Leukocyte Adhesion Deficiency – Causes, Symptoms, Treatment

Leukocyte adhesion deficiency (LAD) is an immunodeficiency cellular molecules adhesion deficiency type-1 (LAD-I) is a rare, inherited combined deficiency disorder involving both B and T cells and is characterized by an inability of leukocytes to migrate to the site of infection to kill offending microbes. It is a combined (B cell) and cellular (T cell) immunodeficiency disorder. This activity describes the evaluation and management of leukocyte adhesion deficiency and reviews the role of the interprofessional team in improving care for patients with this condition.

Leukocyte adhesion deficiency type 1 is a disorder that causes the immune system to malfunction, resulting in a form of immunodeficiency. Immunodeficiencies are conditions in which the immune system is not able to protect the body effectively from foreign invaders such as viruses, bacteria, and fungi. Starting from birth, people with leukocyte adhesion deficiency type 1 develop serious bacterial and fungal infections.

Major immunologic features[]rx[rx]:

• There is an inability to form pus.
• There is a deficiency of various glycoproteins including LFA-1/Mac-1, glycoprotein 150/95.
• Leukocytes cannot migrate to infection sites to kill invading microorganisms due to mutations in the CD18 glycoprotein.
• Adhesion molecules deficiency results in an abnormal inflammatory response and eventually recurrent bacterial infections.

Causes of Leukocyte Adhesion Deficiency

Primarily, leukocytes cannot escape from the blood to tissues that have been attacked by microbes. Continuous surveillance of foreign antigens by leukocyte trafficking suffers disruption as well. There are three different types of LAD[rx][rx]:

• Type I – in which steady adhesion of leukocyte to endothelial surfaces is defective by mutations in CD18 gene resulting in defective or deficient beta-2 integrin
• Type II – in which there is an absence of Sialyl Lewis X of E-selectin
• Type III – in which there is a defect in beta integrins 1, 2, and 3; this impairs the integrin activation cascade – specifically, a mutation in the kindlin-3 gene causes this type of LAD

LAD has an autosomal recessive mode of inheritance.

• Seven new mutations in the ITGB2 gene reported, which encode the beta2 integrin family including three frameshift deletions (Tyr382fsX9, Asn282fsX41, and Lys636fsX22), two splicing (IVS4-6C>A, IVS7+1G>A) and three missense (Asp128Tyr, Gly716Ala, and Ala239Thr).[rx]

Additional cause

Mutations in the ITGB2 gene cause leukocyte adhesion deficiency type 1. This gene provides instructions for making one part (the β2 subunit) of at least four different proteins known as β2 integrins. Integrins that contain the β2 subunit are found embedded in the membrane that surrounds white blood cells\ (leukocytes). These integrins help leukocytes gather at sites of infection or injury\, where they contribute to the immune response. β2 integrins recognize signs of inflammation and attach (bind) to proteins called ligands on the lining of blood vessels. This binding leads to linkage (adhesion) of the leukocyte to the blood vessel wall. Signaling through the β2 integrins triggers the transport of the attached leukocyte across the blood vessel wall to the site of infection or injury.

ITGB2 gene mutations that cause leukocyte adhesion deficiency type 1 lead to the production of a β2 subunit that cannot bind with other subunits to form β2 integrins. Leukocytes that lack these integrins cannot attach to the blood vessel wall or cross the vessel wall to contribute to the immune response. As a result, there is a decreased response to injury and foreign invaders, such as bacteria and fungi, resulting in frequent infections, delayed wound healing, and other signs and symptoms of this condition.

Symptoms of Leukocyte Adhesion Deficiency

Diagnosis of Leukocyte Adhesion Deficiency

Typically, diagnosis involves several preliminary tests of immune function, including basic evaluation of the humoral immune system and the cell-mediated immune system. A WBC differential will reveal extremely elevated levels of neutrophils (on the order of 6-10x normal) because they are unable to leave the blood vessels. In the case of LAD-I, a specific diagnosis is done by flow cytometry. This technique will reveal absent or reduced CD18 expression in the leukocyte membrane. Recently, prenatal diagnosis systems have been established, allowing early detection of the disease. LAD-II diagnosis includes the study of different glycosylated forms of the transferrin protein. In LAD-III, as platelet function is also affected, this could be used to differentiate it from the other types

Characteristically, a biopsy of infected tissue demonstrates inflammatory infiltrates completely devoid of neutrophils. Remnants of the umbilical cord can show a loose edematous tissue with remarkably few inflammatory cells. In contrast, there is an elevated level of peripheral blood leucocytes (over 29000/microliters) due to an impaired mobilization of leukocytes to extravascular sites of inflammation.[rx]

History and Physical

The classic presentation of leukocyte adhesion deficiency is recurrent bacterial infections, neutrophil adhesion defects, and umbilical cord sloughing delays. The adhesion defects result in poor leukocyte chemotaxis, particularly the neutrophil, with an inability to form pus and neutrophilia.

Individuals with leukocyte adhesion deficiency commonly suffer from bacterial infections beginning in the neonatal period. Infections such as omphalitis, pneumonia, gingivitis, and peritonitis are common and usually life-threatening due to the inability to destroy the invading pathogens. Individuals with LAD do not form abscesses because granulocytes cannot migrate to the sites of infection.

Characteristics of patients with LAD include the following[rx][rx][rx]:

LAD I:

• Delayed separation of the umbilical cord
• Recurrent pyogenic infections, with onset in the first weeks of life
• Infections caused meanly by Staphylococcus aureus and Pseudomonas aeruginosa
• Absent pus formation
• Periodontitis

LAD II:

• Recurrent skin infections
• Pneumonia
• Bronchiectasis
• Tuberculosis
• Denture abnormalities
• Infections are less severe and fewer as compared to LAD I

LAD III:

• Omphalitis
• Osteoporosis like bone features
• Bleeding complications
• Hematological abnormalities, e.g., bone marrow failure

Other miscellaneous manifestations may include:

• Vaginitis
• Peritonitis
• Osteomyelitis
• Perianal abscesses
• Sinusitis
• Tracheobronchitis
• Necrotic soft tissue infections
• Otitis media
• Meningitis
• Graft versus host reaction
• Recurrent tonsillitis
• Conjunctivitis
• Granuloma
• Oral candidiasis
• Aphthous stomatitis
• Urinary tract infections
• Lymphocytic interstitial pneumonitis
• Glomerulonephritis
• Hemolytic-uremic syndrome
• Nail dystrophy
• Persistent Hyperinsulinemic hypoglycemia of infancy
• Pyoderma gangrenosum
• Megakaryocytic acute myeloid leukemia

The immunological investigation of a patient with leukocyte adhesion deficiency includes[rx][rx][rx]:

Flow Cytometry Analysis (definitive test):

• Demonstrates the absence of functional CD18 and the associated alpha subunit molecules on the surface of leukocytes using CD11 and CD18 monoclonal antibodies (LAD I)
• Demonstrates the absence of sialyl Lewis X expression (CD15a) using a monoclonal antibody directed against sialyl Lewis X ( LAD-II)

Sequence analysis using genetic testing.

• To define the exact molecular defect in the beta-2 subunit

Quantitative Serum Immunoglobulins.

• IgG
• IgM
• IgA
• IgE

Antibody Activity. 

IgG antibodies (post-immunization)

• Tetanus toxoid
• Diphtheria toxoid
• Pneumococcal polysaccharide
• Polio

IgG antibodies (post-exposure)

• Rubella
• Measles
• Varicella Zoster

Detection of isohemagglutinins (IgM)

• Anti-type A blood
• Anti-type B blood

Other assays

• Test for heterophile antibody
• Anti-streptolysin O titer
• Immunodiagnosis of infectious diseases (HIV, hepatitis B, and C, HTLV and dengue)
• Serum protein electrophoresis

Blood lymphocyte subpopulations

• Total lymphocyte count
• T lymphocytes (CD3, CD4, and CD8)
• B lymphocytes (CD19 and CD20)
• CD4/CD8 ratio

Lymphocyte stimulation assays

• Phorbol ester and ionophore
• Phytohemagglutinin
• Antiserum to CD3
• Chemotaxis of human lymphocytes

Phagocytic function

Nitroblue tetrazolium (NBT) test (before and after stimulation with endotoxin)

• Unstimulated
• Stimulated

Neutrophil mobility

• In medium alone
• In the presence of chemoattractant
• In vivo and in vitro chemotaxis of granulocytes

Complement System Evaluation

Measurement of individuals components by immunoprecipitation tests, ELISA, or Western blotting

• C3 serum levels
• C4 serum levels
• Factor B serum levels
• C1 inhibitor serum levels

Hemolytic assays

• CH50
• CH100

Complement system functional studies

• Classical pathway assay (using IgM on a microtiter plate)
• Alternative pathway assay (using LPS on a microtiter plate)
• Mannose pathway assay (using mannose on a microtiter plate)

Microbiological studies

• Nasopharyngeal swab (testing for Rhinovirus)
• Stool (testing for viral, bacterial or parasitic infection)
• Sputum (bacterial culture and pneumocystis PCR)
• Blood (bacterial culture, HIV by PCR, HTLV testing)
• Urine (testing for cytomegalovirus and proteinuria)
• Cerebrospinal fluid (culture, chemistry, and histopathology)

Other investigations of immunodeficiency disorders

• Bone marrow biopsy
• Complete blood cell count
• Blood chemistry
• Histopathological studies
• Tumoral markers
• Levels of cytokines
• Chest x-ray
• Diagnostic ultrasound
• Liver function test

Laboratory Testing

• Initial screening
  • General immunodeficiency screening
    • CBC with differential
    • Comprehensive metabolic profile
    • Quantitative serum immunoglobulins (IgA, IgG, IgM)
    • Lymphocyte subset analyses – depending on clinical presentation
  • Rule out other diseases associated with immunodeficiency
    • HIV-1,2 testing
    • Plasma cell disorders – monoclonal protein detection, quantitation, and characterization with serum protein electrophoresis (SPEP), immunofixation electrophoresis (IFE), IgA, IgG, IgM
    • Cystic fibrosis – sweat chloride testing using an accredited cystic fibrosis center
  • Rule out diseases associated with protein losses (eg, protein-losing enteropathy, nephropathy)
• More specific screening – based on initial screening results
  • Clinical presentation may require multiple immune system investigations (refer to the Immunodeficiency Evaluation for Chronic Infections in Adults and Older Children Testing Algorithm and Immunodeficiency Evaluation for Chronic Infections in Infants and Children Testing Algorithm)
  • Definitive diagnosis, prognostication, genetic counseling, and treatment may require genetic testing
  • Complement testing
• Flow cytometric analysis
  • Assess the presence of beta 2 (β2) integrins CD11 and CD18
    • Decreased/absent expression of CD11/CD18 – consistent with leukocyte adhesion deficiency-1 (LAD1)
      • 2-10% expression – moderate deficiency; reasonable survival rate into adulthood
      • >10% expression – mild deficiency; may not be recognized until late teen years
      • <2% – severe deficiency; majority die in infancy unless bone marrow transplant is performed
    • Normal expression of CD11/CD18 – consistent with LAD2 or LAD3
  • Assess the presence of CD15 – indicated if LAD2 is suspected
    • Absent expression of CD15 – consistent with LAD2
  • Another testing
    • Neutrophil rolling, neutrophil adherence, neutrophil motility – performed only in specialized laboratories
    • Bombay blood group phenotype testing – present in LAD2
    • Platelet aggregation – abnormal in LAD3
    • Molecular sequence analysis – defines exact molecular defect

Differential Diagnosis

• Sepsis
• Neutropenic disorders
• Agranulocytosis
• IRAK-4 deficiency
• Job syndrome
• Chronic granulomatous disease
• Myeloperoxidase deficiency
• Congenital disorders of glycosylation
• Leukemoid reaction in infants
• Other congenital coagulation disorders (particularly in LAD3 due to bleeding tendency)

Treatment of Leukocyte Adhesion Deficiency

• The treatment of LAD-I is an allogeneic hematopoietic stem cell transplant (HSCT). By the age of 2 years, the disease is fatal in severe cases without HSCT.[rx][rx][rx]
• Ustekinumab, a monoclonal antibody of the p40 subunit common to IL-12 and IL-23, had been used successfully to treat refractory periodontitis and sacral ulcer in a case report with mild LAD I.[rx] However, further studies are necessary to determine safety and efficacy, particularly in patients with more severe diseases.
• Recombinant human interferon-gamma treatment has been used in LAD-I. [rx]
• A trial of fucose supplementation is recommended in all patients diagnosed with LAD II[rx]
• Recombinant factor VIIa is considered effective in treating and preventing severe bleeding in a child patient with LAD III [rx]
• The use of prophylactic immunoglobulin therapy was successful in two patients with a severe form of LAD.[rx]
• More conservative treatment is directed against specific infectious agents. Patients are infected with common pathogenic agents but no with opportunistic ones and should respond well to antimicrobial therapy. The most common pathogens affecting patients with LAD include Proteus, Klebsiella, Staphylococcus aureus, Pseudomonas aeruginosa, and enterococci.  Early aggressive treatment should be used or given as prophylactic therapy (e.g., dental procedures).
• Although patients can receive intensive antibiotherapy and even granulocyte transfusions from healthy donors, the only current curative therapy is the hematopoietic stem cell transplant.^[rx] However, progress has been made in gene therapy, an active area of research. Both foamy viral and lentiviral vectors expressing the human ITGB2 gene under the control of different promoters have been developed and have been tested so far in preclinical LAD-I models (such as CD18-deficient mice and canine leukocyte adhesion deficiency-affected dogs).

References