Raised immunoglobulin A and circulating T follicular helper cells are linked to the development of food allergy in paediatric liver transplant patients

De Novo Food Allergy in Pediatric Recipients of Liver Transplant

ABSTRACT

Allergic and atopic conditions, including food allergy, asthma, eczema and eosinophilic disease of the gastrointestinal tract after liver transplant in previously non-allergic children have been increasingly described. After a liver transplant, children can present mild to severe reactions to food allergens (ie, from urticaria-angioedema to life-threatening anaphylactic reactions). De novo post-transplant food allergy may become clinically evident in children who undergo liver transplant between a few months and a few years of transplant. The present narrative review aims to describe the spectrum of de novo post-transplant food allergy development, the current theories of pathogenesis, risk factors and to suggest possible clinical management strategies.

Diversity of T Helper and Regulatory T Cells and Their Contribution to the Pathogenesis of Allergic Diseases

T helper (Th) and regulatory T (Treg) cells represent important effectors of adaptive immunity. They mediate communication between the immune system and tissue sites and thereby coordinate effective defense against environmental threats or maintain tolerance, respectively. Since the discovery of two prototypic T helper cells, Th1 and Th2, additional phenotypic and functional distinct subsets have been described ranging from Th17, Th22, Th9, and T follicular helper cells. The same holds true for regulatory T cells that represent a family with functionally distinct subsets characterized by co-expression of the transcription factors T-bet, Gata3, or RORγt. Here, we summarize the current knowledge on differentiation and function of T helper and regulatory T cell subsets and discuss their lineage stability versus plasticity towards other subsets. In addition, we highlight the direct and indirect contribution of each subset to the pathology of allergies and indicate novel therapies for specific targeting the effector functions of T helper and regulatory T cells.

Autoantibodies and Donor-specific Antibodies are Associated With Graft Dysfunction in Pediatric Liver Transplantation

OBJECTIVES

Autoantibodies (AAb) and donor-specific HLA antibodies (DSA) are frequently present in pediatric liver transplant (LT) recipients. Their clinical significance remains incompletely understood. We aimed to investigate the prevalence of serum AAb and DSA in pediatric LT recipients and its correlation with patient characteristics and histological and biochemical parameters.

METHODS

We retrospectively reviewed the data from 62 pediatric LT patients in follow-up at Ghent University Hospital between January 2007 and February 2018. Blood samples with AAb measurement were taken systematically, liver biopsies (LB) were performed on clinical indication.

RESULTS

AAb were detected in 27 (43.3%) patients, with antinuclear antibodies (ANA) being the most frequently (24%) encountered AAb. There was an association between AAb positivity and female gender (P = 0,032) and deceased donor LT (P = 0,006). Patients with positive AAb underwent a higher number of LB during their follow-up (P < 0,001), and an association was found with the presence of nonspecific histologic alterations (P = 0,032) in the absence of de novo autoimmune hepatitis. Positive AAb were also associated with higher alkaline phosphatase (P < 0,001), ALT (P < 0,001), AST (P < 0,001), γ-GT (P = 0,001), IgG (P = 0,011) and lower albumin (P = 0,029). Fourteen out of 50 (28%) patients were DSA-positive, mostly anti-HLA class II. DSA positivity was associated with T-cell-mediated rejection (P = 0,019), higher total (P = 0,033), and direct (P = 0,012) bilirubin and γ-GT (P < 0,001).

CONCLUSIONS

The presence of AAb and DSA is associated with histological and biochemical parameters of graft dysfunction. Larger prospective studies are warranted to investigate the causal relationships between AAb and DSA development and outcome parameters post pediatric LT.

Profiling circulating T follicular helper cells and their effects on B cells in post-cardiac transplant recipients

Background

To evaluate circulating T follicular helper (cTfh) cells and characterize their function in chronic-phase recipients after heart transplantation.

Methods

Participants were divided into healthy control (HC, n=40), preoperative (Pre, n=40), and post-transplantation chronic-phase recipient (1-year, n=40) groups. The percentages of cTfh cell subsets and CD19⁺ B cell subsets were measured using flow cytometry. In vitro co-culture experiments were performed using cTfh cells and B cells isolated by fluorescence-activated cell sorting. Plasma concentrations of IL-21, chemokine ligand 13 (CXCL13), immunoglobulin G1 (IgG1), and immunoglobulin G3 (IgG3) were quantified using enzyme-linked immunosorbent assays (ELISA).

Results

cTfh and programmed cell death protein 1-positive (PD-1⁺) cTfh cells, the cTfh17/cTfh ratio, and class-switched memory B cells in peripheral blood were significantly increased in the 1-year group versus the HC and Pre groups (P<0.01), whereas the cTfh1/cTfh ratio and number of naïve B cells were significantly decreased in the 1-year group. Co-culture experiments showed that cTfh cells promoted B cell differentiation to plasmablasts. In the 1-year group, cTfh and PD-1⁺ cTfh cell numbers were positively correlated with plasmablasts in CD19⁺ B cells (P<0.01). The cTfh17/cTfh ratio was positively correlated with IgG3 concentrations in plasma (P<0.01). The plasma concentrations of interleukin-21 (IL-21) and CXCL13 in the 1-year group were increased compared to the HC and Pre groups (P<0.05). Chronic-phase recipients had increased proportions of CD4⁺CXCR5⁺ and CD4⁺CXCR5⁺PD-1⁺ cTfh cells, with a cTfh1-to-cTfh17 subtype conversion. An increased number of cTfh cells was positively correlated with B cell differentiation to plasmablasts, class-switched memory B cells, and greater IgG production.

Conclusions

During the chronic phase, the proportion of cTfh cells increased and enhanced B cell responses. The cTfh-related soluble factors CXCL13 and IL-21 may regulate the immunopathogenesis of chronic immune injury. Thus, cTfh cells may drive long-term immune rejection in chronic-phase recipients after heart transplantation.

High Frequency of Concomitant Food Allergy Development and Autoantibody Formation in Children Who Have Undergone Liver Transplantation

BACKGROUND

Allergy and other immune-mediated diseases are more frequently reported in children who have undergone liver transplantation. Furthermore, autoantibodies are also prevalent, suggesting a state of immune dysregulation in these patients. Whether or not these processes occur simultaneously in the same individual has not been studied previously.

METHODS

A cohort of 43 children who had undergone liver transplantation for nonautoimmune liver disease at median age of 1.3 years was investigated for allergy and autoimmune disease. Sensitization to food and inhalant allergens was assessed, and autoantibodies were measured.

RESULTS

The prevalence of food allergy was 26% and that of respiratory allergy was 23%, whereas 33% and 26% of the subjects were sensitized to food and inhalant allergens, respectively. Autoimmune disease (ie, autoimmune hepatitis) occurred in a single individual (2%), whereas autoantibodies were present in 44% of the children. Food allergy and autoantibodies occurred concomitantly in 19% of the children, which was almost twice the frequency expected by chance (11%, P = 0.04). Respiratory allergy and the presence of autoantibodies were unrelated (12% concurrence versus the expected 10%, P = 0.73). In the logistic regression analysis, autoantibody formation was associated with discontinued immunosuppression and food allergy, with odds ratios of 13 (P = 0.01) and 7.1 (P = 0.03), respectively.

CONCLUSIONS

In contrast to respiratory allergy, food allergy and autoantibody formation occurred together in the same children who underwent liver transplantation at a frequency higher than would be expected by chance. This may reflect an underlying immune dysregulation that impairs immune tolerance to both food allergens and autoantigens.

Cytokine profile in children with food allergy following liver transplantation

BACKGROUND

LTX in children is associated with increased risk of food allergy, and the mechanisms underlying this are unknown. We wanted to study whether plasma cytokine profile differed in liver transplanted children, with and without food allergy, and whether it differed from untransplanted children with CLD.

METHODS

Plasma cytokines, total and specific IgE in nine patients with food allergy were compared with 13 patients without food allergy following LTX, and also with seven untransplanted patients with CLD.

RESULTS

No difference was found in the cytokine profile between liver transplanted patients with and without food allergy. Transplanted patients with food allergy having received a prescription of epinephrine had a significantly higher total IgE (2033 [234-2831] vs 10 [5-41] IU/L, P = .002) and MIP-1b (52 [37-96] vs 36 [32-39], P = .035) compared with transplanted patients without food allergy. Two patients with severe food allergy responded favorably to conversion from tacrolimus-based immunosuppression to MMF and corticosteroids with reduction in clinical symptoms, total IgE, specific IgE, IL-1ra, IL-4, RANTES, PDGF, MIP-1a, and TNFα. The transplantation group had higher levels of IL-1b, IL-5, IL-7, IL-13, GCSF, IFNγ, and MIP-1a compared with the CLD group.

CONCLUSIONS

No overall difference was found in plasma cytokine profile between patients with and without food allergy. Patients with severe food allergy had significant elevation of MIP-1b. Discontinuation of tacrolimus reduced total and specific IgE and changed plasma cytokine profile. The plasma cytokine profile in liver transplanted children was different compared with children with CLD.

Follicular regulatory T cells: a novel target for immunotherapy?

High‐affinity antibodies are produced during multiple processes in germinal centres (GCs), where follicular helper T (Tfh) cells interact closely with B cells to support B‐cell survival, differentiation and proliferation. Recent studies have revealed that a specialised subset of regulatory T cells, follicular regulatory T (Tfr) cells, especially fine‐tune Tfh cells and GC B cells, ultimately regulating GC reactions. Alterations in frequencies or function of Tfr cells may result in multiple autoantibody‐mediated or autoantibody‐associated diseases. This review discusses recent insights into the physiology and pathology of Tfr cells, with a special emphasis on their potential roles in human diseases. Discrepancies are common among studies, reflecting the limited understanding of Tfr cells. Further exploration of the mechanisms of Tfr cells in these diseases and thus targeting Tfr cells may help reinstate immune homeostasis and provide novel immunotherapy.

Food allergy phenotypes: The key to personalized therapy

Food allergies (FAs) are of increasing public health concern and are characterized by a large spectrum of diseases. Their diversity is well known for immunologic pathways (IgE, non-IgE-mediated FAs) and natural history. Many other factors and patient characteristics are involved including type of food, exposure route, allergic comorbidities, gender, racial and ethnic backgrounds, cofactors and health conditions. Food allergen components and sensitization profiles are also involved in FA phenotypes. A new approach to chronic disorders based on the identification of phenotypes through extensive knowledge of all the complex components is also applicable to FAs and could lead towards integrative care management. Diagnostic biomarkers for FAs are emerging which also contribute to better care modalities. The aim of this article was to highlight current knowledge regarding the phenotypic diversity of FA. This review will focus on IgE-mediated FAs and how identifying phenotypes may help to better understand the pathophysiological complexity, improve diagnosis and lead to personalized treatment strategies.

Circulating CXCR5+CD4+ T cells participate in the IgE accumulation in allergic asthma

The pathogenesis of allergic asthma is primarily characterized by abnormality in immunoglobin(Ig)E pathway, suggesting a possible role for follicular helper T cells (Tfh) in the genesis of excessive IgE accumulation. The blood chemokine (C-X-C motif) receptor 5 (CXCR)5⁺CD4⁺ T cells, known as "circulating" Tfh, share common functional characteristics with Tfh cells from germinal centers. The aim of this study was to determine the phenotypes and functions of circulating CXCR5⁺CD4⁺ T cells in allergic asthmatics. Here we found the frequency of the circulating CXCR5⁺CD4⁺ T cells was raised in allergic asthma compared with healthy control (HC). Phenotypic assays showed that activated circulating CXCR5⁺CD4⁺ T cells display the key features of Tfh cells, including invariably coexpressed programmed cell death (PD)-1 and inducible costimulator (ICOS). The frequency of interleukin IL-4⁺-, IL-21⁺-producing CXCR5⁺CD4⁺ T cells was increased in allergic asthma patients compared with HC. Furthermore, sorted circulating CXCR5⁺CD4⁺ T cells from allergic asthma patients boosted IgE production in coculture assay which could be inhibited by IL-4 or IL-21 blockage. Interestingly, IL-4⁺-, IL-21⁺-CXCR5⁺CD4⁺ T cells positively correlated with total IgE in the blood. Our data indicated that circulating CXCR5⁺CD4⁺ T cells may have a significant role in facilitating IgE production in allergic asthma patients.

Post-transplantation Development of Food Allergies

PURPOSE OF REVIEW

The development of food allergies is increasingly being recognized as a post-solid organ transplant complication. In this article, we review the spectrum of post-transplant food allergy development and the proposed mechanisms for de novo food allergies and the clinical significance they pose.

RECENT FINDINGS

The development of new food allergies is disproportionately associated with pediatric liver transplants, where it occurs in up to 38% of select populations. The mechanism of food allergy development is not completely understood; however, it is likely promoted by unbalanced immune suppression. De novo food allergy development is a common complication of solid organ transplants with the highest risk occurring in pediatric liver transplant recipients. There are likely multiple mechanisms for food allergy development including passive transfer of membrane-bound IgE and lymphocytes from donor to recipient, as well as loss of food tolerance and active development of new food allergies. The optimal management of food allergies following organ transplants has not been well researched but may include changing the immune suppression regimen if the food allergy does not resolve without intervention.

Developments in the field of allergy mechanisms in 2015 through the eyes of Clinical & Experimental Allergy

In the first of two papers we described the development in the field of allergy mechanisms as described by Clinical and Experimental Allergy in 2015. Experimental models of allergic disease, basic mechanisms, clinical mechanisms and allergens are all covered. A second paper will cover clinical aspects.

T follicular regulatory cells in mice and men

It has long been known that CD4 T cells are necessary to provide help to B cells, triggering a germinal centre (GC) reaction where affinity maturation and isotype switching occur. However, the nature of the dedicated CD4 helper T cells, known as T follicular helper (Tfh), was only recently described. Here, we review the biology and function of the recently described T follicular regulatory (Tfr) cells, another CD4 T-cell population also found within GCs but with regulatory function and characteristics. Tfr cells have been identified in mice and humans as simultaneously presenting characteristics of T follicular cells (namely CXCR5 expression) and regulatory T cells (including Foxp3 expression). These Tfr cells have been implicated in the regulation of the magnitude of the GC reaction, as well as in protection from immune-mediated pathology.

T follicular helper (Tfh ) cells in normal immune responses and in allergic disorders

Follicular helper T cells (Tfh ) are located within germinal centers of lymph nodes. Cognate interaction between Tfh , B cells, and IL-21 drives B cells to proliferate and differentiate into plasma cells thereby leading to antibody production. Tfh cells and IL-21 are involved in infectious and autoimmune diseases, immunodeficiencies, vaccination, and cancer. Human peripheral blood CXCR5(+) CD4(+) T cells comprise different subsets of Tfh -like cells. Despite the importance of the IgE response in the pathogenesis of allergic disorders, little is known about the role of follicular and blood Tfh cells and IL-21 in human and experimental allergic disease. Here, we review recent advances regarding the phenotypic and functional characteristics of both follicular and blood Tfh cells and of the IL-21/IL-21R system in the context of allergic disorders.