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Biomedical subjects

S Sadallah

Publications and source records attributed to S Sadallah.

16 recordsLinked to original sources
PubMed2001

No complement receptor 1 stumps on podocytes in human glomerulopathies.

BACKGROUND: Type one complement receptor (CR1) is the only physiological inhibitor of complement on podocytes. CR1 is lost in different glomerulopathies, in particular in lupus nephritis, in which it has been suggested that CR1 is removed by proteolysis from the cell membrane. METHODS: To define whether proteolytic cleavage of CR1 on podocytes is a general phenomenon, we analyzed the expression of CR1 in different glomerulopathies using a monoclonal antibody against epitopes present on the extracellular portion of the molecule and a polyclonal antibody directed at the intracellular tail of CR1. The two antibodies were applied on sequential serial histologic sections of renal biopsy. RESULTS: In normal glomeruli, the two antibodies provided similar results, that is, strong staining of podocytes, and both were shown to recognize specifically CR1. Decreased expression of the extracellular portion of CR1 was observed in lupus nephritis (8/8), focal and segmental glomerulosclerosis (FSGS; 7/7), IgA nephritis (6/6), membranous glomerulonephritis (3/3), and minimal change disease (3/3). In each case, the decreased expression was accompanied by a simultaneous decrease of the expression of the intracellular tail of CR1 (Spearman's correlation coefficient rs = 0.951, P < 0.001). This observation was confirmed by analyzing focal glomerular lesions on sequential serial sections. CONCLUSION: These data indicate that there are no CR1 stumps on podocytes, even in lupus nephritis, and suggest that the CR1 loss on podocytes is not due to consumption but to decreased synthesis. A loss of CR1 synthesis might render podocytes highly sensitive to complement attack.

Antibodies, Monoclonal↗
PubMed2000

Induction of neutrophil responsiveness to myeloperoxidase antibodies by their exposure to supernatant of degranulated autologous neutrophils.

Antibodies against myeloperoxidase (MPO) and proteinase 3 (PR3) are the predominant autoantibodies present in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Their binding to the corresponding antigen on the surface of polymorphonuclear neutrophils (PMNs) is believed to trigger the disease process. Cytokines released during an inflammatory reaction are thought to prime resting PMNs, making them responsive to autoantibodies. In the present study we found that MPO but not PR3 could be detected on the cell surface of unstimulated PMNs after incubation with the supernatants of activated autologous PMNs. MPO was shown to be acquired from these supernatants, because PMNs did not express MPO when the supernatants were specifically MPO-depleted. In addition, purified soluble MPO bound to unstimulated PMNs. Unstimulated PMNs that had passively acquired MPO released oxygen radicals when incubated with monoclonal antibody anti-MPO or the immunoglobulin G fraction of a patient with MPO-ANCA. The data presented here suggest that, in ANCA-associated vasculitis, soluble MPO released by activated PMNs may bind to unstimulated PMNs, thereby making them reactive to anti-MPO antibodies. This mechanism of dispersing PMN activation would be specific for MPO-ANCA and may explain differences in the pathologic and clinical expression of MPO-ANCA versus PR3-ANCA vasculitis. (Blood. 2000;96:2822-2827)

Adsorption↗
PubMed2000

Interferon-alpha2a effects on complement activation and regulation in MS patients.

OBJECTIVES: To evaluate the treatment effect of recombinant interferon-alpha2a (rIFN-alpha2a) on complement activation and regulation in MS patients. MATERIAL AND METHODS: Plasma levels of the complement activation products C3bc and terminal complement complex (TCC) and serum levels of the complement regulatory proteins, complement receptor 1, CR1 (CD35) and the membrane inhibitor of reactive lysis, protectin (CD59), were determined by enzyme-linked immunosorbent assay (ELISA) in MS patients treated with IFN-alpha2a (14 patients) or placebo (7 patients). RESULTS: The level of soluble CD35 decreased while the level of TCC and to a lesser degree C3bc increased in the IFN-alpha2a treated patients during the initial part of the treatment. There was also a concomitant reduction of leukocytes in the same patients. CONCLUSIONS: The results indicate that complement is activated during the initial phase of rIFN-alpha2a treatment. This could partly be due to a concomitant reduction in soluble CD35.

Adult↗
PubMed1999

Ectosomes released by human neutrophils are specialized functional units.

Here we show that human polymorphonuclear leukocytes (PMN) release ectosomes independently of complement attack during their activation both in vitro and at the site of inflammation in vivo. Patterns of biotinylated proteins on the surface of PMN and on PMN-derived ectosomes indicated a specific sorting of cell surface proteins into and out of ectosomes. Ectosomes expressed clusters of complement receptor 1 (CR1), which allowed them to bind efficiently to opsonized bacteria. Myeloperoxidase and human leukocyte elastase, both stored within the azurophilic granules of PMN, were found to colocalize on ectosomes with CR1. Furthermore, myeloperoxidase colocalized with human leukocyte elastase. In contrast, not present on CR1-expressing ectosomes were CD63, a selective marker for the azurophilic granules, and CD14, which is located within the same granules and the secretory vesicles as CR1. Of the other complement regulatory proteins expressed by PMN, only CD59 colocalized with CR1, while CD55 and CD46 were almost absent. Ectosomes released by activated PMN at the site of inflammation may function as a well organized element (ecto-organelle), designed to focus antimicrobial activity onto opsonized surfaces.

Animals↗
PubMed1999

Complement receptor 1 (CD35) on human reticulocytes: normal expression in systemic lupus erythematosus and HIV-infected patients.

The low levels of complement receptor 1 (CR1) on erythrocytes in autoimmune diseases and AIDS may be due to accelerated loss in the circulation, or to a diminished expression of CR1 on the red cell lineage. Therefore, we analyzed the expression of CR1 on reticulocytes (R) vs erythrocytes (E). Healthy subjects had a significant higher CR1 number per cell on R (919 +/- 99 CR1/cell) than on E (279 +/- 30 CR1/cell, n = 23), which corresponded to a 3. 5- +/- 1.3-fold loss of CR1. This intravascular loss was confirmed by FACS analysis, which showed that all R expressed CR1, whereas a large fraction of E was negative. The systemic lupus erythematosus (SLE), HIV-infected, and cold hemolytic Ab disease (CHAD) patients had a CR1 number on R identical to the healthy subjects, contrasting with a lower CR1 on their E. The data indicated a significantly higher loss of CR1 in the three diseases, i.e., 7.0- +/- 3.8-, 6.1- +/- 2.9-, and 9.6- +/- 5.6-fold, respectively. The intravascular loss was best exemplified in a patient with factor I deficiency whose CR1 dropped from 520 CR1/R to 28 CR1/E, i.e., 18.6-fold loss. In one SLE patient and in the factor I-deficient patient, the FACS data were consistent with a loss of CR1 already on some R. In conclusion, CR1 is lost progressively from normal E during in vivo aging so that old E are almost devoid of CR1. The low CR1 of RBC in autoimmune diseases and HIV-infection is due to a loss occurring in the circulation by an active process that remains to be defined.

Agglutinins↗
PubMed1999

Elastase and metalloproteinase activities regulate soluble complement receptor 1 release.

Complement receptor 1 (CR1) is cleaved from the surface of polymorphonuclear cells (PMN) in the membrane-proximal region to yield a soluble fragment (sCR1) that contains the functional domains. The enzymes involved in this cleavage are produced by the PMN itself, since in vitro stimulation of purified PMN is followed by sCR1 release. Purified human neutrophil elastase (HNE) cleaved CR1 from erythrocytes and urinary vesicles originating from podocytes and enhanced tenfold the cleavage of CR1 from activated PMN. The largest fragment released from PMN by HNE was identical in size to CR1 shed spontaneously. The CR1 fragments cleaved from erythrocytes were functional. The shedding of sCR1 by activated PMN was inhibited by phenylmethylsulfonyl fluoride (80 +/- 10%), alpha1-antiprotease (50 +/- 5%) and elafin (60 +/- 5%). Furthermore the cleavage was blocked by the metalloprotease inhibitor 1,10-phenanthroline (70 +/- 6 %) as well as by a monoclonal antibody against human neutrophil collagenase MMP8 (40 +/- 10%). Maximal inhibition of sCR1 shedding was obtained by a combination of 1,10-phenanthroline with elafin (86 +/- 6%). These inhibitors had no effect on L-selectin shedding, indicating that the cleavage of CR1 was specific. In conclusion, elastase or elastase-like activity may be responsible for the shedding of functional sCR1 in vivo, and this activity is controlled by the local release of PMN metalloproteases and alpha1antiprotease.

Complement C3b↗
PubMed1999

Soluble complement receptor 1 is increased in patients with leukemia and after administration of granulocyte colony-stimulating factor.

Complement receptor type 1 is expressed by erythrocytes and most leukocytes. A soluble form is shed from the leukocytes and found in plasma (sCR1). sCR1 is a powerful inhibitor of complement. We report an increased sCR1 in the plasma of leukemia patients, up to levels producing measurable complement inhibition. Half of the 180 patients with acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic lymphocytic leukemia (CLL) had sCR1 levels above the normal range. The highest levels were observed in T-ALL (17 patients). The complement function of a T-ALL serum was improved by blocking sCR1 with a specific mAb (3D9). Measurements in 16 peripheral stein cell donors before and after granulocyte colony-stimulating factor (G-CSF) administration showed an increase in sCR1 (before, 43.8+/-15.4; at day 5, 118.3+/-44.7 ng/mL; P < 0.0001). This increase paralleled the increase in total leukocyte counts and was concomitant with de novo leukocyte mRNA CR1 expression in all three individuals tested. Whether pharmacological intervention may be used to up-regulate sCR1 so as to inhibit complement in vivo should be further investigated.

Animals↗
PubMed1999

Glomerulonephritis in a patient with complement factor I deficiency.

Complement factor I deficiency is known to be associated with recurrent pyogenic infections. The patient described here had recurrent attacks of otitis, sinusitis, and bronchopneumonia since childhood. At the age of 24 years, he had an acute episode of systemic vasculitis with purpura, but no nephritis. A factor I deficiency was diagnosed when he was 36 years old. Because of the uncontrolled activation of the alternative pathway of complement, several other components were depleted, in particular C3, which explained the predisposition for pyogenic infections. A progressive loss of renal function accompanied by proteinuria and hematuria started after the age of 40 years. Renal biopsy showed a focal segmental glomerulonephritis (GN) with glomerular deposits of immunoglobulins and complement C3 and C4 fragments. The glomerular podocytes showed an almost complete loss of complement receptor 1 (CR1; CD35). The expression of CR1 was very low on erythrocytes, as well. Thus, CR1, the most efficient cell-bound cofactor for the inactivation of C4b/C3b by factor I, appears to be consumed when factor I is missing. Although this is the first report of factor I deficiency associated with GN, it is unlikely that the development of the nephritis was fortuitous because GN has been found in many other diseases characterized by uncontrolled activation of the alternative pathway.

Adult↗
PubMed1999

High incidence of transiently appearing complement-sensitive bone marrow precursor cells in patients with severe aplastic anemia--A possible role of high endogenous IL-2 in their suppression.

In a prospective long-term study on the incidence of paroxysmal nocturnal hemoglobinuria (PNH), 115 consecutive patients with severe aplastic anemia (SAA), 97 treated with antilymphocyte globulin (ALG) and 18 with bone marrow transplantation (BMT), were observed over a period of 4-18 years and tested for the presence of complement-sensitive hematopoietic precursor cells with the bone marrow (BM) sucrose test. Sixteen (14%) of the ALG-treated patients developed clinical signs of PNH between 0.5 and 8 years after treatment. Complement-sensitive BM precursors were found in 89% of the SAA patients at some time during their disease, but in none of 18 normal donors. At diagnosis, their proportion was significantly higher in patients who later developed PNH than in patients who later achieved disease-free complete remission (CR). After ALG, the abnormal population was found in both groups, but it was gradually replaced by normal precursors in remission patients. After BMT, the complement-sensitive population decreased to very low numbers in patients with a stable graft, but increased again in 3 patients upon graft rejection. Mimicking the PNH defect by enzymatic removal of glycosyl-phosphatidylinositol (GPI)-linked proteins from CD34+ cells resulted in their complement sensitivity, suggesting that the BM sucrose test identifies precursor cells carrying the PNH defect. In 66 patients, white blood cells (WBC) in peripheral blood (PB) were examined for GPI-deficient populations by flow cytometry (FACS). Ten patients with signs of clinical or laboratory PNH had over 25% complement-sensitive precursor cells in the BM and a GPI-deficient WBC population in the PB. Of 56 SAA patients without PNH, 8 had an abnormal population detectable with both tests, 26 only with the BM sucrose test, 4 only with PB FACS analysis, and in 18, no abnormal cells were detected with either test. In search for parameters which might explain why in some patients the abnormal population expands, while it regresses or disappears in others, we tested the release of IL-2 as a parameter of immune competence. At diagnosis, IL-2 release was approximately 50% of normal in patients who later developed PNH, while it was double the normal value in patients who later achieved CR. We conclude that the majority of SAA patients transiently harbor complement-sensitive precursor cells in the BM. Patients with more than 25% abnormal BM precursors and low endogenous IL-2 release are at risk of progression to clinical PNH.

Anemia, Aplastic↗
PubMed1998

Reference typing report for complement receptor 1 (CR1).

A total of 100 Chinese blood donors (50 from Shen-Zhen and 50 from Taiwan) were studied by the participants in addition to 9 reference samples. A new nomenclature for the CR1 structural alleles was recommended by the participants which would use a numbering system, e.g. CR1*1. The structural allele frequencies in the Chinese were: CR1*1 (190 kD) 0.96, CR1*2 (220 kD) 0.03, CR1*3 (160 kD) 0.01 and CR1*4 (250 kD) 0.00. The HindIII expression polymorphism was also studied and the high expressing allele had a gene frequency of 0.71 while the low expressor gene frequency was 0.28. Erythrocyte copy numbers were quantified and compared between laboratories with good correlation (R = 0.55-0.88). The mean (+/- SD) erythrocyte copy number was 463 (+/- 229) in the Taiwan donors and 446 (+/- 207) in the Mainland Chinese.

Alleles↗
PubMed1998

Soluble complement receptor type 1 (CD35) in bronchoalveolar lavage of inflammatory lung diseases.

Complement receptor type 1 (CR1) (CD35; C3b/C4b receptor) is a transmembrane protein of many haematopoietic cells. Once cleaved, soluble complement receptor type 1 (sCR1) exerts opposite effects as a powerful inhibitor of complement. This study addressed both the question of whether sCR1 was found in bronchoalveolar lavage (BAL) of normals and patients with various inflammatory disease, and its possible origin. In this retrospective study covering specimen and clinical data of 124 patients with acute and chronic inflammatory lung pathologies, BAL supernatants were analysed by enzyme-linked immunosorbent assay technique for sCR1. Correlations were made between the sCR1 levels obtained and the constituents of BAL. Human alveolar macrophages were cultivated in order to determine their secretory capacity of sCR1. Alveolar macrophages from normal subjects were shown to release sCR1 in vitro. In addition, sCR1 was present in BAL of normal controls and was significantly increased in acute inflammatory lung diseases such as acute respiratory distress syndrome (ARDS), bacterial and Pneumocystis carinii pneumonia, as well as in chronic inflammatory diseases such as interstitial lung fibrosis and sarcoidosis. In BAL of ARDS, bacterial, and P. carinii pneumonia, there was a good correlation between sCR1 and the absolute neutrophil counts. In sarcoidosis, a correlation was found with BAL lymphocyte counts. Serum sCR1 was not increased in patients compared to controls. Soluble complement receptor type 1 (sCR1) is found in the bronchoalveolar lavage in health as well as in acute and chronic inflammatory disease. Alveolar macrophages are capable of releasing sCR1 in vitro and may be the main physiological source of sCR1 in the alveoli. The good correlation between sCR1 and the absolute neutrophil or lymphocyte numbers in bronchoalveolar lavage of inflammatory diseases suggests a predominant role of leucocytes for the release of sCR1 in such conditions. The release of this inhibitor of complement may be crucial to control and reduce complement activation and thus prevent lung injury.

Bronchoalveolar Lavage Fluid↗
PubMed1997

CR1, CD35 in synovial fluid from patients with inflammatory joint diseases.

OBJECTIVE: To investigate synovial fluid (SF) for the presence of CR1 and to study its relationship to SF leukocytes and to serum levels of soluble CR1 (sCR1) in patients with rheumatic diseases. METHODS: Synovial fluids were collected from 35 patients with rheumatoid arthritis (RA) and 26 patients with other inflammatory joint diseases. Total CR1 in the SF and serum were measured with a sandwich enzyme-linked immunosorbent assay (ELISA) that recognized both soluble and transmembrane forms of CR1. The characteristics of CR1 in SF were analyzed by ultracentrifugation and by a second ELISA specific for transmembrane CR1. RESULTS: CR1 was found in all SF samples tested (range 5-281 ng/ml). SF CR1 was higher in patients with RA (mean +/- SD 81 +/- 66 ng/ml) than in those with other inflammatory joint diseases (31.8 +/- 23.8 ng/ml) (P < 0.001). Serum sCR1 was not significantly increased in the patients compared with the normal subjects. There was no correlation between serum sCR1 and SF CR1. In 44% of the patients, the SF CR1 level was higher than the serum sCR1 level. A fraction (30-80%) of SF CR1 was pelleted by ultracentrifugation and, unlike serum sCR1, it reacted in an ELISA specific for transmembrane CR1. Thus, SF contained 2 forms of CR1: a membrane-associated and a soluble form, which was confirmed by sucrose density-gradient ultracentrifugation. SF CR1 levels correlated directly with the number of SF total leukocytes and polymorphonuclear leukocytes (PMN). These 2 forms of CR1 were also found in the supernatant of in vitro-activated PMN from normal subjects. SF CR1 exhibited the capacity to act as a cofactor for the factor I degradation of C3b. CONCLUSION: CR1 is found in the SF of patients with joint inflammation. The data suggest that SF CR1 originates from the infiltrating leukocytes, which shed both a soluble and a membrane-associated form. Whether SF CR1 participates in the local regulation of complement activation remains to be examined.

Arthritis↗
PubMed1996

Increased levels of soluble complement receptor 1 in serum patients with liver diseases.

Complement receptor type 1 (CR1) is an integral membrane protein of many hematopoietic cells and is found in a soluble form in plasma. Preliminary data have indicated that soluble complement receptor 1 (sCR1) levels in serum were increased in patients with cirrhosis. In this study, sCR1 was measured in patients with various liver diseases with a newly established enzyme-linked immunosorbent assay (ELISA). sCR1 level was elevated in chronic active hepatitis C (24 patients, 62.6 +/- 31 ng/ML; 31 normal controls, 31.4 +/- 7.8 ng/mL, P < .001), and in cirrhosis (35 patients, 143.7 +/- 61 ng/mL, P < .001). The levels increased transiently in 3 patients who had amanita phalloides intoxication. In 25 patients with advanced cirrhosis (pretransplantation screening), there were significant inverse correlations between sCR1 and both the prothrombin index (rs = -.60, P < .002) and the aminopyrine breath test (rs = -.51, P < .01). Following liver transplantation, the levels dropped from 166 +/- 70 to 49 +/- 24 ng/mL (P < .0001), and serial measurements in the posttransplantation period showed a correlation with liver dysfunction, regardless of etiology. Since CR1 is not produced by hepatocytes, the most likely explanation for the increased level of sCR1 is reduced is reduced catabolism. Thus, sCR1 may be added to the short list of large glycoproteins that accumulate in liver disease.

Amanita↗
PubMed1996

Soluble complement receptor type 1 in serum and cerebrospinal fluid of patients with Guillain-Barré syndrome and multiple sclerosis.

Activation of complement is critically involved in inflammatory reactions in both Guillain-Barré syndrome (GBS) and multiple sclerosis (MS). Soluble human complement receptor 1 (sCR1) blocks complement activation by both classical and alternative pathways. We studied serum and cerebrospinal fluid (CSF) concentrations of sCR1 in 23 patients with GBS, 27 patients with MS and 30 controls. No significant differences were found between patients and controls. Transient liver affection probably caused high serum sCR1 levels in two patients with GBS. The serum and CSF sCR1 levels were not correlated to the disease activity of GBS and MS, nor to the relapsing-remitting or chronic-progressive forms of MS. In GBS the CSF sCR1 levels correlated with the CSF total protein concentrations (r = 0.9, P < 0.01), suggesting that sCR1 leaks from serum into CSF via a damaged blood-nerve barrier. The serum sCR1 levels in GBS were slightly higher than in MS (P < 0.05). Whether this reflects changes in the release or consumption of sCR1 in these patients is at present unknown.

Adult↗
PubMed1994

Identification of membrane-bound CR1 (CD35) in human urine: evidence for its release by glomerular podocytes.

Complement receptor 1 (CR1) is present on erythrocytes (E-CR1), various leucocytes, and renal glomerular epithelial cells (podocytes). In addition, plasma contains a soluble form of CR1 (sCR1). By using a specific ELISA, CR1 was detected in the urine (uCR1) of normal individuals (excretion rate in 12 subjects, 3.12 +/- 1.15 micrograms/24 h). Contrary to sCR1, uCR1 was pelleted by centrifugation at 200,000 g for 60 min. Analysis by sucrose density gradient ultracentrifugation showed that uCR1 was sedimenting in fractions larger than 19 S, whereas sCR1 was found as expected in fractions smaller than 19 S. The addition of detergents reduced the apparent size of uCR1 to that of sCR1. After gel filtration on Sephacryl-300 of normal urine, the fractions containing uCR1 were found to be enriched in cholesterol and phospholipids. The membrane-association of uCR1 was demonstrated by analyzing immunoaffinity purified uCR1 by electron microscopy which revealed membrane-bound vesicles. The apparent molecular mass of uCR1 was 15 kD larger than E-CR1 and sCR1 when assessed by SDS-PAGE and immunoblotting. This difference in size could not be explained on the basis of glycosylation only, since pretreatment with N-glycosidase F reduced the size of all forms of CR1; however, the difference in regular molecular mass was not abrogated. The structural alleles described for E-CR1 were also found for uCR1. The urine of patients who had undergone renal transplantation contained alleles of uCR1 which were discordant with E-CR1 in 7 of 11 individuals, indicating that uCR1 originated from the kidney. uCR1 was shown to bind C3b-coated immune complexes, suggesting that the function of CR1 was not destroyed in urine. A decrease in uCR1 excretion was observed in 3 of 10 patients with systemic lupus erythematosus, corresponding to the three who had severe proliferative nephritis, and in three of three patients with focal sclerosis, but not in six other patients with proteinuria. Taken together, these data suggest that glomerular podocytes release CR1-coated vesicles into the urine. The function of this release remains to be defined, but it may be used as a marker for podocyte injury.

Adult↗