Leukocyte Adhesion Deficiency Type Research Articles

Eight induced pluripotent stem cell lines (iPSCs) derived from two patients with Leukocyte adhesion deficiency Type I (LAD I) with mutations in the ITGB2 gene

Leukocyte Adhesion Deficiency Type I (LAD I) is a rare inborn error of immunity caused by mutations in the ITGB2 gene coding for β2-integrin CD18 on the surface of leukocytes. Affected patients display severe clinical manifestations with life threatening infections and inflammatory complications due to an impaired ability of leukocytes to transmigrate from the blood vessel to the tissue. Here we describe the generation of eight induced pluripotent stem cell lines from two patients with LAD I and mutations in the ITGB2 gene. With this project we contribute patient individualized cell lines for explorative research in a rare disease

Sequence variants underlying severe combined immunodeficiency and leukocyte adhesion deficiency type 1 in six consanguineous families.

Inborn errors of immunity (IEI) are defined as genetic disorders affecting the immune system and resulting in diverse clinical signs and symptoms. Despite the lack of diagnosis and unavailability of IEI estimation in the Pakistani population, consanguinity is exacerbating its prevalence. The current study focuses on severe combined immunodeficiency (SCID) and leukocyte adhesion deficiency type 1 (LAD1). SCID is associated with the life-threatening symptoms developing at post-birth. LAD1 is clinically characterized by recurrent bacterial infections related to the skin, mouth, and respiratory tract owing to impaired leukocytes. Herein, in six consanguineous families, flow cytometry was used to evaluate the patient's immune status. Whole-exome sequencing (WES) was then conducted to search for the causative variations in immunodeficiency genes. Sanger sequencing was used to assess the segregation of the variants with the disorder within the families. Sequence analysis revealed five homozygous variants in four different causative genes. This included four novel nonsense variants in CD70 p.(Thr126Profs*33), CD3e p.(Trp151*), IL7R p.(Val138Ilefs*10), and ITGB2 p.(Ser627Valfs*61), and one previously reported in ITGB2 p.(Cys62*). In one of the families, two variants in two different genes, including DNAH6 p.(Tyr2653His) and NIPAL4 p.(Gly121Ser), were detected in an unclassified patient. All the identified variants were found in a homozygous state in the patient but in a heterozygous state in the available parents. The study will facilitate the diagnosis and management of IEI patients.

The sufficiency of genetic diagnosis in managing patients with inborn errors of immunity during prenatal care and childbearing.

Individuals with inborn errors of immunity face challenges in fertility, pregnancy, and genetic disorder transmission. Prenatal genetic counseling is crucial, especially in tribal societies with consanguineous unions. Ten families with confirmed inborn errors of immunity were studied, revealing diverse pregnancy decisions: An architect with autosomal dominant STAT-1 gain of function underwent prenatal diagnosis despite initial plans for preimplantation genetic diagnosis. In a consanguineous family, two children died from leukocyte adhesion deficiency type 1 because the father refused prenatal diagnosis. First cousins opted against terminating the second pregnancy, resulting in two children affected by Bruton disease. Another consanguineous couple, with two children afflicted by ataxia-telangiectasia, chose oocyte donation for their third child, ensuring a healthy birth. Recurrent pregnancy loss was observed in a mother subsequently diagnosed with ZAP70 deficiency. A mother with Wiskott-Aldrich syndrome child opted for in vitro fertilization, leading to a healthy birth post-prenatal diagnosis. A misdiagnosis of anaplastic anemia occurred in a family with multiple instances of Wiskott-Aldrich syndrome. A leukocyte adhesion deficiency type 1 case led to parental dissolution due to the father's refusal to acknowledge the condition. In a non-consanguineous couple, the father's diagnosis of TACI deficiency influenced the mother's decision to discontinue pregnancy post-prenatal diagnosis. Genetic diagnosis alone cannot optimize prenatal care for immune dysregulation disorders. Various factors, including patient education, societal norms, ethics, and economics, impact pregnancy decisions. Clinical immunologists must integrate these elements into guidance strategies to enhance patient outcomes.

Leukocyte adhesion deficiency type 1 with normal expression of CD 11a, CD11b and CD11c

Leukocyte adhesion deficiency type 1 with normal expression of CD 11a, CD11b and CD11c

Mutations in the SLC35C1 gene, contributing to significant differences in fucosylation patterns, may underlie the diverse phenotypic manifestations observed in leukocyte adhesion deficiency type II patients

Congenital disorders of glycosylation (CDG) are a large family of genetic diseases resulting from defects in the synthesis of glycans and the attachment of glycans to macromolecules. The CDG known as leukocyte adhesion deficiency II (LAD II) is an autosomal, recessive disorder caused by mutations in the SLC35C1 gene, encoding a transmembrane protein of the Golgi apparatus, involved in GDP-fucose transport from the cytosol to the Golgi lumen. In this study, a cell-based model was used as a tool to characterize the molecular background of a therapy based on a fucose-supplemented diet. Such therapies have been successfully introduced in some (but not all) known cases of LAD II. In this study, the effect of external fucose was analyzed in SLC35C1 KO cell lines, expressing 11 mutated SLC35C1 proteins, previously discovered in patients with an LAD II diagnosis. For many of them, the cis-Golgi subcellular localization was affected; however, some proteins were localized properly. Additionally, although mutated SLC35C1 caused different α-1–6 core fucosylation of N-glycans, which explains previously described, more or less severe disorder symptoms, the differences practically disappeared after external fucose supplementation, with fucosylation restored to the level observed in healthy cells. This indicates that additional fucose in the diet should improve the condition of all patients. Thus, for patients diagnosed with LAD II we advocate careful analysis of particular mutations using the SLC35C1-KO cell line-based model, to predict changes in localization and fucosylation rate. We also recommend searching for additional mutations in the human genome of LAD II patients, when fucose supplementation does not influence patients’ state.

Analysis of Clinical, Immunological and Molecular Features of Leukocyte Adhesion Deficiency Type I in Egyptian Children

PurposeLeukocyte adhesion deficiency (LAD) represents a rare group of inherited inborn errors of immunity (IEI) characterized by bacterial infections, delayed umbilical stump separation, and autoimmunity. This single-center study aimed at describing the clinical, immunological, and molecular characterizations of 34 LAD-I Egyptian pediatric patients.MethodsDetails of 34 patients’ personal medical history, clinical and laboratory findings were recorded; Genetic material from 28 patients was studied. Mutational analysis was done by Sanger sequencing.ResultsOmphalitis, skin and soft tissue infections with poorly healing ulcers, delayed falling of the umbilical stump, and recurrent or un-resolving pneumonia were the most common presentations, followed by chronic otitis media, enteropathy, periodontitis; and recurrent oral thrush. Persistent leukocytosis and neutrophilia were reported in all patients, as well as CD18 and CD11b deficiency. CD18 expression was < 2% in around 90% of patients. Sixteen different pathological gene variants were detected in 28 patients who underwent ITGß2 gene sequencing, of those, ten were novel and six were previously reported. Three families received a prenatal diagnosis. Patients were on antimicrobials according to culture’s results whenever available, and on prophylactic Trimethoprim-Sulfamethoxazole 5 mg/kg once daily, with regular clinical follow up. Hematopoietic stem cell transplantation (HSCT) was offered for 4 patients. However due to severity of the disease and delay in diagnosis, 58% of the patients passed away in the first 2 years of life.ConclusionThis study highlights the importance of early diagnosis and distribution of ITGß2 gene mutation in Egyptian children. Further molecular studies, however, remain a challenging necessity for better disease characterization in the region.

INTEGRIN BETA2 GENE VARIANT CAUSING LEUKOCYTE ADHESION DEFICIENCY TYPE 1 IN A PAKISTANI FAMILY

Background: Leukocyte adhesion deficiency type 1 (LAD1), an autosomal recessive condition, arises from partial or complete deficiency of CD18 expression. LAD1 patients commonly manifest recurrent skin and respiratory tract infections, delayed umbilical cord separation, and impaired wound healing due to hindered leukocyte migration. This study aims to clinically and molecularly diagnose LAD in a highly consanguineous Pakistani family, investigating a recurrent mutation within the integrin ?2 (ITGB2) gene. Methods: A comprehensive clinical and molecular diagnosis of LAD1 was made in on a patient from a consanguineous Pakistani family. Lymphocyte subset analysis was performed using a flow cytometer, followed by whole exome sequencing and DNA Sanger sequencing to identify the pathogenic mutation within the ITGB2 gene. Further to provide genetic counselling all the healthy siblings were also Sanger sequenced. Results: Flow cytometry indicated CD18 deficiency, while sequencing of the ITGB2 gene unveiled a nonsense mutation, c.186C&gt;A, p. (Cys62*), located in exon four. This mutation segregates in an autosomal recessive pattern within the family. Conclusion: A mutation c.186C&gt;A (Cys62*) in a patient of LAD1 was identified which is potentially pathogenic in nature. Pak J Physiol 2024;20(1):15-8

Clinical manifestations and expression of CD18 to guide the diagnosis of leukocyte adhesion deficiency type 1: Mexico experience

Background: Leukocyte adhesion deficiency type 1 (LAD-1) is an inborn error of immunity characterized by a defect in leukocyte trafficking. Methods: Patients with clinical suspicion of LAD-1 were referred to our institution. Complete blood count and flow cytometric analysis, to identify the expression of CD18, CD11b, and the lymphocyte population phenotyping, were performed, and statistical analysis was completed. Results: We report clinical manifestations and immunological findings of six Mexican patients diagnosed with LAD-1. The diagnosis was based on typical clinical presentation, combined with laboratory demonstration of leukocytosis, and significant reduction or near absence of CD18 and its associated molecules CD11a, CD11b, and CD11c on leukocytes. We found atypical manifestations, not described in other countries, such as early-onset autoimmunity or infections caused by certain microorganisms. Conclusions: Patients with LAD-1 may present with atypical manifestations, making flow cytometry an indispensable tool to confirm the diagnosis. We present the first report of LAD-1 patients in a Latin American country.

Clinical manifestations and expression of CD18 to guide the diagnosis of leukocyte adhesion deficiency type 1: Mexico experience.

Leukocyte adhesion deficiency type 1 (LAD-1) is an inborn error of immunity characterized by a defect in leukocyte trafficking. Patients with clinical suspicion of LAD-1 were referred to our institution. Complete blood count and flow cytometric analysis, to identify the expression of CD18, CD11b, and the lymphocyte population phenotyping, were performed, and statistical analysis was completed. We report clinical manifestations and immunological findings of six Mexican patients diagnosed with LAD-1. The diagnosis was based on typical clinical presentation, combined with laboratory demonstration of leukocytosis, and significant reduction or near absence of CD18 and its associated molecules CD11a, CD11b, and CD11c on leukocytes. We found atypical manifestations, not described in other countries, such as early-onset autoimmunity or infections caused by certain microorganisms. Patients with LAD-1 may present with atypical manifestations, making flow cytometry an indispensable tool to confirm the diagnosis. We present the first report of LAD-1 patients in a Latin American country.

Clinical manifestations and expression of CD18 to guide the diagnosis of leukocyte adhesion deficiency type 1: Mexico experience

Background: Leukocyte adhesion deficiency type 1 (LAD-1) is an inborn error of immunity characterized by a defect in leukocyte trafficking. Methods: Patients with clinical suspicion of LAD-1 were referred to our institution. Complete blood count and flow cytometric analysis, to identify the expression of CD18, CD11b, and the lymphocyte population phenotyping, were performed, and statistical analysis was completed. Results: We report clinical manifestations and immunological findings of six Mexican patients diagnosed with LAD-1. The diagnosis was based on typical clinical presentation, combined with laboratory demonstration of leukocytosis, and significant reduction or near absence of CD18 and its associated molecules CD11a, CD11b, and CD11c on leukocytes. We found atypical manifestations, not described in other countries, such as early-onset autoimmunity or infections caused by certain microorganisms. Conclusions: Patients with LAD-1 may present with atypical manifestations, making flow cytometry an indispensable tool to confirm the diagnosis. We present the first report of LAD-1 patients in a Latin American country.

A novel leukocyte adhesion deficiency type III mutation manifests functional importance of the compact FERM domain in kindlin-3

BackgroundLeukocyte adhesion deficiency III (LAD-III) is a rare autosomal recessive syndrome characterized by functional deficiencies of platelets and leukocytes that occurs due to mutations in the FERMT3 gene encoding kindlin-3. Kindlin-3 is a FERM domain–containing adaptor protein that is essential in integrin activation. We have previously demonstrated that the FERM domain of kindlin-3 is structurally compact and plays an important role in supporting integrin activation in a mouse model. The impact of destabilizing the compact FERM domain in kindlin-3 on the development of LAD-III in humans remains uncertain. ObjectivesTo use primary cells from a patient with LAD-III to validate the role of the compact FERM domain in kindlin-3 function in platelets and leukocytes. MethodsThe patient is a 4-year-old girl who since infancy has displayed clinical features of LAD-III. Patient platelets and leukocytes were functionally analyzed, and structural analysis of the kindlin-3 variant was conducted. ResultsWe identified a novel homozygous missense mutation in the FERMT3 (c.412G>A, p.E138K) FERM domain. Substantially reduced levels of kindlin-3 were detected in the proband’s platelets and leukocytes. Functional evaluation verified that integrin αIIbβ3-mediated platelet activation, spreading, and aggregation and β2-integrin–mediated neutrophil adhesion and spreading were significantly compromised. Structural analysis revealed that this newly identified E138K substitution in kindlin-3 destabilizes the compacted FERM domain, resulting in poor expression of kindlin-3 in blood cells and subsequent LAD-III. ConclusionWe have identified a novel missense mutation and verified the functional significance of the compact kindlin-3 FERM domain in supporting integrin functions in platelets and leukocytes.

Rare and heterogeneous manifestations of leucocyte adhesion deficiency type 1: report of two cases with diagnostic dilemmas and novel ITGB2 mutation

BackgroundPrimary immunodeficiency disorders (PID) are rare disorders with heterogeneous manifestations, overlapping with other diseases such as autoimmunity, malignancy, and infections. This makes the diagnosis very challenging and delays management. Leucocyte adhesion defects (LAD) are a group of PIDs in which patients lack adhesion molecules on leukocytes needed for their emigration through blood vessels to the site of infection. Patients with LAD can present with diverse clinical features including severe and life-threatening infections, early in life, and the absence of pus formation around infection or inflammation. There is often delayed umbilical cord separation, omphalitis, late wound healing, and a high white blood cell count. If not recognized and managed early, can lead to life-threatening complications and death.Case PresentationLAD 1 is characterized by homozygous pathogenic variants in the integrin subunit beta 2 (ITGB2) gene. We report two cases of LAD1 with unusual presentations (post-circumcision excessive bleeding and chronic inflammation of the right eye) which were confirmed by flow cytometric analysis and genetic testing. We found two disease-causing ITGB2 pathogenic variants in both cases.ConclusionsThese cases highlight the importance of a multidisciplinary approach to recognizing clues in patients with uncommon manifestations of a rare disease. This approach initiates a proper diagnostic workup of primary immunodeficiency disorder leading to a better understanding of the disease, and appropriate patient counseling, and helps clinicians to be better equipped to deal with complications.

Clinical and Osteopetrosis-Like Radiological Findings in Patients with Leukocyte Adhesion Deficiency Type III.

Leukocyte and platelet integrin function defects are present in leukocyte adhesion deficiency type III (LAD-III) due to mutations in FERMT3. Additionally, osteoclast/osteoblast dysfunction develops in LAD-III. To discuss the distinguishing clinical, radiological, and laboratory features of LAD-III. This study included the clinical, radiological, and laboratory characteristics of twelve LAD-III patients. The male/female ratio was 8/4. The parental consanguinity ratio was 100%. Half of the patients had a family history of patients with similar findings. The median age at presentation and diagnosis was 18 (1-60) days and 6 (1-20) months, respectively. The median leukocyte count on admission was 43,150 (30,900-75,700)/μL. The absolute eosinophil count was tested in 8/12 patients, and eosinophilia was found in 6/8 (75%). All patients had a history of sepsis. Other severe infections were pneumonia (66.6%), omphalitis (25%), osteomyelitis (16.6%), gingivitis/periodontitis (16%), chorioretinitis (8.3%), otitis media (8.3%), diarrhea (8.3%), and palpebral conjunctiva infection (8.3%). Four patients (33.3%) received hematopoietic stem cell transplantation (HSCT) from HLA-matched-related donors, and one deceased after HSCT. At initial presentation, 4 (33.3%) patients were diagnosed with other hematologic disorders, three patients (P5, P7, and P8) with juvenile myelomonocytic leukemia (JMML), and one (P2) with myelodysplastic syndrome (MDS). In LAD-III, leukocytosis, eosinophilia, and bone marrow findings may mimic pathologies such as JMML and MDS. In addition to non-purulent infection susceptibility, patients with LAD-III exhibit Glanzmann-type bleeding disorder. In LAD-III, absent integrin activation due to kindlin-3 deficiency disrupts osteoclast actin cytoskeleton organization. This results in defective bone resorption and osteopetrosis-like radiological changes. These are distinctive features compared to other LAD types.

The Role of LFA-1 for the Differentiation and Function of Regulatory T Cells-Lessons Learned from Different Transgenic Mouse Models.

Regulatory T cells (Treg) are essential for the maintenance of peripheral tolerance. Treg dysfunction results in diverse inflammatory and autoimmune diseases with life-threatening consequences. β2-integrins (CD11a-d/CD18) play important roles in the migration of leukocytes into inflamed tissues and cell signaling. Of all β2-integrins, T cells, including Treg, only express CD11a/CD18, termed lymphocyte function-associated antigen 1 (LFA-1), on their surface. In humans, loss-of-function mutations in the common subunit CD18 result in leukocyte adhesion deficiency type-1 (LAD-1). Clinical symptoms vary depending on the extent of residual β2-integrin function, and patients may experience leukocytosis and recurrent infections. Some patients can develop autoimmune diseases, but the immune processes underlying the paradoxical situation of immune deficiency and autoimmunity have been scarcely investigated. To understand this complex phenotype, different transgenic mouse strains with a constitutive knockout of β2-integrins have been established. However, since a constitutive knockout affects all leukocytes and may limit the validity of studies focusing on their cell type-specific role, we established a Treg-specific CD18-floxed mouse strain. This mini-review aims to delineate the role of LFA-1 for the induction, maintenance, and regulatory function of Treg in vitro and in vivo as deduced from observations using the various β2-integrin-deficient mouse models.

A fatal yet salvageable inborn error – leukocyte adhesion deficiency

Leukocyte adhesion deficiency (LAD) Type 1 is a rare inborn error in infants characterized by delayed umbilical cord detachment, non-healing ulcers, and leukocytosis. Initially, knowledge of LAD was limited to the impairment of granulocyte function due to the scarcity of cases. However, as more and more cases are being reported, the knowledge of the bio-physiology of white blood cells, platelets, and various intercellular reactivity and signaling provides a new perception of this disease. We present a 17-day-old female child who presented with complaints of fever and redness in the perianal region and popliteal fossa. Investigations showed leukocytosis in blood and cerebrospinal fluid (CSF), raised C-Reactive Protein (CRP), and Pseudomonas-positive blood and CSF culture. Flow cytometry revealed the absence of CD18, CD11a, and CD11c. Aggressive antimicrobial agents were started; however, the baby died on day 30 of life. In this report, we emphasize the essential investigations needed for early diagnosis and effective precautions through which we can decrease the fatality rate of this rare disorder.

Periodontal Management of Leukocyte Adhesion Deficiency Type-I with Photodynamic Therapy-A Case Report

Leukocyte Adhesion Deficiency type I (LAD-I) is a rare autosomal recessive disorder affecting the immune system which is characterised by defects in white blood cell integrin receptors leading to impaired adhesion and chemotaxis with increased susceptibility to recurrent infections, delayed wound healing, and periodontitis. A case of aggressive form of generalised periodontitis in a 19- year-old girl with LAD-I is presented in this case report. The medical diagnosis was made on the basis of characteristic clinical and laboratory findings suggestive of LAD, particularly the total absence of Cluster of Differentiation (CD)18, CD11a, CD11b, and CD11c which were determined by flow cytometry. After non surgical periodontal therapy, photodynamic therapy with Low Level Laser Therapy (LLT) was performed. After 3 months, reduced inflammatory signs and improved periodontal health was observed. This report highlights the importance of the differential diagnosis of severe immunodeficiency disorders. It also emphasises the joint role of medical and dental specialists to control oral infections and thereby preventing tooth loss.

Impaired Treg-DC interactions contribute to autoimmunity in leukocyte adhesion deficiency type 1.

Leukocyte adhesion deficiency type 1 (LAD-1) is a rare disease resulting from mutations in the gene encoding for the common β-chain of the β2-integrin family (CD18). The most prominent clinical symptoms are profound leukocytosis and high susceptibility to infections. Patients with LAD-1 are prone to develop autoimmune diseases, but the molecular and cellular mechanisms that result in coexisting immunodeficiency and autoimmunity are still unresolved. CD4+FOXP3+ Treg are known for their essential role in preventing autoimmunity. To understand the role of Treg in LAD-1 development and manifestation of autoimmunity, we generated mice specifically lacking CD18 on Treg (CD18Foxp3), resulting in defective LFA-1 expression. Here, we demonstrate a crucial role of LFA-1 on Treg to maintain immune homeostasis by modifying T cell-DC interactions and CD4+ T cell activation. Treg-specific CD18 deletion did not impair Treg migration into extralymphatic organs, but it resulted in shorter interactions of Treg with DC. In vivo, CD18Foxp3 mice developed spontaneous hyperplasia in lymphatic organs and diffuse inflammation of the skin and in multiple internal organs. Thus, LFA-1 on Treg is required for the maintenance of immune homeostasis.

Preclinical Evaluation of Foamy Virus Vector-Mediated Gene Addition in Human Hematopoietic Stem/Progenitor Cells for Correction of Leukocyte Adhesion Deficiency Type 1.

Ex vivo gene therapy procedures targeting hematopoietic stem and progenitor cells (HSPCs) predominantly utilize lentivirus-based vectors for gene transfer. We provide the first pre-clinical evidence of the therapeutic utility of a foamy virus vector (FVV) for the genetic correction of human leukocyte adhesion deficiency type 1 (LAD-1), an inherited primary immunodeficiency resulting from mutation of the β2 integrin common chain, CD18. CD34+ HSPCs isolated from a severely affected LAD-1 patient were transduced under a current good manufacturing practice-compatible protocol with FVV harboring a therapeutic CD18 transgene. LAD-1-associated cellular chemotactic defects were ameliorated in transgene-positive, myeloid-differentiated LAD-1 cells assayed in response to a strong neutrophil chemoattractant in vitro. Xenotransplantation of vector-transduced LAD-1 HSPCs in immunodeficient (NSG) mice resulted in long-term (∼5 months) human cell engraftment within murine bone marrow. Moreover, engrafted LAD-1 myeloid cells displayed in vivo levels of transgene marking previously reported to ameliorate the LAD-1 phenotype in a large animal model of the disease. Vector insertion site analysis revealed a favorable vector integration profile with no overt evidence of genotoxicity. These results coupled with the unique biological features of wild-type foamy virus support the development of FVVs for ex vivo gene therapy of LAD-1.

GENETICALLY CONFIRMED TYPE I LEUKOCYTE ADHESION DEFICIENCY IN A TWO-YEAR-OLD MALE

<h3>Introduction</h3> Leukocyte adhesion deficiency (LAD) type 1 affects about one in a million people world-wide. Presentation typically includes delayed separation of the umbilical cord, neutrophilia, and repeated bacterial infections soon after birth. Here we present a case of a 2-year-old male who presented in respiratory failure later found to have genetically confirmed type 1 LAD. <h3>Case Description</h3> A 2-year-old male in state custody presented to an outside hospital with fever and respiratory distress secondary to croup. Hospital course was complicated by right vocal cord avulsion likely secondary to trauma, difficulty in extubation requiring steroids and tracheostomy, persistent leukocytosis with neutrophilia, and reccuring fevers. He was transferred to our hospital after CD18/CDb11 expression was found to be 0%. We sent primary immunodeficiency genetic testing confirming a pathogenic variant in ITGB2 and 22q22.3 pathogenic deletion which included ITGB2, AIRE and ICOSLG. <h3>Discussion</h3> When given an unclassical and convoluted history, relying on more objective data like laboratory results and physical exam is crucial. Our case was challenging due to a complex social situation making obtaining a good history difficult and inability to examine the patient on initial consultation. History revealed insignificant infection history and no delayed separation of the umbilical cord. Therefore, before being able to examine the patient and obtain genetic testing there was some skepticism of the diagnosis despite supporting flow cytometry. Once the patient arrived at our facility, physical exam revealed wound healing characteristic of LAD, increasing suspicion of the disease. Genetic testing confirmed LAD, as he was hemizygous for a pathogenic variant in ITGB2.

Sequence variants in the ITGB2 gene underlying leukocyte adhesion deficiency Type-1 in four consanguineous families

Integrins are integral transmembrane proteins involved in various biological activities. One such protein β2 integrin CD18, encoded by ITGB2 gene, is involved in leukocyte adhesion and wound healing. Leukocyte adhesion and crawling being the key process in combating infections are mainly facilitated by β2 integrins. Sequence variants in the ITGB2 gene cause leukocyte adhesion deficiency, type I (LAD1). To search for the disease-causing sequence variants in four patients with LAD1 born to four different consanguineous parents of Pakistani origin. Flow cytometry was used to measure CD18 levels. Genomic DNA was extracted from the blood of the patients, parents, and healthy siblings. Using exon-specific primers, the ITGB2 gene was Sanger sequenced. Clinical features including skin abscesses, delayed umbilical cord separation, mild omphalitis, and neutrophilia were recorded in the patients. Flow-cytometric analysis revealed highly reduced CD18 levels (< 2 %) in the patients. Sequence analysis of the ITGB2 gene revealed four disease-causing variants, including two novels [p.(Tyr130*), p.(Ala245Pro)], and two previously reported [p. (Cys62*), p.(Asp128Tyr)]. Identification of the LAD1 causative variants further expanded the mutation spectrum in the ITGB2 gene. This study will facilitate genetic counseling of the families carrying LAD1 type features in the Pakistani population.