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Biomedical subjects

P Densen

Publications and source records attributed to P Densen.

At least 55 records · Page 3Linked to original sources
PubMed1987

Killing of Neisseria meningitidis by human neutrophils: implications for normal and complement-deficient individuals.

The contributions of complement-dependent phagocytosis and serum bactericidal activity (SBA) to the killing of 62 strains of meningococci were examined by using C8-depleted or pooled human serum (PHS). The complement-dependent nature of killing by neutrophils was confirmed by restoring survival to control values by using heated serum. Serogroups B and 29E, but not A, C, Y, and W135, were ingested and killed by neutrophils in C8-depleted PHS (PHS-C8Dep; 41.7% +/- 7.3% and 60.5% +/- 17.8% vs. greater than or equal to 100% survival, respectively, at 30 min). Group B meningococci were resistant to complement-mediated SBA, whereas group Y were susceptible. Deposition of C3 on serogroups B and Y was similar (28.5 +/- 2.9 vs. 23.5 +/- 2.7 C3 fluorescence units; P greater than .05); however, susceptibility to complement-dependent phagocytosis and complement-mediated SBA of serogroups B and Y did not correlate. We also examined meningococcal phagocytosis by using serum from a C8-deficient patient. In contrast to PHS-C8Dep, this serum supported rapid phagocytic killing of serogroups A, C, Y, and W135 meningococci. This finding suggests that vaccinating individuals deficient in late-complement components may shift the burden of host defense from SBA to phagocytosis.

Blood Bactericidal Activity↗
PubMed1987

Specificity of antibodies against Neisseria gonorrhoeae that stimulate neutrophil chemotaxis. Role of antibodies directed against lipooligosaccharides.

Five strains each of Neisseria gonorrhoeae sensitive or resistant to complement (C) dependent killing by normal human serum (NHS) were examined for their ability to stimulate chemotaxis of polymorphonuclear leukocytes (PMNs) after preincubation with NHS; or IgM or IgG derived from NHS. Serum-sensitive N. gonorrhoeae stimulated C-dependent chemotaxis when opsonized with IgM, but not IgG, however, serum-resistant strains, taken as a whole, failed to promote chemotaxis when opsonized with either isotype. IgM titers in NHS against lipooligosaccharide (LOS) antigens from individual serum-sensitive, but not serum-resistant strains, correlated with the magnitude of chemotaxis generated by the corresponding opsonized strains (r = 0.99). Western blots demonstrated that IgM and IgG from NHS recognized different antigenic determinants on LOS from serum-sensitive gonococci. IgM from NHS immunopurified against serum-sensitive LOS accounted for two-thirds of the chemotaxis promoting activity present in whole serum. IgG titers in NHS against LOS antigens from individual serum-resistant strains also correlated with magnitude of chemotaxis generated by the corresponding opsonized strains (r = 0.87), although most opsonized serum-resistant strains did not generate significantly higher magnitudes of chemotaxis than controls. In contrast, a serum-resistant isolate from a patient with disseminated gonococcal infection (DGI) stimulated chemotaxis when opsonized with IgG obtained from the patient's convalescent serum. By Western blot, convalescent IgG antibody recognized an additional determinant on serum-resistant LOS not seen by normal IgG.

Adult↗
PubMed1986

Functional C8 associated with human platelets.

Haemolytic assay for C8 revealed its association in functionally active form with washed human platelets. Platelet-bound C8 haemolytic activity was inhibited by F(ab')2 anti-C8 and was undetectable in the platelet suspension obtained from three C8 deficient patients. Incubation of platelets from C8 deficient individuals in normal plasma did not restore C8 haemolytic activity, indicating that platelets do not absorb C8 from plasma in vitro during platelet preparation. Thrombin, a mediator of the platelet release reaction, did not induce the release of C8 from normal platelets. Conversely, lysis of EAC1-7.9 by platelet bound C8 was not accompanied by release of beta-thromboglobulin or serotonin from the platelets. C8 was detected in a homogenate prepared from platelets as well as in the supernatant collected after high speed centrifugation of the homogenate. The association of C8 with platelets as an individual component rather than as part of the C5b-9 membrane-attack complex was supported by the following evidence: platelet bound C8 eluted from a Sephacryl S-200 column at the same volume as C8 from normal human serum; F(ab')2 anti-C8, but not F(ab')2 anti-C5, inhibited platelet C8 activity; the platelet homogenate, which lysed EAC1-7.9, had no effect on EAC43 which are susceptible to the lytic activity of the C5b-9 complex.

Blood Platelets↗
PubMed1985

Group G streptococcal bacteremia. The clinical experience at Boston University Medical Center and a critical review of the literature.

Twenty-six patients with bacteremia caused by group G streptococci were seen during a 29-month period. Our findings suggest that the epidemiology of these infections has not changed appreciably during the last 15 years. The disease occurs most commonly as an acute community-acquired infection in older persons with underlying conditions predisposing to skin breakdown. Patients with these bacteremias fall into three categories: those with associated cutaneous infection only; those with serious focal infection; and those with probable infection. Underlying neoplastic conditions were relatively uncommon (25%) in our series compared with others (65%). In contrast to recent reports emphasizing this complication, endocarditis was uncommon in our patients. A prompt response to therapy with beta-lactam antibiotics occurred in most of our patients.

Adult↗
PubMed1985

Opsonophagocytosis of Neisseria gonorrhoeae: interaction of local and disseminated isolates with complement and neutrophils.

The phagocytosis of serum-sensitive (SS) and serum-resistant (SR) gonococci by neutrophils was examined. SS strains were more rapidly and completely ingested and killed than were SR strains (8.8% +/- 3.4% vs. 64.4% +/- 7.7% survival at 30 min [P less than .005]) in C8-deficient serum or C8-depleted normal serum. Opsonic requirements of the two types of isolates differed. Heat-labile and -stable serum factors played an important role in the phagocytosis of SS but not SR strains. Indeed, killing of SR strains by polymorphonuclear neutrophils did not vary over a 1,000-fold change in serum concentration. SS strains consumed and fixed C3 more rapidly and in greater amounts than did SR strains (83.3% +/- 17.4% vs. 20.8% +/- 5.0% at 10 min [P less than .01]). However, this difference in C3 consumption and fixation did not completely account for the difference in phagocytosis because killing of SS strains was still greater than that of SR strains under conditions of equal C3 fixation.

Blood Bactericidal Activity↗
PubMed1984

Antineutrophil antibodies in infectious mononucleosis.

Antineutrophil antibodies were detected in the serum of 12 of 14 patients with acute Epstein-Barr virus-induced infectious mononucleosis. These antibodies were present in two patients with mononucleosis and severe neutropenia, and in 10 patients with mononucleosis uncomplicated by severe neutropenia. Antineutrophil antibodies were not detected in serum from five patients with cytomegalovirus-induced mononucleosis, or five renal allograft recipients with primary or reactivation Epstein-Barr virus infection. This study suggests that antineutrophil antibodies are among those produced by the polyclonal activation induced by Epstein-Barr virus during acute infectious mononucleosis.

Adult↗
PubMed1984

Complement deficiency states and infection: epidemiology, pathogenesis and consequences of neisserial and other infections in an immune deficiency.

Inherited deficiencies of the complement proteins are rare in unselected populations. Examination of patients with the clinical correlates of complement deficiency (autoimmune disease and certain bacterial infections) shows the frequency of inherited complement deficiency to rise enormously (5.9% of patients with systemic lupus erythematosus, 10 to 25% of adults with sporadic meningococcal disease). Autoimmune diseases of all types, but especially systemic lupus erythematosus, discoid lupus and glomerulonephritis, are seen in all categories of complement deficiency, most typically in those of the early classical pathway (C1, C4, C2). Pneumococcal infections are characteristic of deficiencies of the early classical pathway, as well. Deficiencies of C3 are associated with severe disease including autoimmune phenomena, pneumococcal and neisserial infections. C3-deficient patients become ill substantially earlier in life. Infections with N. meningitidis and N. gonorrhoeae are most typical of the late component deficiencies, with over 40% of homozygotes affected. Despite the presence of this deficiency from birth and the peak age-specific incidence of meningococcal disease in the general population at ages 3-8 months, the median age of first infection in the late component-deficient patients is 17 years. Relapse of infection is ten times more common in these patients, and discrete recurrences are seen in 45% of affected individuals. An unusual and unexplained predilection for infection with serogroup Y N. meningitidis exists. Despite an immune deficiency, and problems with ascertainment bias, it appears that persons with late component complement deficiency enjoy less mortality than normals who contract meningococcal disease. Attempts to explain the pathogenesis of neisserial infection in late component deficiencies have focused on the concept that normally non-pathogenic serum-sensitive bacteria are etiologic in the absence of serum bactericidal activity. Data to support this concept remain to be developed and contrary data exist. A separate mechanism may predispose properdin-deficient patients to meningococcal infection, since they appear to develop fulminant infections with high mortality.

Adolescent↗
PubMed1983

Inherited deficiency of C8 in a patient with recurrent meningococcal infections: further evidence for a dysfunctional C8 molecule and nonlinkage to the HLA system.

An adult male with recurrent meningococcal infections is reported whose serum lacked functional C8 activity but possessed antigenic C8. The addition of 1500 U of purified C8/ml of serum restored hemolytic activity to normal. Four to five times more C8 was required to restore bactericidal activity than to restore hemolytic activity. Bactericidal activity could also be restored by mixing the patient's serum with a second C8-deficient serum that lacked detectable antigenic or functional C8. The patient's serum contained bactericidal antibody for groups A, B, C, and Y meningococci and specific antibody to group Y capsular polysaccharide. There was two to three times more bactericidal antibody activity in the serum than in a pool of normal sera for the infecting strain. Family studies disclosed a sibling who was HLA identical to the patient but whose serum contained normal amounts of total hemolytic and C8 functional activity.

Adolescent↗
PubMed1983

Beta chain deficiency in three patients with dysfunctional C8 molecules.

Structural and functional studies were performed on a dysfunctional C8 molecule present in the serum of two siblings and an unrelated individual. The C8 in these three sera exhibited a pattern of partial immunologic identity with C8 in normal serum but was devoid of functional activity. The C8 was immunoprecipitated from the three sera and from a control serum with an antihuman C8 antiserum and analyzed by SDS-PAGE using highly purified human C8 as a reference. A selective absence of a band of 62,000 mol. wt was observed in the immunoprecipitates from the sera containing dysfunctional C8. Experiments performed with the purified alpha-gamma and beta subunits showed that the hemolytic activity of the C8 deficient sera could be reconstituted by the addition of the beta chain but not the alpha-gamma dimer. Binding of the dysfunctional C8 to C567 was excluded by the following observations: (1) EAC1-7 treated with the C8 deficient sera and then washed could not be lysed after the addition of the beta subunit and C9; and (2) the abnormal molecules did not interfere with the consumption of normal C8 by the soluble complex SC5b-7.

Binding, Competitive↗
PubMed1983

Two types of dysfunctional eighth component of complement (C8) molecules in C8 deficiency in man. Reconstitution of normal C8 from the mixture of two abnormal C8 molecules.

Restoration of hemolytic activity was examined in sera from seven unrelated eighth component of complement (C8)-deficient subjects. The sera fell into two groups, depending on whether hemolytic activity was restored by the addition of the beta-chain (group 1) or the alpha-gamma-subunit (group 2) purified from normal human C8. Antigenic analysis of these sera by double-immunodiffusion using anti-human C8 confirmed previous findings of a dysfunctional C8 in the four sera of group 1 and established the presence of a different dysfunctional C8 in one of the sera of group 2 when tested at a high concentration. Further characterization of the dysfunctional C8 molecules in the two sera by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that group 1 sera were missing the beta-subunit and group 2 sera were missing the alpha-gamma-subunit of the C8 molecule. Sera from either of these two groups alone did not produce hemolysis in hemolytic plates containing sheep erythrocytes coated with antibody and complement components up to C7 (EAC1-7) and C9. When sera from the two groups were added to adjacent wells in the hemolytic plates, a zone of hemolysis developed between the wells. The contribution of C8 alpha-gamma from the sera of group 1 and of C8 beta from those of group 2 to the lysis of EAC1-7 in the presence of C9 was confirmed by the inhibitory effect of specific antibodies against the two C8 subunits. In experiments in which hemolytic activity was reconstituted by mixing sera from group 1 with sera from group 2, the serum source of C8 beta (group 2) was the limiting reagent. The dysfunctional C8 molecule in this serum was able to bind to EAC1-7. Chromatographic analysis demonstrated that the generation of hemolytic activity in the mixture of the two sera resulted from the reconstitution of the C8 molecule rather than the sequential action of the two C8 subunits.

Antibody Formation↗
PubMed1982

Dissemination of gonococcal infection is associated with delayed stimulation of complement-dependent neutrophil chemotaxis in vitro.

Gonococci isolated from patients with uncomplicated gonorrhea or disseminated infection were examined for their ability to stimulate neutrophil chemotaxis in vitro. A neutrophil chemotactic response was not observed when as many as 10(9) colony-forming units of gonococci were incubated in buffer alone. However, a striking response was observed when 4 x 10(7) colony-forming units were incubated in 10% pooled normal human serum. Activation of complement was required for chemotaxis as demonstrated by complement consumption and failure of chemotactic activity generation in serum treated with heat or EDTA. Chromatography of activated serum demonstrated a single peak of chemotactic activity with an apparent molecular weight of 15,000 and was shown to be due to C5a. Examination of the kinetics of chemotactic factor generation demonstrated that local isolates stimulated a rapid response (about 60% maximal in 5 min), whereas the response to disseminated isolates was delayed (50% maximal in 20 to 30 min). Chemotactic activity generated by both types of isolates was suppressed at early time periods in agammaglobulinemic serum, indicating that immunoglobulins contribute to the generation of activity. Both pathways of complement activation were utilized by the two types of gonococci, but there was preferential dependence on the alternative pathway for disseminated strains and on the classical pathway for local isolates. We suggest that delayed stimulation of complement-dependent neutrophil migration may account in part for the infrequency of genital symptoms and may contribute to the mechanism of dissemination in patients with systemic gonococcal infection.

Chemotaxis, Leukocyte↗
PubMed1981

Diminished neutrophil oxidative metabolism after phagocytosis of virulent Salmonella typhi.

The interactions of human polymorphonuclear neutrophils (PMNs) with virulent and avirulent strains of Salmonella typhi were examined. Ingestion of the S. typhi strains by PMNs was evaluated with three techniques: visual examination of PMN monolayers (phagocytic index); uptake of radiolabeled S. typhi by PMNs; and removal of S. typhi from the supernatant of suspensions of PMNs and bacteria. All three techniques indicated equivalent phagocytosis of the strains. Postphagocytic PMN oxidative metabolism was quantitated with measurements of oxygen consumption, protein iodination, and chemiluminescence. We found that although PMNs ingested equal numbers of virulent and avirulent S. typhi, those PMNs ingesting the virulent organisms exhibited a significantly smaller increase in postphagocytic oxidative metabolism than PMNs ingesting avirulent S. typhi. Despite this muted oxidative burst the virulent bacteria were killed as well as the avirulent strains. Virulent S. typhi either fail to stimulate receptors that trigger PMN oxidative metabolism or inhibit PMN oxidative metabolism. Our data support the former hypothesis.

Blood Bactericidal Activity↗
PubMed1981

Kx: its relationship to chronic granulomatous disease and genetic linkage with Xg.

The relationship between neutrophil function and the neutrophil antigen, Kx, as well as the linkage of the gene, Xk, with Xg was examined in a kindred with X-linked chronic granulomatous disease. Four of the eight male siblings had chronic granulomatous disease by clinical history and tests of neutrophil function, and all four had Kx-negative neutrophils. The remaining four were in good health and had normal nitroblue tetrazolium reduction tests. However, one of these latter four had Kx-negative neutrophils that functioned normally. These data suggest that closely linked but distinct genes on the X chromosome code for chronic granulomatous disease and Kx. In addition, close linkage was demonstrated between Xk and Xg, a gene coding for an erythrocyte surface antigen.

Adult↗
PubMed1978

Gonococcal interactions with polymorphonuclear neutrophils: importance of the phagosome for bactericidal activity.

Gonococci are capable of attaching to the surface of polymorphonuclear leukocytes (PMN). In this location they resist phagocytosis and are not killed by PMN. To delineate the factors involved in the survival of these gonococci, we investigated the interaction of virulent gonococci, which adhere to cells and resist phagocytosis, and avirulent gonococci, which are phagocytized and killed by PMN. In the presence of serum, both virulent and avirulent gonococci associate equally well with PMN and stimulate increases in oxidative metabolism. In the absence of serum virulent gonococci attached to PMN and stimulated PMN oxidative metabolism to a greater extent than avirulent gonococci which did not attach to PMN (P = 0.0009). Therefore, the survival of virulent gonococci attached to the PMN surface is not a result of failure to activate oxidative and bactericidal mechanisms. Both virulent and avirulent gonococci stimulated equivalent PMN specific granule release as measured by the appearance of lactoferrin in the media. Phagocytosis of avirulent gonococci stimulated significantly greater beta-glucuronidase release (P = 0.01) and myeloperoxidase-mediated iodination of protein (P = 0.001) by PMN than attachment of virulent gonococci. In the absence of serum neither type of gonococci stimulated beta-glocuronidase release or protein iodination by PMN. Thus, virulent gonococci fail to stimulate primary granule release by PMN. To further assess the role of attachment versus ingestion on the survival of gonococci, PMN were treated with cytochalasin B to block ingestion. Cytochalasin B-treated PMN were unable to kill either virulent or avirulent gonococci despite normal degranulation stimulated by the latter. The failure of PMN to kill surface-attached gonococci appears to be a consequence of the failure of PMN to enclose the virulent gonococci within a phagosome. The phagocytic vacuole thus plays a critical role in normal PMN bactericidal activity by providing a closed space in which the proper concentration of substances may be achieved to generate microbicidal activity.

Blood Bactericidal Activity↗