy-proven antibody-mediated rejection study participants, 80 recipients with normal graft function/histology (control), 16 study participants with interstitial fibrosis/tubular atrophy, and six participants with SLE. We evaluated graft IgE deposition, tryptase (a mast cell marker), and CD203 (a specific marker of activated basophils) by immunofluorescence/confocal microscopy. In addition, we measured serum concentration of human myxovirus resistance protein 1, an IFN-α-induced protein, and anti-HLA IgE.

RESULTS

We observed a significantly higher IgE deposition in tubules and glomeruli in antibody-mediated rejection (1766±79 pixels) and SLE (1495±43 pixels) compared with interstitial fibrosis/tubular atrophy (582±122 pixels) and control (253±50 pixels). Patients with antibody-mediated rejection, but not control patients and patients with interstitial fibrosis/tubular atrophy, presented circulating anti-HLA IgE antibodies, although with a low mean fluorescence intensity. In addition, immunofluorescence revealed the presence of both mast cells and activated basophils in antibody-mediated rejection but not in control and interstitial fibrosis/tubular atrophy. The concentration of circulating basophils was significantly higher in antibody-mediated rejection compared with control and interstitial fibrosis/tubular atrophy. MxA serum levels were significantly higher in antibody-mediated rejection compared with control and correlated with the extent of IgE deposition.

CONCLUSIONS

Our data suggest that IgE deposition and the subsequent recruitment of basophils and mast cells within the kidney transplant might play a role in antibody-mediated rejection.

Elevated interleukin-25 and its association to Th2 cytokines in systemic lupus erythematosus with lupus nephritis

Systemic lupus erythematosus (SLE) is an autoimmune disorder that is associated with lupus nephritis, initiated by the deposition of immune complexes in the kidney; subsequently, this induces the overexpression of cytokines. Lupus nephritis is known as one of the major clinical manifestations that affect the disease severity in SLE patients. An increased number of resident periglomerular and immune cells in the kidney has the potential to affect the equilibrium of different immune cell subsets, such as Th1, Th2, Th17, and Tregs, which may be central to the induction of tissue damage in kidney by exerting either proinflammatory or anti-inflammatory effects, or both. This equilibrium has yet to be confirmed, as new players such as IL-25 remain undiscovered. IL-25 is a cytokine of the IL-17 family, which stimulates Th2-mediated immune response when overly expressed. Thus, the aim of this research is to determine the plasma levels of IL-25 and Th2-associated cytokines (IL-4, IL-5, IL-6, IL-9, IL-10, IL-13) in SLE patients with (SLE-LN) and without lupus nephritis. Sixty-four (n = 64) SLE patients and fifteen (n = 15) healthy individuals were recruited. This study demonstrated that the IL-9, IL-10 and IL-25 had significantly increased expressions in SLE-LN, followed by SLE without LN, compared to healthy controls. Meanwhile, IL-5 and IL-6 had significantly reduced. No significant difference was observed with IL-13, while the level of IL-4 was undetectable. Furthermore, IL-9 and IL-10 were significantly correlated with the IL-25, and IL-25, IL-9 and IL-10 were positively correlated with the disease severity score, SLEDAI. In conclusion, IL-25 and its associated Th2 cytokines (IL-9 and IL-10) may be involved in SLE pathogenesis. These cytokines could be potential biomarkers in monitoring and predicting the disease severity during SLE pathogenesis.

Rethinking the role of immunoglobulin E and its high-affinity receptor: new insights into allergy and beyond

Immunoglobulin E (IgE) and its high-affinity receptor (FcεRI) are well-known participants in the allergic response. The interaction of allergens with FcεRI-bound IgE antibodies is an essential step in mast cell/basophil activation and the subsequent release of allergic mediators. It is known that the affinity of the interaction between an IgE antibody and an allergen may differ, raising the question of whether FcεRI can decipher these differences. If so, do the cellular and physiological outcomes vary? Are the molecular mechanisms initiated by FcεRI similarly under low- or high-affinity interactions? Could the resulting inflammatory response differ? Recent discoveries summarized herein are beginning to shed new light on these important questions. What we have learned from them is that IgE and FcεRI form a complex regulatory network influencing the inflammatory response in allergy and beyond.

Activation of basophils is a new and sensitive marker of biocompatibility in hemodialysis

The hemodialysis procedure involves contact between peripheral blood and the surface of dialyzer membranes, which may lead to alterations in the pathways of innate and adaptive immunity. We aimed to study the effect of blood–membrane interaction on human peripheral basophils and neutrophils in hemodialysis with high- and low-permeability polysulfone dialyzers. The surface expression of CD203c (basophil selection marker) and CD63 (activation marker) after activation by the bacterial peptide formyl-methionyl-leucyl-phenylalanine (fMLP) or anti-Fcε receptor I (FcεRI) antibody and the absolute number of basophils was investigated before and after hemodialysis with each of the dialyzers. Moreover, the expression on neutrophils of CD11b, the CD11b active epitope, and CD88 was analyzed in the same groups of individuals. The expression of CD63 in basophils following activation by fMLP was significantly higher in the patient group compared with that in healthy controls, but no differences were observed after activation by anti-FcεRI. During the hemodialysis procedure, the low-flux membrane induced up-regulation of CD63 expression on basophils, while passage through the high-flux membrane did not significantly alter the responsiveness. In addition, the absolute number of basophils was unchanged after hemodialysis with either of the dialyzers and compared with healthy controls. We found no significant differences in the expression of the neutrophil activation markers (CD11b, the active epitope of CD11b, and CD88) comparing the two different dialyzers before and after dialysis and healthy controls. Together, these findings suggest that alterations in basophil activity may be a useful marker of membrane bioincompatibility in hemodialysis.

Autoreactive IgE is prevalent in systemic lupus erythematosus and is associated with increased disease activity and nephritis

The presence of autoantibodies in systemic lupus erythematosus, particularly those of the IgG subclass, have long been associated with disease onset and activity. Here we explored the prevalence of autoreactive IgE in SLE and its relevance to disease in French (n = 79) and United States (US) (n = 117) cohorts with a mean age of 41.5 ± 12.7 and 43.6 ± 15.3 years and disease duration of 13.5 ± 8.5 and 16.6 ± 11.9 years, respectively. Our findings show that approximately 65% of all SLE subjects studied produced IgE antibodies to the seven autoantigens tested. This positivity was increased to almost 83% when only those subjects with active disease were considered. SLE subjects who were positive for anti-dsDNA, -Sm, and -SSB/La -specific IgE showed a highly significant association in the levels of these antibodies with disease activity similar to that of the corresponding IgG's. A strong association of IgE autoantibodies with active nephritis was also found in the combined cohort analysis. A test of the predictive value of autoreactive IgE's and IgGs for disease activity (SLE Disease Activity Index (SLEDAI) ≥ 4) revealed that the best predictors were dsDNA-specific IgE and IgG, and that the age of an SLE subject influenced this predictive model. The finding argue that the overall levels of IgE autoantibodies, independently or in combination with IgG autoantibodies, may serve as indicators of active disease.

Circulating human basophils lack the features of professional antigen presenting cells

Recent reports in mice demonstrate that basophils function as antigen presenting cells (APC). They express MHC class II and co-stimulatory molecules CD80 and CD86, capture and present soluble antigens or IgE-antigen complexes and polarize Th2 responses. Therefore, we explored whether human circulating basophils possess the features of professional APC. We found that unlike dendritic cells (DC) and monocytes, steady-state circulating human basophils did not express HLA-DR and co-stimulatory molecules CD80 and CD86. Basophils remained negative for these molecules following stimulation with soluble Asp f 1, one of the allergens of Aspergillus fumigatus; Bet v 1, the major birch allergen; TLR2-ligand or even upon IgE cross-linking. Unlike DC, Asp f 1-pulsed basophils did not promote Th2 responses as analyzed by the secretion of IL-4 in the basophil-CD4⁺ T cell co-culture. Together, these results demonstrate the inability of circulating human basophils to function as professional APC.

Basophil modulation by cytokine instruction

Basophils have recently been recognized as critical effector cells in allergic reactions and protective immunity against helminths. Precise characterization of basophil biology could help to develop specific therapies that interfere with differentiation, tissue recruitment, or induction of effector functions and thereby ameliorate allergic disorders. The development, homeostasis, and effector functions of basophils are tightly regulated by extrinsic signals and in particular by cytokines. IL-3, GM-CSF, and thymic stromal lymphopoietin activate the STAT5 pathway that promotes proliferation, activation, and cytokine secretion but also induces a negative feedback loop via Pim-1 and SOCS proteins. Basophils further express receptors for IL-18 and IL-33, which are associated with the signaling adaptor MyD88 and activate the NF-κB and MAP kinase pathways. This review focuses on positive and negative regulation of basophils by these cytokines.

Recent developments in basophil research: do basophils initiate and perpetuate type 2 T-helper cell responses?

Basophils account for only 0.1-1% of all peripheral blood leukocytes. They were considered to be a redundant cell type for a long time. However, several findings show a non-redundant role for basophils in type 2 T-helper cell (Th2) immune responses in helminth infections, allergy and autoimmunity. Both immunoglobulin-E-dependent and -independent pathways have been described to contribute to basophil activation. In addition, several recent studies reported that basophils can function as antigen-presenting cells and are important in the initiation of Th2 immune responses. However, there are also conflicting studies that do not corroborate the importance of basophils in Th2 immune responses. This review discusses the role of basophils in Th2 immune responses in view of these recent findings.