Role of bacteria in leukocyte adhesion deficiency-associated periodontitis.

Leukocyte adhesion deficiency Type I (LAD-I)-associated periodontitis is an aggressive form of inflammatory bone loss that has been historically attributed to lack of neutrophil surveillance of the periodontal infection. However, this form of periodontitis has proven unresponsive to antibiotics and/or mechanical removal of the tooth-associated biofilm. Recent studies in LAD-I patients and relevant animal models have shown that the fundamental cause of LAD-I periodontitis involves dysregulation of a granulopoietic cytokine cascade. This cascade includes interleukin IL-23 (IL-23) and IL-17 that drive inflammatory bone loss in LAD-I patients and animal models and, moreover, foster a nutritionally favorable environment for bacterial growth and development of a compositionally unique microbiome. Although the lack of neutrophil surveillance in the periodontal pockets might be expected to lead to uncontrolled bacterial invasion of the underlying connective tissue, microbiological analyses of gingival biopsies from LAD-I patients did not reveal tissue-invasive infection. However, bacterial lipopolysaccharide was shown to translocate into the lesions of LAD-I periodontitis. It is concluded that the bacteria serve as initial triggers for local immunopathology through translocation of bacterial products into the underlying tissues where they unleash the dysregulated IL-23-IL-17 axis. Subsequently, the IL-23/IL-17 inflammatory response sustains and shapes a unique local microbiome which, in turn, can further exacerbate inflammation and bone loss in the susceptible host.

Frontline Science: Activation of metabolic nuclear receptors restores periodontal tissue homeostasis in mice with leukocyte adhesion deficiency-1.

ß2 Integrins mediate neutrophil-endothelial adhesion and recruitment of neutrophils to sites of inflammation. The diminished expression of ß2 integrins in patients with mutations in the ITGB2 (CD18) gene (leukocyte adhesion deficiency-Type 1; LAD1) results in few or no neutrophils in peripheral tissues. In the periodontium, neutrophil paucity is associated with up-regulation of IL-23 and IL-17, which drive inflammatory bone loss. Using a relevant mouse model, we investigated whether diminished efferocytosis (owing to neutrophil scarcity) is associated with LAD1 periodontitis pathogenesis and aimed to develop approaches to restore the missing efferocytosis signals. We first showed that CD18-/- mice phenocopied human LAD1 in terms of IL-23/IL-17-driven inflammatory bone loss. Ab-mediated blockade of c-Mer tyrosine kinase (Mer), a major efferocytic receptor, mimicked LAD1-associated up-regulation of gingival IL-23 and IL-17 mRNA expression in wild-type (WT) mice. Consistently, soluble Mer-Fc reversed the inhibitory effect of efferocytosis on IL-23 expression in LPS-activated Mϕs. Adoptive transfer of WT neutrophils to CD18-/- mice down-regulated IL-23 and IL-17 expression to normal levels, but not when CD18-/- mice were treated with blocking anti-Mer Ab. Synthetic agonist-induced activation of liver X receptors (LXR) and peroxisome proliferator-activated receptors (PPAR), which link efferocytosis to generation of homeostatic signals, inhibited the expression of IL-23 and IL-17 and favorably affected the bone levels of CD18-/- mice. Therefore, our data link diminished efferocytosis-associated signaling due to impaired neutrophil recruitment to dysregulation of the IL-23-IL-17 axis and, moreover, suggest LXR and PPAR as potential therapeutic targets for treating LAD1 periodontitis.

Root surface characteristics of children teeth with periodontal diseases.

The present study examined the root surfaces of teeth from children with or without periodontal diseases and with or without systemic diseases. Light microscopy revealed that when compared to control teeth: teeth with chronic periodontitis had similar radicular histology; teeth from children with leukocyte adhesion deficiency, Down syndrome and aggressive periodontitis had narrower cementum areas; teeth from children with hypophosphatasia showed cementum aplasia. Cementum anomalies may facilitate the establishment and progress of periodontitis in children.

Molecular basis of leukocyte adhesion molecules in early-onset periodontitis patients with decreased CD11/CD18 expression on leukocytes.

We analyzed the cell-cell adherence related to CD11/CD18 and CD18 mRNA in individuals with decreased CD11/CD18 expression on their neutrophil surface. Epstein Barr virus-transformed B cell lines were developed from one localized juvenile periodontitis (LJP) patient with decreased CD11/CD18 in the peripheral blood neutrophils and without systemic diseases; two siblings with generalized prepubertal periodontitis (GPP) caused by leukocyte adhesion deficiency (LAD); another LJP patient; one localized prepubertal periodontitis (LPP) patient; and two healthy subjects. Adhesion of leukocytes to each other was measured as cluster formation by aggregation assay. The length and the amount of CD18 mRNA expressed in the cell lines were analyzed by Northern blotting using the 32P-labeled CD18 cDNA. The coding region of the mRNA was analyzed by the reverse transcription-polymerase chain reaction method. Base-mismatches between CD18 mRNA and the 32P-labeled RNA probe synthesized from CD18 cDNA were analyzed by RNase protection assay. In the adherence assay, cells from the LJP patients with decreased CD11/CD18 formed more clusters of smaller size and fewer cells than those of the other subjects. The cells from GPP and LAD patients did not aggregate and did not form clusters either in the absence or presence of PMA. There were no differences in the length and the amount of mRNA between the LJP patients and the other subjects, while GPP-LAD patients expressed a small amount of long mRNA. The whole coding region (2,313 base pairs) of all subjects was amplified except for the GPP-LAD patients, and the 5'-region (1,119 base pairs) was amplified from all subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiographic and immunohistochemical analysis of leukocyte adhesion deficiency in Holstein heifers.

Radiographic and immunohistochemical analyses were performed in two Holstein heifers with leukocyte adhesion deficiency (BLAD). Severe bone resorption, osteolysis and severe progressive periodontitis in submandibula due to dysfunction of leukocytes in heifers affected with BLAD were demonstrated by radiographic examination. Immunohistochemical analysis of lymph nodes using anti-CD18 monoclonal antibody demonstrated that CD18-positive cells were not found on those from a heifer affected with BLAD, whereas CD18-positive cells were clearly present in lymph nodes from a clinically normal heifer. These characteristic findings support the importance of adherence-dependent leukocyte functions in host defense.

Bovine leukocyte adhesion deficiency (BLAD): a review.

Bovine leukocyte adhesion deficiency (BLAD) in Holstein cattle is an autosomal recessive congenital disease characterized by recurrent bacterial infections, delayed wound healing and stunted growth, and is also associated with persistent marked neutrophilia. The molecular basis of BLAD is a single point mutation (adenine to guanine) at position 383 of the CD18 gene, which caused an aspartic acid to glycine substitution at amino acid 128 (D128G) in the adhesion molecule CD18. Neutrophils from BLAD cattle have impaired expression of the beta2 integrin (CD11a,b,c/CD18) of the leukocyte adhesion molecule. Abnormalities in a wide spectrum of adherence dependent functions of leukocytes have been fully characterized. Cattle affected with BLAD have severe ulcers on oral mucous membranes, severe periodontitis, loss of teeth, chronic pneumonia and recurrent or chronic diarrhea. Affected cattle die at an early age due to the infectious complications. Holstein bulls, including carrier sires that had a mutant BLAD gene in heterozygote were controlled from dairy cattle for a decade. The control of BLAD in Holstein cattle by publishing the genotypes and avoiding the mating between BLAD carriers was found to be successful. This paper provides an overview of the genetic disease BLAD with reference to the disease in Holstein cattle.

Defective neutrophil recruitment in leukocyte adhesion deficiency type I disease causes local IL-17-driven inflammatory bone loss.

Leukocyte adhesion deficiency type I (LAD-I), a disease syndrome associated with frequent microbial infections, is caused by mutations on the CD18 subunit of ß2 integrins. LAD-I is invariably associated with severe periodontal bone loss, which historically has been attributed to the lack of neutrophil surveillance of the periodontal infection. We provide an alternative mechanism by showing that the cytokine interleukin-17 (IL-17) plays a major role in the oral pathology of LAD-I. Defective neutrophil recruitment in LAD-I patients or in LFA-1 (CD11a/CD18)-deficient mice--which exhibit the LAD-I periodontal phenotype--was associated with excessive production of predominantly T cell-derived IL-17 in the periodontal tissue, although innate lymphoid cells also contributed to pathological IL-17 elevation in the LFA-1-deficient mice. Local treatment with antibodies to IL-17 or IL-23 in LFA-1-deficient mice not only blocked inflammatory periodontal bone loss but also caused a reduction in the total bacterial burden, suggesting that the IL-17-driven pathogenesis of LAD-I periodontitis leads to dysbiosis. Therefore, our findings support an IL-17-targeted therapy for periodontitis in LAD-I patients.

Observations of root surfaces from patients with early-onset periodontitis and leukocyte adhesion deficiency.

The purpose of this investigation was to report observations of the root surfaces of teeth from 2 siblings with leukocyte adhesion deficiency (LAD). In previous publications, the clinical, radiographic and immunologic findings in the family were presented. 38 permanent teeth from the 2 siblings were prepared for microscopic examination, 11 for light microscopy (LM), and 27 for scanning electron microscopy (SEM). In addition, 8 healthy teeth obtained from 2 patients requiring extractions for orthodontic treatment served as controls. LM observations on healthy teeth revealed cementum with normal structural appearance which exhibited a mosaic or mogul-like pattern with SEM. In LAD specimens, cementum apical to the dentogingival junction exhibited resorption lacunae and areas of poor structural definition characterized by aplasia and hypoplasia (hypomineralization). Areas of hypoplasia presented as distinct irregular surfaces with a pebbly or globular-like appearance. Alteration in cementum formation and maturation may play a role in the etiology of early-onset periodontitis.