Leucocyte adhesion deficiency presenting as a chronic ileocolitis

Loss of β2-integrin function results in metabolic reprogramming of dendritic cells, leading to increased dendritic cell functionality and anti-tumor responses

Dendritic cells (DCs) are the main antigen presenting cells of the immune system and are essential for anti-tumor responses. DC-based immunotherapies are used in cancer treatment, but their functionality is not optimized and their clinical efficacy is currently limited. Approaches to improve DC functionality in anti-tumor immunity are therefore required. We have previously shown that the loss of β2-integrin-mediated adhesion leads to epigenetic reprogramming of bone marrow-derived DCs (BM-DCs), resulting in an increased expression of costimulatory markers (CD86, CD80, and CD40), cytokines (IL-12) and the chemokine receptor CCR7. We now show that the loss of β2-integrin-mediated adhesion of BM-DCs also leads to a generally suppressed metabolic profile, with reduced metabolic rate, decreased ROS production, and lowered glucose uptake in cells. The mRNA levels of glycolytic enzymes and glucose transporters were reduced, indicating transcriptional regulation of the metabolic phenotype. Surprisingly, although signaling through a central regulator of immune cell metabolisms, the mechanistic target of rapamycin (mTOR), was increased in BM-DCs with dysfunctional integrins, rapamycin treatment revealed that mTOR signaling was not involved in suppressing DC metabolism. Instead, bioinformatics and functional analyses showed that the Ikaros transcription factor may be involved in regulating the metabolic profile of non-adhesive DCs. Inversely, we found that induction of metabolic stress through treatment of cells with low levels of an inhibitor of glycolysis, 2-deoxyglucose (2DG), led to increased BM-DC activation. Specifically, 2DG treatment led to increased levels of Il-12 and Ccr7 mRNA, increased production of IL-12, increased levels of cell surface CCR7 and increased in vitro migration and T cell activation potential. Furthermore, 2DG treatment led to increased histone methylation in cells (H3K4me3, H3K27me3), indicating metabolic reprogramming. Finally, metabolic stress induced by 2DG treatment led to improved BM-DC-mediated anti-tumor responses in vivo in a melanoma cancer model, B16-OVA. In conclusion, our results indicate a role for β2-integrin-mediated adhesion in regulating a novel type of metabolic reprogramming of DCs and DC-mediated anti-tumor responses, which may be targeted to enhance DC-mediated anti-tumor responses in cancer immunotherapy.

Pharmacologic Management of Monogenic and Very Early Onset Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD) is treated with a variety of immunomodulating and immunosuppressive therapies; however, for the majority of cases, these therapies are not targeted for specific disease phenotypes. Monogenic IBD with causative genetic defect is the exception and represents a disease cohort where precision therapeutics can be applied. With the advent of rapid genetic sequencing platforms, these monogenic immunodeficiencies that cause inflammatory bowel disease are increasingly being identified. This subpopulation of IBD called very early onset inflammatory bowel disease (VEO-IBD) is defined by an age of onset of less than six years of age. Twenty percent of VEO-IBDs have an identifiable monogenic defect. The culprit genes are often involved in pro-inflammatory immune pathways, which represent potential avenues for targeted pharmacologic treatments. This review will provide an overview of the current state of disease-specific targeted therapies, as well as empiric treatment for undifferentiated causes of VEO-IBD.

Linking Genetic Diagnosis to Therapeutic Approach in Very Early Onset Inflammatory Bowel Disease: Pharmacologic Considerations

Very early onset inflammatory bowel disease (VEO-IBD) is diagnosed in children < 6 years of age, and in rare cases may be due to an identifiable monogenic cause. Recent advances in genetic testing have allowed for more accurate diagnosis, with as many as 100 genes now known to be associated with monogenic inflammatory bowel disease. These genes are involved in many immune pathways and thus may represent potential avenues for targeted precision medicine with pharmacologic treatments aimed at these. This review describes the broad classifications of monogenic disorders known to cause VEO-IBD, as well as empiric and disease-specific medical therapies. These include immune-modulating or immunosuppressant medications, nutritional therapy, surgery, and hematopoietic stem cell transplantation. We aim to provide an overview of the current state of targeted therapy for VEO-IBD.

Understanding the Role of LFA-1 in Leukocyte Adhesion Deficiency Type I (LAD I): Moving towards Inflammation?

LFA-1 (Lymphocyte function-associated antigen-1) is a heterodimeric integrin (CD11a/CD18) present on the surface of all leukocytes; it is essential for leukocyte recruitment to the site of tissue inflammation, but also for other immunological processes such as T cell activation and formation of the immunological synapse. Absent or dysfunctional expression of LFA-1, caused by mutations in the ITGB2 (integrin subunit beta 2) gene, results in a rare immunodeficiency syndrome known as Leukocyte adhesion deficiency type I (LAD I). Patients suffering from severe LAD I present with recurrent infections of the skin and mucosa, as well as inflammatory symptoms complicating the clinical course of the disease before and after allogeneic hematopoietic stem cell transplantation (alloHSCT); alloHSCT is currently the only established curative treatment option. With this review, we aim to provide an overview of the intrinsic role of inflammation in LAD I.

β2-Integrin Adhesion Regulates Dendritic Cell Epigenetic and Transcriptional Landscapes to Restrict Dendritic Cell Maturation and Tumor Rejection

Dendritic cells (DC), the classic antigen-presenting cells of the immune system, switch from an adhesive, phagocytic phenotype in tissues, to a mature, nonadhesive phenotype that enables migration to lymph nodes to activate T cells and initiate antitumor responses. Monocyte-derived DCs are used in cancer immunotherapy, but their clinical efficacy is limited. Here, we show that cultured bone marrow-derived DCs (BM-DC) expressing dysfunctional β2-integrin adhesion receptors displayed enhanced tumor rejection capabilities in B16.OVA and B16-F10 melanoma models. This was associated with an increased CD8⁺ T-cell response. BM-DCs expressing dysfunctional β2-integrins or manipulated to disrupt integrin adhesion or integrin/actin/nuclear linkages displayed spontaneous maturation in ex vivo cultures (increased costimulatory marker expression, IL12 production, and 3D migration capabilities). This spontaneous maturation was associated with an altered DC epigenetic/transcriptional profile, including a global increase in chromatin accessibility and H3K4me3/H3K27me3 histone methylation. Genome-wide analyses showed that H3K4me3 methylation was increased on DC maturation genes, such as CD86, Il12, Ccr7, and Fscn1, and revealed a role for a transcription factor network involving Ikaros and RelA in the integrin-regulated phenotype of DCs. Manipulation of the integrin-regulated epigenetic landscape in wild-type ex vivo-cultured BM-DCs enhanced their functionality in tumor rejection in vivo. Thus, β2-integrin-mediated adhesion to the extracellular environment plays an important role in restricting DC maturation and antitumor responses through regulation of the cellular epigenetic and transcriptional landscape. Targeting β2-integrins could therefore be a new strategy to improve the performance of current DC-based cancer immunotherapies.

Dendritic cell integrin expression patterns regulate inflammation in the rheumatoid arthritis joint

Objectives

Immune dysregulation contributes to the development of RA. Altered surface expression patterns of integrin adhesion receptors by immune cells is one mechanism by which this may occur. We investigated the role of β₂ integrin subunits CD11a and CD11b in dendritic cell (DC) subsets of RA patients.

Methods

Total β₂ integrin subunit expression and its conformation (‘active’ vs ‘inactive’ state) were quantified in DC subsets from peripheral blood (PB) and SF of RA patients as well as PB from healthy controls. Ex vivo stimulation of PB DC subsets and in vitro-generated mature and tolerogenic monocyte-derived DCs (moDCs) were utilized to model the clinical findings. Integrin subunit contribution to DC function was tested by analysing clustering and adhesion, and in co-cultures to assess T cell activation.

Results

A significant reduction in total and active CD11a expression in DCs in RA SF compared with PB and, conversely, a significant increase in CD11b expression was found. These findings were modelled in vitro using moDCs: tolerogenic moDCs showed higher expression of active CD11a and reduced levels of active CD11b compared with mature moDCs. Finally, blockade of CD11b impaired T cell activation in DC–T cell co-cultures.

Conclusion

For the first time in RA, we show opposing expression of CD11a and CD11b in DCs in environments of inflammation (CD11a^low/CD11b^high) and steady state/tolerance (CD11a^high/CD11b^low), as well as a T cell stimulatory role for CD11b. These findings highlight DC integrins as potential novel targets for intervention in RA.

Very Early Onset Inflammatory Bowel Disease: A Clinical Approach With a Focus on the Role of Genetics and Underlying Immune Deficiencies

Very early onset inflammatory bowel disease (VEO-IBD) is defined as IBD presenting before 6 years of age. When compared with IBD diagnosed in older children, VEO-IBD has some distinct characteristics such as a higher likelihood of an underlying monogenic etiology or primary immune deficiency. In addition, patients with VEO-IBD have a higher incidence of inflammatory bowel disease unclassified (IBD-U) as compared with older-onset IBD. In some populations, VEO-IBD represents the age group with the fastest growing incidence of IBD. There are contradicting reports on whether VEO-IBD is more resistant to conventional medical interventions. There is a strong need for ongoing research in the field of VEO-IBD to provide optimized management of these complex patients. Here, we provide an approach to diagnosis and management of patients with VEO-IBD. These recommendations are based on expert opinion from members of the VEO-IBD Consortium (www.VEOIBD.org). We highlight the importance of monogenic etiologies, underlying immune deficiencies, and provide a comprehensive description of monogenic etiologies identified to date that are responsible for VEO-IBD.

Gastrointestinal Disorders Associated with Primary Immunodeficiency Diseases

There are now 354 inborn errors of immunity (primary immunodeficiency diseases (PIDDs)) with 344 distinct molecular etiologies reported according to the International Union of Immunological Sciences (IUIS) (Clin Gastroenterol Hepatol 11: p. 1050-63, 2013, Semin Gastrointest Dis 8: p. 22-32, 1997, J Clin Immunol 38: p. 96-128, 2018). Using the IUIS document as a reference and cross-checking PubMed ( www.ncbi.nlm.nih.pubmed.gov ), we found that approximately one third of the 354 diseases of impaired immunity have a gastrointestinal component [J Clin Immunol 38: p. 96-128, 2018]. Often, the gastrointestinal symptomatology and pathology is the heralding sign of a PIDD; therefore, it is important to recognize patterns of disease which may manifest along the gastrointestinal tract as a more global derangement of immune function. As such, holistic consideration of immunity is warranted in patients with clinically significant gastrointestinal disease. Here, we discuss the manifold presentations and GI-specific complications of PIDDs which could lead patients to seek advice from a variety of clinician specialists. Often, patients with these medical problems will engage general pediatricians, surgeons, gastroenterologists, rheumatologists, and clinical immunologists among others. Following delineation of the presenting concern, accurate and often molecular diagnosis is imperative and a multi-disciplinary approach warranted for optimal management. In this review, we will summarize the current state of understanding of PIDD gastrointestinal disease involvement. We will do so by focusing upon gastrointestinal disease categories (i.e., inflammatory, diarrhea, nodular lymphoid hyperplasia, liver/biliary tract, structural disease, and oncologic disease) with an intent to aid the healthcare provider who may encounter a patient with an as-yet undiagnosed PIDD who presents initially with a gastrointestinal symptom, sign, or problem.

β2 Integrins-Multi-Functional Leukocyte Receptors in Health and Disease

β2 integrins are heterodimeric surface receptors composed of a variable α (CD11a-CD11d) and a constant β (CD18) subunit and are specifically expressed by leukocytes. The α subunit defines the individual functional properties of the corresponding β2 integrin, but all β2 integrins show functional overlap. They mediate adhesion to other cells and to components of the extracellular matrix (ECM), orchestrate uptake of extracellular material like complement-opsonized pathogens, control cytoskeletal organization, and modulate cell signaling. This review aims to delineate the tremendous role of β2 integrins for immune functions as exemplified by the phenotype of LAD-I (leukocyte adhesion deficiency 1) patients that suffer from strong recurrent infections. These immune defects have been largely attributed to impaired migratory and phagocytic properties of polymorphonuclear granulocytes. The molecular base for this inherited disease is a functional impairment of β2 integrins due to mutations within the CD18 gene. LAD-I patients are also predisposed for autoimmune diseases. In agreement, polymorphisms within the CD11b gene have been associated with autoimmunity. Consequently, β2 integrins have received growing interest as targets in the treatment of autoimmune diseases. Moreover, β2 integrin activity on leukocytes has been implicated in tumor development.

Genetics on early onset inflammatory bowel disease: An update

Inflammatory bowel disease (IBD) is more common in adults than in children. Onset of IBD before 17 years of age is referred as pediatric onset IBD and is further categorized as very early onset IBD (VEO-IBD) for children who are diagnosed before 6 years of age, infantile IBD who had the disease before 2 years of age and neonatal onset IBD for children less than 28 days of life. Children presenting with early onset disease may have a monogenic basis. Knowledge and awareness of the clinical manifestations facilitates early evaluation and diagnosis. Next generation sequencing is helpful in making the genetic diagnosis. Treatment of childhood IBD is difficult; targeted therapies and hematopoietic stem cell transplantation form the mainstay. In this review we aim to summarize the genetic defects associated with IBD phenotype. We describe genetic location and functions of various genetic defect associated with VEO-IBD with their key clinical manifestations. We also provide clinical clues to suspect these conditions and approaches to the diagnosis of these disorders and suitable treatment options.

Leukocyte adhesion defect: Where do we stand circa 2019?

Migration of polymorphonuclear leukocytes from bloodstream to the site of inflammation is an important event required for surveillance of foreign antigens. This trafficking of leukocytes from bloodstream to the tissue occurs in several distinct steps and involves several adhesion molecules. Defect in adhesion of leukocytes to vascular endothelium affecting their subsequent migration to extravascular space gives rise to a group of rare primary immunodeficiency diseases (PIDs) known as Leukocyte Adhesion Defects (LAD). Till date, four classes of LAD are discovered with LAD I being the most common form. LAD I is caused by loss of function of common chain, cluster of differentiation (CD)18 of β2 integrin family. These patients suffer from life-threatening bacterial infections and in its severe form death usually occurs in childhood without bone marrow transplantation. LAD II results from a general defect in fucose metabolism. These patients suffer from less severe bacterial infections and have growth and mental retardation. Bombay blood group phenotype is also observed in these patients. LAD III is caused by abnormal integrin activation. LAD III patients suffer from severe bacterial and fungal infections. Patients frequently show delayed detachment of umbilical cord, impaired wound healing and increased tendency to bleed. LAD IV is the most recently described class. It is caused by defects in β2 and α4β1 integrins which impairs lymphocyte adhesion. LAD IV patients have monogenic defect in cystic-fibrosis-transmembrane-conductance-regulator (CFTR) gene, resulting in cystic fibrosis. Pathophysiology and genetic etiology of all LAD syndromes are discussed in detail in this paper.

Controlling Gut Inflammation by Restoring Anti-Inflammatory Pathways in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is caused by a dysregulated immune response against normal components of the intestinal microflora combined with defective functioning of anti-inflammatory pathways. Currently, all therapies approved for IBD manipulate the immune system by inhibiting pro-inflammatory mechanisms, such as tumor necrosis factor-α, gut-homing α4β7 integrin, interleukin-12/interleukin-23, and Janus kinases. However, some IBD patients are non-responders to these drugs, which are also associated with serious side effects. Thus, it has been hypothesized that therapies aimed at restoring anti-inflammatory signals, by exploiting the tolerogenic potential of cytokines (interleukin-10, transforming growth factor-β, granulocyte macrophage colony-stimulating factor), immune cells (regulatory T cells, tolerogenic dendritic cells), or mesenchymal stem cells, might offer promising results in terms of clinical efficacy with fewer side effects. In this review, we provide new insights into putative novel treatments aimed at restoring anti-inflammatory signaling pathways in IBD.

Beta2-Integrins and Interacting Proteins in Leukocyte Trafficking, Immune Suppression, and Immunodeficiency Disease

Beta2-integrins are complex leukocyte-specific adhesion molecules that are essential for leukocyte (e.g., neutrophil, lymphocyte) trafficking, as well as for other immunological processes such as neutrophil phagocytosis and ROS production, and T cell activation. Intriguingly, however, they have also been found to negatively regulate cytokine responses, maturation, and migratory responses in myeloid cells such as macrophages and dendritic cells, revealing new, and unexpected roles of these molecules in immunity. Because of their essential role in leukocyte function, a lack of expression or function of beta2-integrins causes rare immunodeficiency syndromes, Leukocyte adhesion deficiency type I, and type III (LAD-I and LAD-III). LAD-I is caused by reduced or lost expression of beta2-integrins, whilst in LAD-III, beta2-integrins are expressed but dysfunctional because a major integrin cytoplasmic regulator, kindlin-3, is mutated. Interestingly, some LAD-related phenotypes such as periodontitis have recently been shown to be due to an uncontrolled inflammatory response rather than to an uncontrolled infection, as was previously thought. This review will focus on the recent advances concerning the regulation and functions of beta2-integrins in leukocyte trafficking, immune suppression, and immune deficiency disease.

Macrophage β2-Integrins Regulate IL-22 by ILC3s and Protect from Lethal Citrobacter rodentium-Induced Colitis

β2-integrins promote neutrophil recruitment to infected tissues and are crucial for host defense. Neutrophil recruitment is defective in leukocyte adhesion deficiency type-1 (LAD1), a condition caused by mutations in the CD18 (β2-integrin) gene. Using a model of Citrobacter rodentium (CR)-induced colitis, we show that CD18-/- mice display increased intestinal damage and systemic bacterial burden, compared to littermate controls, ultimately succumbing to infection. This phenotype is not attributed to defective neutrophil recruitment, as it is shared by CXCR2-/- mice that survive CR infection. CR-infected CD18-/- mice feature prominent upregulation of IL-17 and downregulation of IL-22. Exogenous IL-22 administration, but not endogenous IL-17 neutralization, protects CD18-/- mice from lethal colitis. β2-integrin expression on macrophages is mechanistically linked to Rac1/ROS-mediated induction of noncanonical-NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3) inflammasome-dependent IL-1β production, which promotes ILC3-derived IL-22. Therefore, β2-integrins are required for protective IL-1β-dependent IL-22 responses in colitis, and the identified mechanism may underlie the association of human LAD1 with colitis.

Early-onset inflammatory bowel disease as a model disease to identify key regulators of immune homeostasis mechanisms

Rare, monogenetic diseases present unique models to dissect gene functions and biological pathways, concomitantly enhancing our understanding of the etiology of complex (and often more common) traits. Although inflammatory bowel disease (IBD) is a generally prototypic complex disease, it can also manifest in an early-onset, monogenic fashion, often following Mendelian modes of inheritance. Recent advances in genomic technologies have spurred the identification of genetic defects underlying rare, very early-onset IBD (VEO-IBD) as a disease subgroup driven by strong genetic influence, pinpointing key players in the delicate homeostasis of the immune system in the gut and illustrating the intimate relationships between bowel inflammation, systemic immune dysregulation, and primary immunodeficiency with increased susceptibility to infections. As for other human diseases, it is likely that adult-onset diseases may represent complex diseases integrating the effects of host genetic susceptibility and environmental triggers. Comparison of adult-onset IBD and VEO-IBD thus provides beautiful models to investigate the relationship between monogenic and multifactorial/polygenic diseases. This review discusses the present and novel findings regarding monogenic IBD as well as key questions and future directions of IBD research.

Recent Advance in Very Early Onset Inflammatory Bowel Disease

Recent studies on pediatric inflammatory bowel disease (IBD) have revealed that early-onset IBD has distinct phenotypic differences compared with adult-onset IBD. In particular, very early-onset IBD (VEO-IBD) differs in many aspects, including the disease type, location of the lesions, disease behavior, and genetically attributable risks. Several genetic defects that disturb intestinal epithelial barrier function or affect immune function have been noted in these patients from the young age groups. In incidence of pediatric IBD in Korea has been increasing since the early 2000s. Neonatal or infantile-onset IBD develops in less than 1% of pediatric patients. Children with "neonatal IBD" or "infantile-onset IBD" have higher rates of affected first-degree relatives, severe disease course, and a high rate of resistance to immunosuppressive treatment. The suspicion of a monogenic cause of VEO-IBD was first confirmed by the discovery of mutations in the genes encoding the interleukin 10 (IL-10) receptors that cause impaired IL-10 signaling. Patients with such mutations typically presented with perianal fistulae, shows a poor response to medical management, and require early surgical interventions in the first year of life. To date, 60 monogenic defects have been identified in children with IBD-like phenotypes. The majority of monogenic defects presents before 6 years of age, and many present before 1 year of age. Next generation sequencing could become an important diagnostic tool in children with suspected genetic defects especially in children with VEO-IBD with severe disease phenotypes. VEO-IBD is a phenotypically and genetically distinct disease entity from adult-onset or older pediatric IBD.

Recent advance in very early-onset inflammatory bowel disease

Recent studies on pediatric inflammatory bowel disease (IBD) have revealed that early-onset IBD has distinct phenotypic differences compared with adult-onset IBD. In particular, very early-onset IBD (VEO-IBD) differs in many aspects, including the disease type, location of the lesions, disease behavior, and genetically attributable risks. Neonatal or infantile-onset IBD develops in less than 1% of pediatric patients. Children with infantile-onset IBD have high rates of affected first-degree relatives and severe disease course. The suspicion of a monogenic cause of VEO-IBD was first confirmed by the discovery of mutations in the genes encoding the interleukin 10 (IL-10) receptors that cause impaired IL-10 signaling. Patients with such mutations typically presented with perianal fistulae, shows a poor response to medical management, and require early surgical interventions in the first year of life. To date, 60 monogenic defects have been identified in children with IBD-like phenotypes. The majority of monogenic defects presents before 6 years of age, and many present before 1 year of age. Next generation sequencing could become an important diagnostic tool in children with suspected genetic defects especially in children with VEO-IBD with severe disease phenotypes. VEO-IBD is a phenotypically and genetically distinct disease entity from adult-onset or older pediatric IBD.

Analysis of Genes Associated With Monogenic Primary Immunodeficiency Identifies Rare Variants in XIAP in Patients With Crohn's Disease

BACKGROUND & AIMS

A few rare monogenic primary immunodeficiencies (PIDs) are characterized by chronic intestinal inflammation that resembles Crohn's disease (CD). We investigated whether 23 genes associated with 10 of these monogenic disorders contain common, low-frequency, or rare variants that increase risk for CD.

METHODS

Common and low frequency variants in 1 Mb loci centered on the candidate genes were analyzed using meta-data corresponding to genotypes of approximately 17,000 patients with CD or without CD (controls) in Europe. The contribution of rare variants was assessed by high-throughput sequencing of 4750 individuals, including 660 early-onset and/or familial cases among the 2390 patients with CD. Variants were expressed from vectors in SW480 or HeLa cells and functions of their products were analyzed in immunofluorescence, luciferase, immunoprecipitation, and immunoblot assays.

RESULTS

We reproduced the association of the interleukin 10 locus with CD (P = .007), although none of the significantly associated variants modified the coding sequence of interleukin 10. We found XIAP to be significantly enriched for rare coding mutations in patients with CD vs controls (P = .02). We identified 4 previously unreported missense variants associated with CD. Variants in XIAP cause the PID X-linked lymphoproliferative disease type 2, yet none of the carriers of these variants had all the clinical features of X-linked lymphoproliferative disease type 2. Identified XIAP variants S123N, R233Q, and P257A were associated with an impaired activation of NOD2 signaling after muramyl dipeptide stimulation.

CONCLUSIONS

In a systematic analysis of variants in 23 PID-associated genes, we confirmed the association of variants in XIAP with CD. Further screenings for CD-associated variants and analyses of their functions could increase our understanding of the relationship between PID-associated genes and CD pathogenesis.

β2 Integrins As Regulators of Dendritic Cell, Monocyte, and Macrophage Function

Emerging evidence suggests that the β₂ integrin family of adhesion molecules have an important role in suppressing immune activation and inflammation. β₂ integrins are important adhesion and signaling molecules that are exclusively expressed on leukocytes. The four β₂ integrins (CD11a, CD11b, CD11c, and CD11d paired with the β₂ chain CD18) play important roles in regulating three key aspects of immune cell function: recruitment to sites of inflammation; cell-cell contact formation; and downstream effects on cellular signaling. Through these three processes, β₂ integrins both contribute to and regulate immune responses. This review explores the pro- and anti-inflammatory effects of β₂ integrins in monocytes, macrophages, and dendritic cells and how they influence the outcome of immune responses. We furthermore discuss how imbalances in β₂ integrin function can have far-reaching effects on mounting appropriate immune responses, potentially influencing the development and progression of autoimmune and inflammatory diseases. Therapeutic targeting of β₂ integrins, therefore, holds enormous potential in exploring treatment options for a variety of inflammatory conditions.

Nonclassic Inflammatory Bowel Disease in Young Infants: Immune Dysregulation, Polyendocrinopathy, Enteropathy, X-Linked Syndrome, and Other Disorders

This article discusses non-classical forms of inflammatory bowel disease (IBD) mainly occurs in infants and very young children. Defects in every aspect of the immune system, such as neutrophils, T-cell and B-cell lymphocytes, and macrophages are associated with IBD in infants. Also, non lympho-hematopoietic defects with primary defects in enterocytes can also lead to IBD-like manifestations. Clinical vignettes are presented and the genetic origins and possible management strategies are outlined. Early evaluation of these patients is important because identification of underlying immune defects would facilitate the use of better-targeted therapy for the specific genetic defect.

The diagnostic approach to monogenic very early onset inflammatory bowel disease

Patients with a diverse spectrum of rare genetic disorders can present with inflammatory bowel disease (monogenic IBD). Patients with these disorders often develop symptoms during infancy or early childhood, along with endoscopic or histological features of Crohn's disease, ulcerative colitis, or IBD unclassified. Defects in interleukin-10 signaling have a Mendelian inheritance pattern with complete penetrance of intestinal inflammation. Several genetic defects that disturb intestinal epithelial barrier function or affect innate and adaptive immune function have incomplete penetrance of the IBD-like phenotype. Several of these monogenic conditions do not respond to conventional therapy and are associated with high morbidity and mortality. Due to the broad spectrum of these extremely rare diseases, a correct diagnosis is frequently a challenge and often delayed. In many cases, these diseases cannot be categorized based on standard histological and immunologic features of IBD. Genetic analysis is required to identify the cause of the disorder and offer the patient appropriate treatment options, which include medical therapy, surgery, or allogeneic hematopoietic stem cell transplantation. In addition, diagnosis based on genetic analysis can lead to genetic counseling for family members of patients. We describe key intestinal, extraintestinal, and laboratory features of 50 genetic variants associated with IBD-like intestinal inflammation. In addition, we provide approaches for identifying patients likely to have these disorders. We also discuss classic approaches to identify these variants in patients, starting with phenotypic and functional assessments that lead to analysis of candidate genes. As a complementary approach, we discuss parallel genetic screening using next-generation sequencing followed by functional confirmation of genetic defects.

Loss of beta2-integrin-mediated cytoskeletal linkage reprogrammes dendritic cells to a mature migratory phenotype

The actin cytoskeleton has been reported to restrict signaling in resting immune cells. Beta2-integrins, which mediate adhesion and cytoskeletal organization, are emerging as negative regulators of myeloid cell-mediated immune responses, but the molecular mechanisms involved are poorly understood. Here, we show that loss of the interaction between beta2-integrins and kindlin-3 abolishes the actin-linkage of integrins and the GM-CSF receptor in dendritic cells. This leads to increased GM-CSF receptor/Syk signaling, and to the induction of a transcriptional program characteristic of mature, migratory dendritic cells, accumulation of migratory dendritic cells in lymphoid organs, and increased Th1 immune responses in vivo. We observe increased GM-CSF responses and increased survival in neutrophils where the interaction between integrin and the cytoskeleton is disrupted. Thus, ligand-reinforced beta2-integrin tail interactions restrict cytokine receptor signaling, survival, maturation and migration in myeloid cells and thereby contribute to immune homeostasis in vivo.

Successful anti-TNF-α treatment in a girl with LAD-1 disease and autoimmune manifestations

Leukocyte adhesion deficiency type 1 (LAD-1) is an autosomal recessive disorder, caused by the absence or reduced expression of the beta-2 integrins on granulocytes, and characterized by the inability of these cells to emigrate from the bloodstream towards the sites of tissue inflammation. A twelve-year-old girl with a diagnosis of LAD-1 syndrome and recurrent skin and mucosal infections since birth, presented with a two week history of fever, abdominal pain, vomiting, weight loss and polyarthralgia. She underwent an exploratory laparotomy with the finding of inflamed terminal ileum and colon and a normal appendix. Colonoscopy and videocapsule endoscopy showed multiple ileal and colonic mucosal ulcerations, which were compatible with inflammatory bowel disease, confirmed on histological examination. Given the lack of response to conventional therapy (prednisone and mesalamine), a monoclonal anti-TNF-α antibody was started at a dosage of 5 mg/kg at weeks 0,2,4,6 and then every 8 weeks. We observed a significant improvement of all clinical and laboratory parameters after the first weeks of therapy. Five months later, we anticipated the drug's administration every 5 weeks because of a precocious recurrence of symptoms. After 30 months of treatment no relapse nor any relevant side effects have been observed, and corticosteroids were withdrawn. Interestingly, our patient presented a small subset of CD18+ T cells, similarly to previously reported LAD-1 patients with mild phenotype, inflammatory bowel disease and CD18+ somatic revertant T cells. To the best of our knowledge, this is the first LAD-1 pediatric patient with inflammatory autoimmune complications who experienced a positive response to anti-TNF-α treatment.

Distinct chemokine signaling regulates integrin ligand specificity to dictate tissue-specific lymphocyte homing

Immune surveillance and host defense depend on the precisely regulated trafficking of lymphocytes. Integrin α4β7 mediates lymphocyte homing to the gut through its interaction with mucosal vascular address in cell adhesion molecule-1 (MAdCAM-1). α4β7 also binds vascular cell adhesion molecule-1 (VCAM-1), which is expressed in other tissues. To maintain the tissue specificity of lymphocyte homing, α4β7 must distinguish one ligand from the other. Here, we demonstrate that α4β7 is activated by different chemokines in a ligand-specific manner. CCL25 stimulation promotes α4β7-mediated lymphocyte adhesion to MAdCAM-1 but suppresses adhesion to VCAM-1, whereas CXCL10 stimulation has the opposite effect. Using separate pathways, CCL25 and CXCL10 stimulate differential phosphorylation states of the β7 tail and distinct talin and kindlin-3 binding patterns, resulting in different binding affinities of MAdCAM-1 and VCAM-1 to α4β7. Thus, our findings provide a mechanism for lymphocyte traffic control through the unique ligand-specific regulation of integrin adhesion by different chemokines.

Monogenic diseases associated with intestinal inflammation: implications for the understanding of inflammatory bowel disease

Inflammatory bowel disease (IBD), encompassing Crohn's disease and ulcerative colitis, has multifactorial aetiology with complex interactions between genetic and environmental factors. Over 150 genetic loci are associated with IBD. The genetic contribution of the majority of those loci towards explained heritability is low. Recent studies have reported an increasing spectrum of human monogenic diseases that can present with IBD-like intestinal inflammation. A substantial proportion of patients with those genetic defects present with very early onset of intestinal inflammation. The 40 monogenic defects with IBD-like pathology selected in this review can be grouped into defects in intestinal epithelial barrier and stress response, immunodeficiencies affecting granulocyte and phagocyte activity, hyper- and autoinflammatory disorders as well as defects with disturbed T and B lymphocyte selection and activation. In addition, there are defects in immune regulation affecting regulatory T cell activity and interleukin (IL)-10 signalling. Related to the variable penetrance of the IBD-like phenotype, there is a likely role for modifier genes and gene-environment interactions. Treatment options in this heterogeneous group of disorders range from anti-inflammatory and immunosuppressive therapy to blockade of tumour necrosis factor α and IL-1β, surgery, haematopoietic stem cell transplantation or gene therapy. Understanding of prototypic monogenic 'orphan' diseases cannot only provide treatment options for the affected patients but also inform on immunological mechanisms and complement the functional understanding of the pathogenesis of IBD.

Adult siblings with homozygous G6PC3 mutations expand our understanding of the severe congenital neutropenia type 4 (SCN4) phenotype

Background

Severe congenital neutropenia type 4 (SCN4) is an autosomal recessive disorder caused by mutations in the third subunit of the enzyme glucose-6-phosphatase (G6PC3). Its core features are congenital neutropenia and a prominent venous skin pattern, and affected individuals have variable birth defects. Oculocutaneous albinism type 4 (OCA4) is caused by autosomal recessive mutations in SLC45A2.

Methods

We report a sister and brother from Newfoundland, Canada with complex phenotypes. The sister was previously reported by Cullinane et al., 2011. We performed homozygosity mapping, next generation sequencing and conventional Sanger sequencing to identify mutations that cause the phenotype in this family. We have also summarized clinical data from 49 previously reported SCN4 cases with overlapping phenotypes and interpret the medical histories of these siblings in the context of the literature.

Results

The siblings’ phenotype is due in part to a homozygous mutation in G6PC3, [c.829C > T, p.Gln277X]. Their ages are 38 and 37 years respectively and they are the oldest SCN4 patients published to date. Both presented with congenital neutropenia and later developed Crohn disease. We suggest that the latter is a previously unrecognized SCN4 manifestation and that not all affected individuals have an intellectual disability. The sister also has a homozygous mutation in SLC45A2, which explains her severe oculocutaneous hypopigmentation. Her brother carried one SLC45A2 mutation and was diagnosed with “partial OCA” in childhood.

Conclusions

This family highlights that apparently novel syndromes can in fact be caused by two known autosomal recessive disorders.

High levels of Crohn's disease-associated anti-microbial antibodies are present and independent of colitis in chronic granulomatous disease

Chronic granulomatous disease (CGD) and inflammatory bowel disease (IBD) have overlapping gastrointestinal manifestations. Serum antibodies to intestinal microbial antigens in IBD are thought to reflect a loss of tolerance in the setting of genetically encoded innate immune defects. CGD subjects studied here, with or without colitis, had considerably higher levels of ASCA IgA, ASCA IgG, anti-OmpC, anti-I2, and anti-CBir1, but absent to low pANCA, compared to IBD-predictive cutoffs. Higher antibody levels were not associated with a history of colitis. Except for higher ASCA IgG in subjects <18 years, antibody levels were not age-dependent. In comparison, 7 HIES subjects expressed negative to low antibody levels to all of these antigens; none had colitis. Our results suggest that markedly elevated levels of antimicrobial antibodies in CGD do not correlate with a history of colitis but may reflect a specific defect in innate immunity in the face of chronic antigenic stimulation.

The universe of immune deficiencies in Crohn's disease: a new viewpoint for an old disease?

Crohn's disease (CD) is generally considered a multifactorial disorder, since different genetic and environmental factors are thought to play a role in its pathogenesis. Recently, genome wide linkage studies allowed to identify the association of several loci with the increased risk of CD, although it is still unclear how they interact with environmental factors in causing the disease. The fact that many CD-risk-related genes are involved in the function of phagocytes seems in agreement with the well known role of these cells in CD histopathology. Functional defects in cytokine production or in clearance of bacteria in CD patients have recently been reported. Growing evidence that CD could arise from primary phagocyte immunodeficiency is also coming from the study of cases with early onset in infancy. We review such evidences starting from selected cases and discuss the clinical implications of these findings.

Enteropathies of Infancy and Childhood

Intestinal biopsies constitute an ever-increasing portion of the pathologist's workload, accounting for nearly two-thirds of specimens accessioned yearly by the pathology department at The Children's Hospital of Philadelphia. The widespread use of endoscopy and gastrointestinal biopsies in current clinical practice presents the pathologist with a diversity of intestinal mucosal appearances corresponding to disease states of variable clinical severity, requiring close collaboration between clinician and pathologist for optimal interpretation. Many of the entities resulting in severe diarrhea of infancy have been recognized only in the last several decades, and although rare, the study of these disorders, especially when combined with the powerful methods of present-day genetics and molecular biology, has afforded important insights into enterocyte development and function, and intestinal immunity and tolerance. Other conditions once considered infrequent, such as celiac disease, have now been recognized to be much more common and can present with a wide range of pathologic features.

Characterization of 11 new cases of leukocyte adhesion deficiency type 1 with seven novel mutations in the ITGB2 gene

BACKGROUND

Leukocyte adhesion deficiency type 1 (LAD I) is an autosomal recessive disorder caused by mutations in the ITGB2 gene, encoding the beta2 integrin family. Severe recurrent infections, impaired wound healing, and periodontal diseases are the main features of disease.

METHODS

In order to investigate clinical and molecular manifestations of new LAD I cases, 11 patients diagnosed in one center during 7 years were studied. Patients were screened for the ITGB2 gene mutations, using polymerase chain reaction, followed by single-strand conformation polymorphism and sequencing.

RESULTS

The most common first presenting feature of the patients was omphalitis. The mean age of cord separation was 19.9 +/- 1 days. The most common clinical manifestations of the patients during the follow-up period included omphalitis, skin ulcers with poor healing, sepsis, and otitis media. During the follow-up, eight patients died. Eight homozygous changes, including seven novel mutations, were detected: two splicing (IVS4-6C>A, IVS7+1G>A), three missense (Asp128Tyr, Ala239Thr, and Gly716Ala), and three frameshift deletions (Asn282fsX41, Tyr382fsX9, and Lys636fsX22).

CONCLUSION

Our results indicate that different mutations underlie the development of LAD I. Definitive molecular diagnosis is valuable for genetic counseling and prenatal diagnosis. Regarding clinical presentations, it seems that omphalitis is the most consistent finding seen in LAD I infants.

Anti-TNFα antibody infliximab treatment for an infant with fistulising Crohn's disease

A female infant presented at the age of 4 weeks with dyschezia and bloody streaking of stools which did not improve on elemental formula for proposed cow's milk protein allergy. At 6 months of age perianal ulceration appeared which evolved into multiple fistulas opening into the perineum. A diagnosis of infantile Crohn's disease was made after colonoscopy and histopathology examination and exclusion of other conditions. An 8 week trial of total parenteral nutrition, in addition to corticosteroids, salazopyrine, metronidazole, and azathioprine failed to arrest deterioration of the perianal fistulas. Treatment with the anti-TNFα antibody infliximab was started at 5 mg/kg/dose at 9 months of age. She was given three doses at 0, 2, and 6 weeks, respectively. This resulted in significant healing of her fistulas and cessation of fistula output. This improvement was sustained at the time of last follow-up 10 months after treatment.

Inflammatory bowel disease in CGD reproduces the clinicopathological features of Crohn's disease

OBJECTIVES

Patients with chronic granulomatous disease (CGD), a rare congenital disorder characterized by defective neutrophil function, frequently develop an inflammatory bowel disease similar to Crohn's disease. The clinical presentations and concordance between the features of the bowel disease in these two conditions have never been formally evaluated.

METHODS

Retrospective case note analysis of all adult patients with CGD treated at a tertiary care hospital.

RESULTS

A total of 25 eligible patients were identified. Of these, 14 (56%) had experienced gastrointestinal symptoms in the preceding 3 years; and 11 (44%) had documented gastrointestinal inflammation not secondary to infection, manifesting throughout the alimentary canal including the upper gastrointestinal tract (45%), small intestine (27%), colon (73%), and rectum (73%). All had discontinuous inflammation and perianal involvement, and approximately half (55%) demonstrated epithelioid granulomata on histology. All patients fulfilled the Lennard-Jones criteria for the diagnosis of Crohn's disease. Therapeutic responses were observed in five patients to 5-aminosalicylates, and in individual patients to thalidomide, interferon-gamma, azathioprine, infliximab, and intestinal resection.

CONCLUSIONS

There are striking clinical and pathological resemblances between the bowel diseases observed in CGD and Crohn's disease, supporting the possibility of mechanistic similarities in their pathogenesis. Patients with CGD appear particularly prone to developing perianal disease.

Hematopoietic stem cell transplantation in a CD3 gamma-deficient infant with inflammatory bowel disease

Partial or total CD3 chain expression defects including CD3 gamma, epsilon, delta, and zeta chain are among the autosomally inherited SCID presenting with T-B+NK+ phenotype with lymphopenia. The clinical findings are generally severe in all except for CD3 gamma deficiency. Here we present a 10-month-old CD3 gamma deficient boy with IBD. The patient had suffered from intractable diarrhea, recurrent pulmonary infections and oral moniliasis since two months of age. Following the first allogeneic HSCT from his HLA-identical (6/6) sister after a reduced intensity regimen, a second transplantation was performed five months later. On day +19 after second transplantation, the CD3 TCR alpha/beta chain expression increased to 66% with development of full donor chimerism (98.6%). A significant improvement in diarrhea, perianal lesions, and rectal fistula was observed suggesting an improvement in inflammatory bowel disease. The patient died at home on day +50 with a sudden respiratory failure secondary to an undetermined infection. The case was interesting being the first reported case with SCID and inflammatory bowel disease who responded very well to HSCT by full recovery of intractable diarrhea, failure to thrive, laboratory findings, and improvement of fistula formation.

Phagocyte dysfunction and inflammatory bowel disease

Inflammatory bowel diseases are common chronic inflammatory disorders. The majority are idiopathic and can be broadly divided into Crohn's disease and ulcerative colitis. Their cause is unknown, but most hypotheses focus on a primary role for T-cell dysfunction. Conversely, there is a collection of congenital disorders of phagocyte function that result not only in immunodeficiency but also in noninfectious inflammatory bowel disease. In all cases, the latter is strikingly reminiscent of the clinical and pathological features of Crohn's disease. This coincides with recent work demonstrating that despite previous emphasis on adaptive immune dysfunction, patients with Crohn's disease actually possess an unusually weak acute innate inflammatory response. This review consolidates the literature on inflammatory bowel disease in congenital immunodeficiencies and considers the role of phagocyte dysfunction in Crohn's disease. Concepts about pathogenesis and treatment that can be carried across these disorders are also discussed.

[Gastrointestinal diseases in primary immunodeficiency disorders]

Gastrointestinal symptoms are common and often reveal primary immunodeficiency. Although they mimic gastrointestinal diseases observed in immunocompetent patients, there have diagnostic and therapeutic specificities that should be known for optimal management of these patients. This review describes the gastrointestinal diseases found in primary immunodeficiency and proposes some diagnostic and therapeutic strategies.

Reversion mutations in patients with leukocyte adhesion deficiency type-1 (LAD-1)

Leukocyte adhesion deficiency type-1 (LAD-1) is an autosomal recessive immunodeficiency caused by mutations in the beta2 integrin, CD18, that impair CD11/CD18 heterodimer surface expression and/or function. Absence of functional CD11/CD18 integrins on leukocytes, particularly neutrophils, leads to their incapacity to adhere to the endothelium and migrate to sites of infection. We studied 3 LAD-1 patients with markedly diminished neutrophil CD18 expression, each of whom had a small population of lymphocytes with normal CD18 expression (CD18(+)). These CD18(+) lymphocytes were predominantly cytotoxic T cells, with a memory/effector phenotype. Microsatellite analyses proved patient origin of these cells. Sequencing of T-cell subsets showed that in each patient one CD18 allele had undergone further mutation. Interestingly, all 3 patients were young adults with inflammatory bowel disease. Somatic reversions of inherited mutations in primary T-cell immunodeficiencies are typically associated with milder clinical phenotypes. We hypothesize that these somatic revertant CD18(+) cytotoxic T lymphocytes (CTLs) may have altered immune regulation. The discovery of 3 cases of reversion mutations in LAD-1 at one center suggests that this may be a relatively common event in this rare disease.

Crohn’s disease: Innate immunodeficiency?

In the past, Crohn’s disease (CD) has been understood primarily as an immunologic disorder characterized by an abnormal T-cell response. Recent in vitro and in vivo data suggests that CD may instead be precipitated by innate immune dysfunction resulting from a combination of genetic and environmental factors. Some reports have demonstrated a defective immune response in a variety of other cellular components, including neutrophils, monocytes and dendritic cells. Recent studies of granulocyte-macrophage colony-stimulating factor (GM-CSF) in CD, aiming to stimulate the innate immune system with the conception that an innate immune defect underlies the development of the disease, have been demonstrated a clinical benefit and reinforce this evolving understanding of the disease.

Impaired neutrophil chemotaxis in Crohn's disease relates to reduced production of chemokines and can be augmented by granulocyte-colony stimulating factor

BACKGROUND

Defective neutrophil recruitment has been described as a primary pathogenic abnormality in Crohn's disease. Cantharidin-induced blisters provide a novel investigative tool to assess cellular influx and inflammatory mediator production during acute inflammation and allows the effects of therapy on these parameters to be measured.

AIMS

To determine whether reduced neutrophil tissue penetration in Crohn's disease relates to impaired production of inflammatory mediators, and whether it can be reversed by granulocyte-colony stimulating factor (G-CSF).

METHODS

Neutrophil and monocyte/macrophage populations and inflammatory mediators were measured in cantharidin blisters at 24 h. Neutrophil chemotaxis was assessed in vitro using blister fluid as the chemoattractant. The effect of s.c. G-CSF on blister phenotype was determined.

RESULTS

Significantly fewer neutrophils migrated into blisters in Crohn's patients. The production of neutrophil chemokines, but not other inflammatory mediators, was reduced. This significantly correlated with reduced chemotaxis in vitro. Differences were unrelated to caspase-recruitment domain 15 genotype. G-CSF significantly increased blister neutrophil concentrations in control subjects and Crohn's patients.

CONCLUSIONS

Reduced neutrophil migration during acute inflammation in Crohn's disease is associated with impaired production of appropriate chemoattractants. G-CSF therapy increases neutrophil tissue migration, which may partially account for its observed therapeutic effect.

Can unresolved infection precipitate autoimmune disease?

Autoimmune diseases are frequently postulated to arise as post-infectious phenomena. Here we survey the evidence supporting these theories, with particular emphasis on Crohn's disease and ankylosing spondylitis. Direct proof that infection establishes persistent autoimmunity remains lacking, although it may provoke a prolonged inflammatory response when occurring on a susceptible immunological background. The argument of infective causality is by no means trivial, since it carries important consequences for the safety of vaccine development.

Long-term outcome of intractable ulcerating enterocolitis of infancy

BACKGROUND

Chronic enterocolitis is rare in infancy and accounts for less than 0.5% of all newly diagnosed inflammatory bowel disease (IBD) in the UK. Presentation at this young age is usually indicative of underlying immunodeficiency/immunodysregulation. A group of such infants suffer intractable ulcerating enterocolitis of infancy (IE) in which there is a pan-enteritis with marked oro-anal involvement and deep flask like mucosal ulcers throughout the colon.

METHODS

Retrospective review of presenting features, treatment and long-term outcome in a series of 8 children with typical IE.

RESULTS

The 8 children were aged between 1 and 4 weeks at onset (median 2 weeks, mean 2.3 weeks), of which 7 were followed up for 2-22 years (median 7.5 years, mean 11 years). All 8 children had an intractable disease course requiring a colectomy for control of symptoms. The median age at colectomy was 1.7 years (range 4 months-4 years). Three children developed a generalised lymphadenopathy due to uncontrolled EBV-related lymphoid proliferations (ages 4, 12, 18). These comprised a monomorphous B-lymphoycte lympho-proliferative disorder, a large pleomorphic follicular lymphoma, and a high grade pleomorphic B cell non-Hodgkin's lymphoma.

CONCLUSIONS

Infants with IE have a high risk of developing lymphomatous proliferations that appears to be related to the underlying immunodysregulation. Use of aggressive immunosuppression and acquisition of EBV infection appears to accelerate this process; hence we advocate early colectomy in confirmed cases. In children with IE screening for EBV and vigilance for abnormal lymphoid proliferations is paramount.

An open-labelled study of granulocyte colony-stimulating factor in the treatment of active Crohn's disease

BACKGROUND

Immunodeficiency syndromes associated with a Crohn's-like illness suggest innate immune defects may lead to Crohn's disease. Anecdotal cases using haemopoietic colony-stimulating factors report improvement in intestinal disease associated with these syndromes.

AIM

To test the safety and efficacy of recombinant human granulocyte colony-stimulating factor in active Crohn's disease.

METHODS

In an open-labelled 12-week trial, patients with a Crohn's Disease Activity Index between 220 and 450 were treated with recombinant human granulocyte colony-stimulating factor (filgrastim, Neupogen). Concomitant immunosuppressants were prohibited except prednisone < or =20 mg/day. Patient's received recombinant human granulocyte colony-stimulating factor 300 mcg daily subcutaneously adjusted to achieve an absolute neutrophil count between 25 and 35 x 10(9)/L.

RESULTS

Twenty patients were enrolled with a mean initial Crohn's Disease Activity Index of 307 (range: 234-428). Fifteen patients (75%) completed 8 weeks; 13 patients (65%) completed 12 weeks with the mean Crohn's Disease Activity Index for patients continuing through those times of 196 (range: 36-343) and 162 (range: 20-308), respectively. At week 12, 11 patients (55%) demonstrated a decrease of at least 70 points; five (25%) achieved a sustained remission. The mean decrease was statistically significant at each assessment time-point. Three of four patients with fistulae had a positive response. Adverse effects included bone pain, mostly mild resolving with continued treatment. One patient was hospitalized with a viral-like syndrome but it is uncertain if this was treatment related.

CONCLUSION

Recombinant human granulocyte colony-stimulating factor is safe and potentially effective therapy for active Crohn's disease.

Infections in patients with inherited defects in phagocytic function

Patients with defects in phagocytic function are predisposed to intracellular microorganisms and typically have early dissemination of the infection. Recognition of the underlying disorder and aggressive antimicrobial therapy has been beneficial for the patients. Improved understanding of the pathophysiology has also affected patient management by allowing specific, targeted immunomodulatory intervention. The disorders described in this review are not common but have had a significant impact on our understanding of the role of phagocytic cells in host defense. Conversely, understanding the role of the neutrophil and macrophage in infection has benefited not just the patients described in this review but also other patients with similar disease processes.

Crohn's disease: an immunodeficiency?

Autoimmunity appears to be a key factor in Crohn's disease as it develops in a genetically susceptible host if the immunological tolerance towards bacterial antigens within the gastrointestinal tract is abrogated. The resulting excessive immunological activity leads to a chronic sometimes transmural inflammatory process within the bowel wall. However, several lines of evidence are compatible with an immunodeficiency preceding these processes: humoral or cellular immune defects can predispose to inflammatory bowel disease. An increased bacterial adherence at the intestinal mucosa, which is possibly attributable to impaired expression of defensins was observed in Crohn's disease. Furthermore, the 3020insC mutation of the NOD2/CARD15 gene which is associated with Crohn's disease results in impaired cytokine transcription. Lastly, therapeutic approaches such as the use of antibiotic therapy or granulocyte macrophage colony stimulating factor are in line with the concept of an immunodeficiency being a crucial element in Crohn's disease.

Alteration in expression of beta 2 integrins on lamina propria lymphocytes in ulcerative colitis and Crohn's disease

We have previously demonstrated by immunohistochemistry that mucosal expression of beta 2 integrins was enhanced in Crohn's disease and ulcerative colitis as compared to normal controls. We aimed, therefore, to determine whether there was a corresponding alteration in the expression of CD11a/CD18 (LFA-1), the primary lymphocyte beta 2 integrin, among the principal subsets of lamina propria lymphocytes (LPLs). Accordingly, LPLs were extracted from surgical resection specimens derived from patients with Crohn's colitis, ulcerative colitis, and from noninflamed controls. Following immunofluorescent staining, three-color flow-cytometry analysis identified LPLs on the basis of CD45 side scatter gating, which in turn, were further subdivided into CD4(+), CD8(+), and CD19(+) cells to account for the predominant T and B cells in the lamina propria. Expression patterns of CD11a, the alpha-subunit of LFA-1; CD18, the beta-subunit of LFA-1; and alpha d, a novel alpha-subunit of the beta 2 integrin family were assessed for each of these lymphocyte subsets. In Crohn's disease and ulcerative colitis there was an increased mean percentage expression of CD4(+) cells and CD11a(+) cells compared with noninflamed controls. CD11a was more likely to be expressed on CD4(+) cells in both Crohn's disease and ulcerative colitis and compared with controls and less expressed on CD19(+) cells. It is likely that an influx of CD4(+)11a(+) cells into the lamina propria accounted for these changes. These results suggest that although currently there is great interest in harnessing alpha 4 beta 7 in treatment of inflammatory bowel disease, further consideration should be given to the role of CD11a in these disease states.

Neutrophil migration into indomethacin induced rat small intestinal injury is CD11a/CD18 and CD11b/CD18 co-dependent

BACKGROUND

Neutrophils may exacerbate intestinal inflammatory diseases through secretion of proteolytic enzymes and reactive oxygen and nitrogen intermediates.

AIMS

To define the mechanisms involved in neutrophil infiltration into the non-steroidal anti-inflammatory disease inflamed intestine to develop strategies to regulate this process.

METHODS

The small intestinal epithelium of (15 mg/kg) indomethacin treated rats was examined for cytokine mRNA. The kinetics of neutrophil accumulation into the gastrointestinal tract (including lumen contents) of inflamed rats was determined using radiolabelled (111In) neutrophils injected intravenously followed by a three hour migration period. To determine which adhesion molecules were critical for migration, rats were also injected with function blocking monoclonal antibodies to the beta2 (CD11/CD18) integrins.

RESULTS

Interleukin 1beta, interleukin 1 receptor II, tumour necrosis factor alpha, and monocyte inflammatory peptide 2 but not monocyte chemoattractant protein 1 mRNA were detected in the epithelium within hours of indomethacin injection. Neutrophils were detectable in the small intestine and intestinal lumen by six hours and continued to accumulate until 48 hours post indomethacin injection. Neutrophil accumulation in the intestine was essentially blocked by anti-CD18, and partially blocked by either anti-CD11a or CD11b antibody treatment. Migration into the intestinal lumen was reduced by anti-CD11b.

CONCLUSIONS

The small intestinal epithelium acts as one source of cytokines with properties important in the recruitment of neutrophils. In turn, neutrophil migration into the indomethacin inflamed small intestine is mediated by CD11a/CD18 and CD11b/CD18.

Immunological basis of inflammatory bowel disease: role of the microcirculation

Inflammatory bowel disease (IBD) is a chronic inflammatory condition of the intestine and/or colon of unknown etiology in which patients suffer from severe diarrhea, rectal bleeding, abdominal pain, fever, and weight loss. Active episodes of IBD are characterized by vasodilation, venocongestion, edema, infiltration of large numbers of inflammatory cells, and erosions and ulcerations of the bowel. It is becoming increasingly apparent that chronic gut inflammation may result from a dysregulated immune response toward components of the normal intestinal flora, resulting in a sustained overproduction of proinflammatory cytokines and mediators. Many of these Th1 and macrophage-derived cytokines and lipid metabolites are known to activate microvascular endothelial cells, thereby promoting leukocyte recruitment into the intestinal interstitium. This review discusses the basic immune mechanisms involved in the regulation of inflammatory responses in the gut and describes how a breakdown in this protective response initiates chronic gut inflammation.