An inherited abnormality of neutrophil adhesion. Its genetic transmission and its association with a missing protein

Dizygotic twin sisters with myelokathexis: mechanism of its neutropenia

Dizygotic twin sisters were first found to have neutropenia at 1 year of age when evaluated for recurrent pulmonary infections. Since then they have remained neutropenic (0.05 approximately 0.5 x 10(9)/l). Despite of their neutropenia, myeloid hyperplasia was evident on a marrow smear examination, and a number of cells were hypersegmented with fine interlobular bridging with chromatin strands and cytoplasmic vacuolation. Electron microscopy showed apoptotic cells with condensed nuclei and apoptotic bodies in the cytoplasm. Although life span, hydrogen peroxide production, phagocytosis, spreading, and chemotaxis of peripheral neutrophils were normal, the survival of bone marrow neutrophils in both infants was markedly decreased when compared with that of normal bone marrow neutrophils. During the bone marrow culture apoptotic neutrophils were observed at an earlier stage in both patients than in normal controls, biochemically and morphologically. Morphology of bone marrow neutrophils in both patients resembled that of cultured control bone marrow neutrophils. Peripheral neutropenia and appearance of characteristic neutrophils in the bone marrow in myelokathexis are considered to be an expression of apoptosis of bone marrow neutrophils.

Integrin signalling in neutrophils and macrophages

Integrins have been characterized extensively as adhesion receptors capable of transducing signals inside the cell. In myelomonocytic cells, integrin-mediated adhesive interactions regulate different selective cell responses, such as transmigration into the inflammatory site, cytokine secretion, production or reactive oxygen intermediates, degranulation and phagocytosis. In the last few years, great progress has been made in elucidating mechanisms of signal transduction by integrins in neutrophils and macrophages. This review summarises the current information on the role of integrins in regulating myelomonocytic cell functions and highlights the signalling pathways activated by integrin engagement in these cells. Also, exploiting the current knowledge of mechanisms of integrin signal transduction in other cell types, we propose a model to explain how integrins transduce signals inside neutrophils and macrophages, and how signaling pathways leading to regulation of selective cell functions may be coordinated.

Leukocyte adhesion deficiency in a child with severe oral involvement

Leukocyte adhesion deficiency is a rare inherited defect of phagocytic function resulting from a lack of leukocyte cell surface expression of beta2 integrin molecules (CD11 and CD18) that are essential for leukocyte adhesion to endothelial cells and chemotaxis. A small number of patients with leukocyte adhesion deficiency-1 have a milder defect, with residual expression of CD18. These patients tend to survive beyond infancy; they manifest progressive severe periodontitis, alveolar bone loss, periodontal pocket formation, and partial or total premature loss of the primary and permanent dentitions. We report on a 13-year-old boy with moderate leukocyte adhesion deficiency-1 and severe prepubertal periodontitis. This case illustrates the need for the dentist to work closely with the pediatrician in the prevention of premature tooth loss and control of oral infection in these patients.

Influence of age and plasma treatment on neutrophil phagocytosis and CD18 expression in foals

The aim of this study was to evaluate the influence of age and plasma treatment on neutrophil phagocytosis, CD18 expression and serum opsonic capacity in foals in field settings. Microbial infections constitute a large threat in young foals and neutrophil functions are crucial for the defense. Blood samples were obtained from 13 foals at seven time points between the ages of 2 and 56 days and once from 16 adult horses. Six of the foals were treated with adult plasma at the age of 1 week. Neutrophil phagocytosis of yeast after various opsonizations and the expression of complement adhesion receptor CD18 were analysed by flow cytometry. Autologous serum opsonization resulted in 52+/-6.1% phagocytic neutrophils in 2-day-old foals (n = 12), a significantly lower rate than in adult horses (mean 84+/-3.1%; n = 16). In foals, yeast ingestion per neutrophil was also lower than in adults. Opsonic capacity increased with age (p < 0.05), reaching adult levels at 3-4 weeks. An increase in serum opsonic capacity followed plasma treatment (p < 0.05). The phagocytic capacity of foal neutrophils at the time-points studied was equal to or higher than that in the adults, when pooled adult horse serum or anti-yeast IgG was used as opsonin. In foals, serum IgG concentration was negatively correlated to serum opsonic capacity. CD18 receptor expression was higher in neutrophils from foals (<21 days old) than in those from adult horses (p < 0.05). The results indicate that foals are transiently deficient in serum opsonic capacity, which negatively affects their capacity for neutrophil phagocytosis. These changes in serum opsonins, unrelated to IgG, may be important factors in susceptibility to infections in foals.

Autoantibodies to leukocyte alphaMbeta2 integrin glycoproteins in HIV infection

HIV infection is often associated with polyclonal B-cell activation, autoantibodies, and clinically evident autoimmune disease. Because neutropenia and anti-neutrophil autoantibodies are common clinical features of HIV disease, we studied a series of HIV+ patients to determine whether anti-alphaMbeta2 integrin (MAC-1) specific anti-neutrophil autoantibodies occur in HIV disease, as we have shown to occur in patients with immune neutropenia not associated with HIV. Two new assays specific for anti-alphaMbeta2 IgG were developed to carry out these studies: an ELISA method using affinity-purified alphaMbeta2 integrin protein, and a flow cytometry method using subclones of the 293 human fetal kidney cell line, stably transfected with cDNAs for the alphaM and/or beta2 integrin subunits. In studies of the sera of 20 untreated HIV+ individuals, anti-alphaMbeta2 activity was detected in 9 (45%) by one or the other of these assays and in 5 (25%) by both assays. Seven of the 20 HIV+ study subjects had unexplained neutropenia, and of these, 6 (86%) were positive for anti-alphaMbeta2 autoantibodies. Our findings indicate that anti-alphaMbeta2 integrin autoantibodies are frequent in HIV+ individuals, particularly when unexplained neutropenia is also present, and raise the possibility that these autoantibodies may have a role in the acquired neutrophil dysfunction and increased risk of nonopportunistic bacterial infections observed in HIV disease.

Activation of p47(PHOX), a cytosolic subunit of the leukocyte NADPH oxidase. Phosphorylation of ser-359 or ser-370 precedes phosphorylation at other sites and is required for activity

The leukocyte NADPH oxidase catalyzes the reduction of oxygen to superoxide (O-2) at the expense of NADPH in phagocytes and B lymphocytes. The enzyme is dormant in resting cells but becomes active when the cells are exposed to appropriate stimuli. During oxidase activation, the highly basic cytosolic oxidase component p47(PHOX) becomes phosphorylated on several serines and migrates to the plasma membrane. We report here that p47(PHOX)-deficient B lymphoblasts expressing the p47(PHOX) S359A/S370A or p47(PHOX) S359K/S370K double mutation show dramatically reduced levels of enzyme activity and phosphorylation of p47(PHOX) as compared with the same cells expressing wild type p47(PHOX). In addition, these mutant p47(PHOX) proteins fails to translocate to the plasma membrane when the cells are stimulated. In contrast, normal phosphorylation and translocation are seen in mutants containing aspartate or glutamate at positions 359 and 370, but oxidase activity is still greatly reduced. These results imply that a negative charge at position 359 and/or 370 is sufficient to allow the phosphorylation and translocation of p47(PHOX) to take place but that features unique to a phosphorylated hydroxyamino acid are required to support O-2 production. These findings, plus those from an earlier study (Inanami, O., Johnson, J. L., McAdara, J. K., El Benna, J., Faust, L. P., Newburger, P. E., and Babior, B. M. (1998) J. Biol. Chem. 273, 9539-9543), suggest that oxidase activation requires 1) the sequential phosphorylation of at least two serines on p47(PHOX): Ser-359 or Ser-370, followed by Ser-303 or Ser-304; and 2) the translocation of p47(PHOX) to the membrane at some point after the first phosphorylation takes place.

Genetic aspects of dental disorders

This paper reviews past and present applications of quantitative and molecular genetics to dental disorders. Examples are given relating to craniofacial development (including malocclusion), oral supporting tissues (including periodontal diseases) and dental hard tissues (including defects of enamel and dentine as well as dental caries). Future developments and applications to clinical dentistry are discussed. Early investigations confirmed genetic bases to dental caries, periodontal diseases and malocclusion, but research findings have had little impact on clinical practice. The complex multifactorial aetiologies of these conditions, together with methodological problems, have limited progress until recently. Present studies are clarifying previously unrecognized genetic and phenotypic heterogeneities and attempting to unravel the complex interactions between genes and environment by applying new statistical modelling approaches to twin and family data. Linkage studies using highly polymorphic DNA markers are providing a means of locating candidate genes, including quantitative trait loci (QTL). In future, as knowledge increases; it should be possible to implement preventive strategies for those genetically-predisposed individuals who are identified to be at risk.

Pediatric umbilical problems

After birth, the normal umbilicus is a relatively simple structure. During the development of the embryo, however, this region is highly complex. Vestigial of the umbilical cord can be responsible for umbilical inflammation and drainage. This article reviews the embryology of the umbilicus and discusses a number of clinical problems seen in this area. The authors' aim is to aid the primary care pediatrician in evaluating, treating, and appropriately referring umbilical problems encountered in office practice.

Leucocyte adhesion deficiency presenting as a chronic ileocolitis

CD11/CD18 leucocyte glycoprotein deficiency is a rare, congenital adhesion molecule disorder which, in its severe form, is usually fatal. Leucocytes in affected subjects have abnormal migration and adherence, rendering patients susceptible to life threatening infections. The CD11/CD18 integrins, and other adhesion molecules, are considered essential to the normal inflammatory response. It has been postulated that adhesion molecules may be responsible for mediating in part, the inflammatory changes observed in inflammatory bowel diseases and related disorders. This report describes the first case of CD11/CD18 deficiency characterised by a chronic ileocolitis. Bone marrow transplantation completely resolved the gastrointestinal symptoms, supporting a role for neutrophil dysfunction in the pathogenesis of the gut lesions. This case suggests that specific blockade of CD11/CD18 integrins alone may not halt the chronic inflammatory response observed in immune mediated bowel disorders, and that abnormalities of leucocyte function must be included in the differential diagnosis of paediatric Crohn's disease.

Apoptosis following interleukin-2 withdrawal from T cells: evidence for a regulatory role of CD18 (beta 2-integrin) molecules

Following a successful immune response against invading microorganisms, the majority of activated T cells is eliminated, while a minor fraction survives as memory T cells. A decline in T lymphocyte growth factors such as interleukin-2 (IL-2) appears to play a role in the elimination of previously activated T cells. Thus, removal of IL-2 from proliferating T cells not only induces growth arrest, but triggers a massive cell death due to apoptosis. While the apoptotic response involves a series of well-described events, it remains less clear how apoptosis is regulated following IL-2 withdrawal. Here, we provide evidence that CD18 molecules (beta 2-integrins) play a regulatory role in the apoptotic response following removal of IL-2 from previously activated, antigen specific CD4+ T cell lines. Thus, CD18 mAb inhibited the apoptotic response to IL-2 deprivation, whereas mAb against other adhesion molecules (CD28, CD29, CD49d, CD80, CD86) did not. Secondly, IL-2 withdrawal resulted in a retarded apoptotic response in LFA-1 (CD11a/CD18) negative T cells obtained from a leukocyte adhesion deficiency (LAD) patient, as compared to LFA-1 positive T cell lines. Thirdly, co-culture of LFA-1 positive- and negative-T cells at different ratios induced apoptotic responses that were higher than expected, had the two lymphocyte populations not been interacting and significantly higher than that seen in pure LFA-1 negative T cells. Supernatants from LFA-1 positive T cell cultures undergoing apoptosis did not induce an enhanced apoptotic responses in LFA-1 negative T cells, and, reversely, culture supernatants from LFA-1 negative T cells did not rescue LFA-1 positive cells from undergoing apoptosis. The apoptotic response was partly blocked by IL-15, a newly identified T cell growth factor. Taken together, these findings suggest that CD18 molecules (beta 2-integrins) play a regulatory role in the apoptotic response following cytokine withdrawal, and that the regulation is mediated, at least partly, through T-T cell interactions. Thus, apoptotic death following IL-2 deprivation appears to be under "social" control by surrounding T cells.

The phosphorylation targets of p47phox, a subunit of the respiratory burst oxidase. Functions of the individual target serines as evaluated by site-directed mutagenesis

The respiratory burst oxidase of phagocytes and B lymphocytes catalyzes the reduction of oxygen to O2- at the expense of NADPH. Dormant in resting cells, the oxidase is activated by exposing the cells to appropriate stimuli. During activation, p47phox, a cytosolic oxidase subunit, becomes extensively phosphorylated on a number of serines located between S303 and S379. To determine whether this phosphorylation is necessary for oxidase activation, we examined phorbol-elicited oxidase activity in EBV-transformed B lymphoblasts deficient in p47phox after transfection with plasmids expressing various S-->A mutants of p47phox. The mutant containing S-->A mutations involving all serines between S303 and S379 [S(303-379)A] was not phosphorylated, did not translocate to plasma membrane during activation and was almost devoid of function. As to individual serines, S379 was of special interest because (a) p47 phox S379 was phosphorylated in phorbol-activated lymphoblasts expressing wild-type p47phox, and (b) p47phox S379A failed to translocate to the membrane, and was as functionless as p47phox S(303-379)A; other single S-->A mutations had little effect on oxidase activity. These findings suggest that the phosphorylation of S379 may be important for oxidase activation in whole cells.

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.

Genetic and heritable risk factors in periodontal disease

The purpose of this paper is to review current knowledge of genetic risk factors for the periodontal diseases and to present updated and additional data from the Minnesota Twin Periodontal Study. Family studies suggest that susceptibility to the early onset forms of disease, particularly prepubertal and juvenile periodontitis, is, at least in part, influenced by host genotype. Inherited phagocytic cell deficiencies appear to confer risk for prepubertal periodontitis. The prevalence and distribution of juvenile periodontitis in affected families are most consistent with an autosomal recessive mode of inheritance. However, considerable etiologic as well as genetic heterogeneity within these clinically-defined diseases is evident. Whether or not genetic factors influence the more common adult chronic periodontitis is less clear. Although results from family studies suggest that environmental factors appear to be the major determinants of variance in adult periodontitis, data from our twin studies indicate that both genetic and environmental factors influence disease. Furthermore, comparisons between reared-together and reared-apart adult monozygous twins indicate that early family environment has no appreciable influence on probing depth and attachment loss measures in adults.

Cell adhesion molecules in inflammation and immunity: relevance to periodontal diseases

Inflammatory and immune responses involve close contact between different populations of cells. These adhesive interactions mediate migration of cells to sites of inflammation and the effector functions of cells within the lesions. Recently, there has been significant progress in understanding the molecular basis of these intercellular contacts. Blocking interactions between cell adhesion molecules and their ligands has successfully suppressed inflammatory reactions in a variety of animal models in vivo. The role of the host response in periodontal disease is receiving renewed attention, but little is known of the function of cell adhesion molecules in these diseases. In this review we summarize the structure, distribution, and function of cell adhesion molecules involved in inflammatory/immune responses. The current knowledge of the distribution of cell adhesion molecules is described and the potential for modulation of cell adhesion molecule function is discussed.

Involvement of the pertussis toxin-sensitive GTP-binding protein in regulation of expression and function of granulocyte complement receptor type 1 and type 3

Human polymorphonuclear leukocytes (PMN) express receptors for complement (C) C3b and C3bi termed CR1 and CR3, respectively. The addition of PMA or fMLP to PMN enhances the capacity of these receptors to promote binding of C3b- and C3bi-coated erythrocytes. fMLP-dependent increase of the binding of these ligand-coated erythrocytes was completely abolished by prior exposure of the PMN to pertussis toxin (IAP). GTP-binding protein (Gi alpha) was ADP-ribosylated and dysfunctional by this treatment. On the other hand, PMA-dependent binding of these ligands, as well as control binding, was inhibited only slightly, if at all, by the IAP treatment. The levels of C receptor expression on cell surface were determined by flow cytometry using monoclonal antibody against CR1 and those against the alpha and beta chains of CR3 (CR3 is composed of alpha and beta chain). Upon exposure of PMN to the chemotactic factor or PMA, or upon incubation of the cells at 37 degrees C, the surface expression of CR1 and CR3 alpha was increased. IAP also blocked an fMLP-induced increase of CR1 and CR3 alpha, but did not block the temperature- or PMA-dependent increase of these receptors. Opsonized zymosan (SOZ), another ligand for CR3, also led to an increase of both CR1 and CR3 alpha. Neither PMA nor SOZ brought about an increase of the surface expression of CR3 beta, but fMLP caused a slight increase of CR3 beta in an IAP-sensitive manner. Based on the IAP-sensitivity of the receptor expression, therefore, it appears that at least two separate mechanisms are operative in the control of C receptors. In addition, the alpha and beta chains of CR3 are regulated independently. The present data offer evidence suggesting that C receptor functions are in part regulated through a GTP-binding protein via modulation of their surface expression.

Impairment of raw 264.7 macrophage function by antiarrhythmic drugs

The effect of the antiarrhythmic drugs lidocaine, quinidine and procainamide on macrophage function was investigated in RAW 264.7 mouse monocytic macrophage cell. Cells stimulated by either zymosan or phorbol ester were found to generate both superoxide (O2-) and H2O2. The production of O2 was detected as superoxide dismutase inhibitable ferricytochrome c reduction. H2O2 production was monitored in both chemical and flow cytometric fluorescent assays. Although all three drugs inhibited both O2 and H2O2 release in a dose-dependent manner, only quinidine was found to have significant inhibitory effects. The amounts of quinidine required to cause a 50% inhibition in O2 production in zymosan and phorbol ester stimulated cells were found to be 250 microM and 300 microM, respectively and the amounts required to cause one-half optimum levels of H2O2 production in these cells were found to be 50 microM and 100 microM, respectively. The effect of these drugs on O2 producing NADPH oxidase was investigated and only procainamide was found to have a significant effect (p < 0.001) in inhibiting the oxidase activity. Lidocaine and quinidine had no significant effect on the activation of the respiratory burst oxidase. A sensitive and convenient 'differential phagocytosis' assay was devised on the basis of number of particles engulfed by individual phagocytes using flow cytometric techniques. It appears to be remarkably free of interference and was applied to investigate the role of antiarrhythmic drugs on the phagocytosis of fluorescent latex beads. All three antiarrhythmic drugs inhibited phagocytosis of latex beads in a dose dependent manner irrespective of the number of particles phagocitized by the cells. The results of these studies do not conclusively establish a mechanism of action of these drugs on the generation of O2 and H2O2 by stimulated macrophages; nevertheless, it is interesting that all three drugs inhibited the phagocytic activity.

Neutrophil recruitment in Clostridium difficile toxin A enteritis in the rabbit

Neutrophil infiltration is a prominent feature of Clostridium difficile-associated enteritis and colitis. The aim of this study was to examine the importance of neutrophil recruitment and neutrophil-mediated tissue damage in C. difficile toxin A-induced enteritis. Competitive binding experiments using purified 3H-toxin A demonstrated the presence of a single class of medium affinity receptors on rabbit neutrophils (Kd 7 x 10(-8) M). Pertussis toxin and the nonhydrolyzable GTP analog GTPgamma S both inhibited 3H-toxin A binding (by 56 and 65%, respectively), indicating that the rabbit neutrophil toxin A receptor is G protein linked. Toxin A elicited a dose-dependent (25-200 micrograms/ml) stimulation of neutrophil migration in vitro, and this functional effect was also pertussis toxin sensitive (69% inhibition). Treatment of neutrophils with R15.7, a blocking monoclonal antibody to the leuocyte adhesion molecule CD18, inhibited toxin A-stimulated neutrophil migration by 85% in vitro. Pretreatment of rabbits with R15.7 also prevented neutrophil infiltration of toxin A-exposed ileal loops in vivo as determined by histologic examination and by ileal tissue myeloperoxidase levels. Furthermore, R15.7 effected a substantial inhibition of fluid secretion (by 65%), mannitol permeability (by 66%), and histologic damage in toxin A-exposed ileal loops. Anti-CD18 (R15.7) had no inhibitory effect on cholera toxin enterotoxicity. These data demonstrate that C. difficile toxin A is a proinflammatory toxin whose enterotoxic effects are substantially dependent upon neutrophil recruitment.

Chemotaxis of polymorphonuclear neutrophils (PMN) in patients suffering from recurrent infection

PMN function was tested in patients suffering from recurrent infections. In 65 out of 240 patients lack of oxygen radical production or reduced chemotactic activity was found. In most cases the reduction was transient and associated with clinical impairments of the patients. Only a few patients had primary cellular defects. In one of those patients the expression of beta 2 integrins was reduced, while PMN of the other patients expressed beta 2 integrins normally. Thus, cellular defects other than the reduced expression of beta 2 integrins might also result in impaired chemotactic activity.

Leukocyte adhesion deficiency in a Dutch Holstein calf: a case with a clear-cut family history

A leukocyte adhesion deficiency characterized by recurrent (predominantly bacterial) infections, lack of extravascular polymorphonuclear leukocyte (PMN) and pus formation has been described first in humans and then in dogs, and recently also in cattle. Because of important clinical similarities, a unitary explanation for the leukocyte adhesion deficiency (LAD) syndrome in mammals is proposed, inasmuch that an intrinsic leukocyte defect (i.e. mutations in genes encoding the common CD18 subunit), is thought to cause the disease. However, thus far, the hallmark of such intrinsic leukocyte defects, notably their heritability (or familial incidence), has not (yet) been unequivocally demonstrated. This is the first report to describe the occurrence of four Dutch bovine LAD (BLAD) cases with the clearest familial clustering observed to date. The diagnosis was based on the clinical features of very poor thriving, in general, of the calves, hyperneutrocytosis without appreciable left shift, and the absence of PMN CD11a, or CD11b, or CD11c using monoclonal antibodies (mAb) and/or Concanavalin A binding activity of PMN lysates in immunoblots. Interestingly, a familial clustering was observed also for below-normal PMN CD11c expression. Thus, a cow with low CD11c expression (50.4%) and delivering three of the study BLAD calves, also had a healthy descendant with low (44.9%) PMN CD11c expression. These findings suggested the possibility that both subnormal expression and lack of PMN CD11 expression are inheritable factors in cattle. Furthermore, a large prospective study using the present mAb for selecting relatives expressing the complete spectrum (0 to > or = 90%) of PMN CD11/CD18 expression would create a comprehensive study population for understanding both the role of genetic factors and of survival strategies in BLAD.

Spin-trapping and chemiluminescence studies of neutrophils from a Holstein-Friesian calf with bovine leukocyte adhesion deficiency

The ability of neutrophils from a Holstein-Friesian calf with bovine leukocyte adhesion deficiency (the proband with a genetic deficiency of the Mac-1 (CD11b/CD18) glycoprotein corresponding to the receptor of complement iC3b) to generate oxygen radicals was examined using electron spin resonance spectrometry (ESR) combined with a spin-trapping technique and luminol-dependent chemiluminescence spectrometry. When the neutrophils were stimulated with phorbol 12-myristate 13-acetate (PMA), an ESR spectrum confirming the generation of superoxide anions (O2-) was clearly observed in both healthy and diseased calves. However, when the neutrophils were stimulated by opsonized zymosan, appearance of the ESR spectrum was recognized in the healthy calves but not in the diseased calf. Similar results were obtained from chemiluminescence experiments.

Host defense activity in various hosts. Human neutrophil NADPH oxidase activity

The superoxide generation of neutrophil NADPH oxidase from healthy subjects, patients with respiratory infections, and patients receiving effective therapy with antibiotics or steroids was investigated. In young healthy nonsmokers the mean oxidase activity of neutrophils in women was significantly lower than that in men. In healthy women the mean oxidase activity was significantly lower in young nonsmokers than in young smokers or the elderly. In young nonsmokers, oxidase activity significantly increased during respiratory infections; however, in elderly nonsmokers, no significant increase in oxidase activity was observed during respiratory infections. The mean oxidase activity in patients receiving steroids was very low. In in vitro experiments using cell-free activation systems of NADPH oxidase, steroids were found to injure the membrane-bound components of the oxidase enzyme. These results suggest that decreased superoxide generation in patients receiving steroids may result from steroid-induced damage in the membrane-bound components of the NADPH oxidase system. The inhibitory effect of steroids on superoxide production may reduce bactericidal action of neutrophils, ie, one defense mechanism of the body against many kinds of pathogens. Therefore, long-term therapy with steroids in the elderly should be avoided at all costs.

Leukocyte cell adhesion proteins: from molecular dissection to clinical applications

Leukocyte adhesion is needed for a number of leukocyte functions like immunoglobulin synthesis, T and NK-cell-mediated cytotoxicity, phagocytosis by granulocytes, and cellular accumulation in inflamed tissue. Several cell surface molecules involved in leukocyte-leukocyte and leukocyte-target cell interactions have recently been identified and characterized. Both the polypeptide and carbohydrate portions are important in leukocyte interactions. It is becoming increasingly apparent that it is possible to interfere with the normal functions of the leukocyte adhesion glycoproteins, and such applications may become important in medicine.

Leucocyte adhesion protein deficiency in Irish setter dogs

Investigation of 12 Irish setter puppies from six litters with severe recurrent infections, neutrophilia and low body weight revealed a leucocyte adhesion protein deficiency with a total lack of CD11b and CD18. Their neutrophil function was severely impaired with a totally absent capacity to ingest C3b-opsonized particles, a significantly impaired capacity to ingest IgG-opsonized particles and significantly diminished adherence to nylon wool when compared with neutrophils from healthy control dogs. The chemiluminescence of patient neutrophils activated by C3b-opsonized particles was, consequently, significantly decreased compared with that of control neutrophils, while the respiratory burst assayed by phorbolmyristate acid (PMA) stimulated nitroblue tetrazolium (NBT)-reduction was normal in the patient group. Random migration and chemotactic responses of patient and control neutrophils, were similar. The etiology, pathogenesis and clinical manifestations of the Irish setter leucocyte adhesion deficiency were similar to that of the leucocyte adhesion deficiency in humans.

Complement

The complement system mediates a wide range of important biological functions. The use of modern techniques in protein chemistry and molecular biology has greatly facilitated our understanding of the interactions between the fluid phase and cell-bound components of the system. Structural and genetic analysis has shown that while many of these components are polymorphic, there are major similarities between many of the proteins serving enzymatic and regulatory roles in both the alternative and classical pathways. The regulation of complement activation and Class III genes, on chromosomes 1 and 6 respectively, encode nine of the major proteins in the system. The genetic basis of C4 and C3 polymorphisms is now well established, and further study may reveal functional differences between polymorphic variants of other components. The study of individuals with either genetic or acquired deficiencies of complement proteins and receptors has provided insight into the function of these components, leukocyte adherence deficiency (LAD) providing the best example. An appreciation of the genetics, structure and functions of the regulatory proteins decay-accelerating factor (DAF) and homologous restriction factor has enhanced our understanding of the pathogenesis of paroxysmal nocturnal haemoglobinuria. The full importance of CD59 glycoprotein, the newest member of the complement family, remains to be determined.

Periodontal disease mechanisms in immunocompromised patients

Deficiency in the number and function of phagocytes is associated with gingival inflammation and periodontitis. A hereditary deficiency in membrane glycoproteins involved in granulocyte adherence causes impaired chemotaxis, reduced phagocytosis and periodontal problems. Virus infections of antigen-presenting cells interfere with immune responses and lead to seriously increased susceptibility to infections with bacteria which cause no problems in normal patients. Increased levels of IgG antibodies may limit penetration of antigens in the tissues, but at the cost of local inflammation and tissue injury. Mucosal inflammatory disease with increased local formation of IgG is more frequent in IgA deficient patients. The immunological homeostasis depends on a balance between the respective classes and subclasses of antibodies. Deficiencies in the IgA system may contribute to a disturbed balance of the humoral immune response to critical antigens from oral bacteria. A disproportional increase in IgG1 and IgG3 antibodies may persistently activate complement, stimulate the inflammatory activity and cause tissue injury.

A 19-year-old man with leucocyte adhesion deficiency. In vitro and in vivo studies of leucocyte function

We describe a male patient with leucocyte adhesion molecule deficiency (LAD) of moderate phenotype. Although diagnosis was made only 2 years before his death, the patient survived until 19 years of age. This enabled us to perform a number of novel investigation, both in vivo and in vitro, relating to his leucocyte biology. Monocytes cultured in vitro matured into morphologically normal, phagocytically capable macrophages, which were able to recognize aged 'apoptotic' neutrophils. By injection of radiolabelled autologous neutrophils we demonstrated a prolonged neutrophil half-life, but normal margination, de-margination on exercise, and splenic pooling. Neutrophil adherence in vitro to vascular endothelium was normal. Histological examination of the patient's lungs at post-mortem showed intravascular aggregation of polymorphonuclear leucocytes but a paucity of cells in the interstitium and alveolar spaces. These findings indicate that the peripheral blood leucocytosis commonly observed in these patients may be due to prolonged intravascular neutrophil survival, and suggest that CD11/18 molecules have an important role in facilitating neutrophil emigration from blood vessels at sites of inflammation.

Bacteria-phagocyte interactions: emerging tactics in an ancient rivalry

Although phagocytes appear to have a redundancy of both oxidative and non-oxidative killing mechanisms, nevertheless, bacterial pathogens are still able to evade these defenses in vivo and cause lethal infection. As the mechanisms by which phagocytes function have become detailed at the molecular level, both the recognition of specific bacterial virulence determinants and their effects at specific sites in the phagocyte are also being identified. Knowledge of these interactions may permit the use of immunomodulators either to neutralize these virulence determinants or to enhance the bactericidal capabilities of the phagocyte.

The p67-phox cytosolic peptide of the respiratory burst oxidase from human neutrophils. Functional aspects

Most cases of cytosol-defective chronic granulomatous disease are due to the deficiency of a 47-kD protein (p47-phox) whose phosphorylation normally accompanies the activation of the respiratory burst oxidase. Recently, a form of chronic granulomatous disease was described in which the failure of O2- production was associated with the absence of a 67-kD polypeptide (p67-phox) from the cytosol of affected neutrophils. Using neutrophils obtained from a patient with this form of the disease, we examined the function of p67-phox in the activation of the oxidase. Our studies showed that in whole p67-phox-deficient neutrophils, p47-phox was phosphorylated in a normal fashion. In the cell-free oxidase-activating system, the ability of the p67-phox-deficient cytosol to support oxidase activation was partly restored by the addition of p47-phox-deficient cytosol; the p67-phox-deficient cytosol, however, was not complemented by cytosol inactivated with NADPH dialdehyde, an affinity label previously found to block the NADPH-binding component of the oxidase. Despite these differences, the kinetic properties of the p67-phox-deficient cytosol closely resembled those of the p47-phox-deficient cytosol. Taken together with earlier findings, these results suggest that (a) in the neutrophil cytosol, p67-phox is at least partly complexed to p47-phox; (b) it is in the form of this complex that p67-phox participates in oxidase activation; and (c) p47-phox appears to be translocated from the cytosol to the plasma membrane during oxidase activation, but complexation to p67-phox is not necessary for this translocation, nor for the accompanying extra protein phosphorylation.

Neutrophil function and oral disease

The pathological sequela of reduced neutrophil function in the oral cavity and the mechanisms behind dysfunction have added to our understanding of infectious diseases. Numerous examples have been given, and the overriding conclusion must be that any impairment of neutrophil function will lead to some degree of increased susceptibility to infection. Perhaps the tissue most sensitive to pathological changes in the oral cavity is the periodontium. In cases of severe neutrophil dysfunction, there is severe periodontal breakdown, but also in cases of "mild" neutrophil dysfunction, where there is no other infection, such as in individuals with LJP, there is severe periodontal breakdown. The molecular basis of neutrophil dysfunction is beginning to be understood in individuals with LJP, LAD, CGD, and AIDS. It is our hope that further research in this area will help to delineate the pathogenesis of these and other oral diseases.

Leukocyte adhesion molecules deficiency: its structural basis, pathophysiology and implications for modulating the inflammatory response

Understanding the molecular basis of a rare inherited disease, Leu-CAM deficiency in humans, has underscored the importance of the cellular component of inflammation and unravelled the complex series of homotypic and heterotypic cell interactions necessary for mobilization of leukocytes to infected sites. Furthermore, this disease has shown that several apparently distinct cellular inflammatory responses (e.g. aggregation, adhesion to endothelium, directed migration and phagocytosis) are mechanistically related and mediated by a set of molecules which belong to a larger group of adhesion molecules (Integrins) mediating similar phenomena critical for immune surveillance, lymphocyte homing, morphogenesis and thrombogenesis. This disease also showed the relative biologic importance of CD11/CD18 in leukocytes. CD11/CD18 are more critical for the functions of phagocytic cells as compared to lymphocytes although similar inhibitory effects of anti-CD11/CD18 mAbs can be demonstrated in vitro. Expression and function of CD11/CD18 is regulated at several levels which include formation of stable heterodimers, qualitative changes in the receptor and quantitative changes in the levels of expression of the receptors and their ligands. We have identified inherited single amino acid substitutions on CD18 which impair heterodimer formation and cell surface expression, thus accounting for the pathogenesis of Leu-CAM deficiency. We also found a stimulus-induced phosphorylation of CD18, which is transient in nature when elicited through other surface receptors. This may be important in regulation of CD11/CD18 receptor avidity, recycling, endocytosis and cross-talk with other receptors. Finally, realization of the profound impairment in the acute cellular inflammatory response present in Leu-CAM deficiency has permitted novel ways of controlling the inflammatory response in several situations were inflammation serves an injurious rather than a beneficial role to the host.

Pulmonary infection following exodontia in a patient with glycoprotein-180 deficiency

There is a significant increase in the occurrence and severity of infection in patients with immunodeficiencies, especially after minor invasive procedures. Therefore, alternatives to invasive procedures, continual vigilance of indwelling catheters, and appropriate preoperative evaluation and management of these patients are of paramount importance.

Activation of the NADPH oxidase in a cell-free system from human neutrophils stimulated by phorbol myristate acetate

Kinetics of activation of the NADPH oxidase in a fully soluble cell-free system from phorbol myristate acetate (PMA)-stimulated human neutrophils were investigated. In a cell-free system in which Mg2+ and sodium dodecyl sulfate, an anionic detergent required for the activation of NADPH oxidase are contained, cytosol prepared from PMA-stimulated neutrophils failed to activate PMA-stimulated neutrophil oxidase. However, cytosol prepared from resting (control) neutrophils was capable of activating PMA-stimulated neutrophil oxidase in a cell-free system in which its Km for NADPH was almost similar to that of control neutrophil oxidase. Cytosol from PMA-stimulated neutrophils could not activate control neutrophil oxidase, although it did not contain any inhibitors of NADPH oxidase activation. These results suggest that, in PMA-stimulated neutrophils, cytosolic activation factors may be consumed or exhausted, and that the affinity for NADPH of PMA-stimulated neutrophil oxidase may be the same as that of control neutrophil oxidase.

Adult respiratory distress syndrome

The Adult Respiratory Distress Syndrome (ARDS) is a fulminant form of respiratory failure affecting many seriously ill patients. The early manifestations of ARDS are caused by increased permeability of the alveolo-capillary barrier leading to pulmonary edema, stiff lungs, and a large right-to-left intrapulmonary shunt. Polymorphonuclear leukocytes (PMNS) are involved in the pathogenesis of most ARDS, and multiple PMN mechanisms can effect pulmonary injury; interactions between PMN adherence, proteolytic enzyme release, and oxygen radical production are emphasized. ARDS therapy remains largely supportive and has had little impact on mortality. The complications of infection and multiorgan failure play important roles in determining ARDS outcome.

Decreased adherence of polymorphonuclear neutrophils in children with viral infection

The adherence of polymorphonuclear neutrophils was examined in 16 children affected by enteritis, pneumonia, hepatitis and infectious mononucleosis. The results were compared with those obtained in 30 healthy adult volunteers and in 15 healthy children of the same age. Adhesiveness was significantly higher in adults than in healthy children, and significantly higher in healthy children than in children with viral infection. In 7 patients tested one month after regression of the disorder, PMN adhesiveness had returned to normal.

Cytokine-induced respiratory burst of human neutrophils: dependence on extracellular matrix proteins and CD11/CD18 integrins

Human polymorphonuclear leukocytes (PMN) released large quantities of hydrogen peroxide in response to tumor necrosis factor, but only when the cells were adherent to surfaces coated with extracellular matrix proteins. The PMN did not respond when exposed to cytokines and matrix proteins in suspension, or when exposed to cytokines while adherent to surfaces coated with stearic acid. PMN from children with genetic deficiency of the CD11/CD18 integrins underwent a normal respiratory burst upon adherence to uncoated polystyrene, but not in response to tumor necrosis factor when tested on polystyrene that was coated with serum, fibronectin, vitronectin, fibrinogen, thrombospondin, or laminin. Anti-CD18 antibodies, alone of sixteen antibodies tested, induced a similar defect in PMN from normal donors, when the PMN were tested on surfaces coated with serum, fibrinogen, thrombospondin, or laminin; no defect was induced by the anti-CD18 monoclonal antibody IB4 in normal PMN tested on surfaces coated with fibronectin or vitronectin. Thus, for cytokines to induce a respiratory burst in PMN, the cells must be able to use CD11/CD18 integrins and must interact with matrix proteins in the solid phase. CD11/CD18, which is already known to serve as a receptor for fibrinogen, may also be a receptor for thrombospondin and laminin. Finally, receptor(s) exist on PMN for fibronectin and vitronectin which are not blocked by the anti-CD18 antibody IB4 but which are nonetheless CD11/CD18 dependent.

History and implications of the neutrophil glycoprotein deficiencies

This review focuses on the initial clinical descriptions and subsequent investigation of the syndrome of recurrent infections associated with neutrophil membrane glycoprotein deficiencies. Characterization of the missing group of three glycoprotein heterodimers and their role in adhesion-related neutrophil function is summarized. Study of the clinical consequences of these genetically determined membrane glycoprotein defects has also contributed to the understanding of the role of normal neutrophils in both host defense and host tissue damage.

Characterization and cytoskeletal association of a major cell surface glycoprotein, GP 140, in human neutrophils

The binding of specific ligands to neutrophil cell surface receptors and the association of these receptors with the cytoskeleton may represent an essential step in activation. To identify surface proteins that are linked to the cytoskeleton during activation, neutrophil 125I-surface labeled plasma membranes were extracted with Triton X-100, and the soluble and insoluble (cytoskeleton) fractions analyzed by SDS-PAGE and autoradiography. The major cell surface proteins recruited to the cytoskeleton after activation with Con A, FMLP, zymosan-activated serum, or immune complexes possessed a relative molecular mass in the range of 80 to 13 kD. In addition to these proteins, WGA stimulates the recruitment of a 140-kD protein (GP 140) to the cytoskeletal fraction. That GP 140 is a WGA-binding protein was verified by Western blotting and WGA-Sepharose affinity chromatography. The Coomassie blue staining pattern of the WGA cytoskeletal fraction revealed major protein bands at apparent molecular weights of greater than 200 (approximately 250, 240, 235), 200, 115, 82/78 (a doublet), 56, 43, 36, and 18 kD. Labeling cells with 32PO4 before WGA treatment indicated that the cytoskeletal proteins with molecular weights of 115, 82/78, and 72 kD, and a 40-kD detergent soluble protein, are phosphorylated during activation. The 78 kD cytoskeletal phosphoprotein co-migrates with the lower subunit of erythrocyte (RBC) band 4.1 and shows strong cross-reactivity with RBC anti-band 4.1 antibody. Phosphorylation of cytoskeletal proteins like 4.1 may be involved in the regulation of interactions between GP 140 and the actin-containing cytoskeleton. Unlike the C3bi receptor, GP 140 is a major surface component of unactivated PMNs, has no stoichiometrically related 95-kD subunit, and has two isoforms with pIs in the range of 6.4 to 6.6. Under conditions that result in an increased expression of the C3bi receptor (such as treatment with the Ca2+ ionophore A23187), the amount of GP 140 on the PMN cell surface appears to be significantly reduced. The interaction of GP 140 with the cytoskeleton during activation suggests that GP 140 may play an important role in neutrophil functional responses.