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PubMed1984

Fc and complement receptor integrity of polymorphonuclear (PMN) cells following thermal injury.

In patients sustaining thermal injury, a sequential study was formulated to evaluate Fc and complement receptor expression of polymorphonuclear cells (PMN). Additionally, the role of factors in burn sera and maturity of PMN cells in the circulation were studied. The salient features of the study were: Marked reduction in Fc receptor expression by the 5th day of injury in both survivors and non-survivors. Thereafter levels gradually increased in survivors, though they were still below the normal range. In non-survivors, the depression was severe and persistent. In contrast to Fc receptor expression, complement receptor integrity was not grossly affected in both survivors and non-survivors. Burn sera collected from survivors on the 5th and 13th post-burn day showed reduction in Fc receptor expression of normal PMN cells, whereas sera obtained a month after the injury exhibited no inhibitory effect. Non-survivors sera inhibited Fc receptor expression of normal PMN cells on 5th, 13th and 21st post-burn days. The appearance, increase and disappearance of immature PMN cells in the circulation was correlated with the clinical progress of the patient. Mechanisms involved in the aberrations and its implications are discussed.

Adolescent↗
PubMed1986

Hepatic macrophage complement receptor clearance function following injury.

Previous work has demonstrated that in vivo hepatic macrophage complement receptor clearance function is depressed following thermal injury. The present study was carried out to determine if complement receptor function depression is associated with other states of depressed host defense. Hepatic complement receptor clearance function was determined from the hepatic uptake of rat erythrocytes coated with antierythrocyte IgM (EIgM) in rats. Receptor function was determined following cannulation of a carotid artery, laparotomy plus enterotomy, hemorrhagic shock, trauma, thermal injury, acute bacteremia, acute endotoxemia, and injection of erythrocyte stroma, gelatinized lipid emulsion, or colloidal carbon. Hepatic uptake of EIgM was depressed following each of these experimental interventions except arterial cannulation. This effect was shown not to be due to a decrease in hepatic blood flow or depletion of complement and was therefore due to a depression in hepatic macrophage complement receptor clearance function. Thus, impairment of hepatic macrophage complement receptor function is associated with several states of depressed host defense.

Animals↗
PubMed1990

Phagocytosis of leprosy bacilli is mediated by complement receptors CR1 and CR3 on human monocytes and complement component C3 in serum.

Mycobacterium leprae, an obligate intracellular pathogen, invades and multiplies within host mononuclear phagocytes. To understand M. leprae invasion better, we have investigated the role of phagocyte receptors and bacterium-bound ligands in phagocytosis of M. leprae by human monocytes. Complement receptors CR1 and CR3 mediate adherence and phagocytosis of M. leprae in nonimmune serum. Two MAbs used in combination against CR3 inhibit adherence by up to 90 +/- 3%. Two MAbs used in combination against CR1 and CR3 inhibit adherence by up to 70 +/- 1%. Single MAbs against CR1 or CR3 consistently inhibit adherence by 38-55%. In contrast, MAbs against other monocyte surface molecules, alone or in combination, do not significantly influence adherence. As studied by electron microscopy, 100% of monocyte-associated M. leprae are ingested in the presence of nonimmune serum and MAbs against CR3 markedly inhibit ingestion. Complement receptors CR1 and CR3 also mediate the low level of adherence observed in the absence of serum. Serum complement component C3 serves as a ligand on the bacterial surface in monocyte phagocytosis of M. leprae. Adherence of M. leprae to monocytes is enhanced by preopsonization (3.1 +/- 1.1-fold increase) and is markedly reduced in less than 0.5% fresh serum (66 +/- 7% reduction) or heat-inactivated serum (68 +/- 3% reduction). Adherence is also markedly reduced in C3- or factor B-depleted serum; repletion with purified C3 or factor B increases adherence 4.3 +/- 0.8- and 2.6 +/- 0.2-fold, respectively. C3 is fixed to M. leprae by the alternative pathway of complement activation, as determined by a whole bacterial cell ELISA. By electron microscopy, monocytes ingest M. leprae by conventional phagocytosis. This study demonstrates that (a) human monocyte complement receptors CR1 and CR3 mediate phagocytosis of M. leprae; (b) complement component C3 on the bacterial surface serves as a ligand for complement receptors; (c) complement component C3 binds to M. leprae by the alternative pathway of complement activation; and (d) monocytes phagocytize M. leprae by conventional phagocytosis.

Adult↗
PubMed1995

Priming of human polymorphonuclear neutrophilic leukocytes by insulin-like growth factor I: increased phagocytic capacity, complement receptor expression, degranulation, and oxidative burst.

Insulin-like growth factor I (IGF-I) is a GH-dependent peptide regulating mammalian growth that seems to be of importance for the normal development and function of the immune system. Polymorphonuclear neutrophilic leukocytes (PMNLs) are terminally differentiated phagocytes essential for host defense, and in the present study, recombinant human IGF-I was shown to be a powerful primer of mature human PMNLs. IGF-I augmented the PMNL phagocytosis of both immunoglobulin G-opsonized Staphylococcus aureus and complement-opsonized Candida albicans. In addition, the growth factor increased PMNL complement receptor expression [complement receptors 1 (CD35) and 3 (CD11b)] and primed the cells to stronger f-met-leu-phe-induced degranulation of both specific and azurophilic granules [markers: CD11b, CD35 and CD67 (specific granules); CD63 (azurophilic granules)]. In contrast, IGF-I did not alter the PMNL surface expression of Fc gamma RI (CD64), Fc gamma RII (CDw32), or Fc gamma RIII (CD16). PMNLs exposed to IGF-I increased their f-met-leu-phe and phorbol myristate acetate-induced oxidative burst, as evaluated by hydrogen peroxide production, whereas IGF-I did not influence PMNL actin polymerization. The priming of PMNLs by IGF-I was dependent on time and concentration, and saturating amounts of a monoclonal antibody to the IGF-I receptor blocked the priming of PMNLs by this peptide. These experiments demonstrate that IGF-I can selectively stimulate mature PMNL functions, providing further evidence for the interaction between the immune and the endocrine systems.

Actins↗
PubMed1991

Molecular interactions of complement receptors on B lymphocytes: a CR1/CR2 complex distinct from the CR2/CD19 complex.

The complement system augments the humoral immune response to low concentrations of antigen. This effect may be partly mediated by complement receptors on the surface of B lymphocytes that bind immunogenic complexes bearing fragments of C3 and C4. We have shown by immunoprecipitation analysis that the two complement receptors expressed by B lymphocytes, complement receptor 1 (CR1) and CR2, form a detergent-sensitive complex on the surface of tonsillar B lymphocytes and on K562 erythroleukemia cells that were co-transfected with cDNAs encoding CR1 and CR2. The CR1/CR2 complex is distinct from the CR2/CD19 complex and may assist B cell activation by efficiently capturing C3b-containing immunogens and maintaining such immunogens on the B cell after CR1 and factor I-mediated cleavage to iC3b and C3dg. The complement activating immunogen may then trigger signal transduction by the CR1/CR2 complex, the CR2/CD19 complex, or membrane immunoglobulin.

Antigens, CD19↗
PubMed1990

Characterization of murine complement receptor type 2 and its immunological cross-reactivity with type 1 receptor.

We have previously demonstrated that some mAbs prepared against mouse complement receptor type 1 (CR1) bind a 150,000 Mr protein in addition to the 190,000 Mr CR1 protein. We now identify the 150,000 Mr murine protein as complement receptor type 2 (CR2), since: (i) one of the monoclonal antibodies that bind this protein inhibits rosette formation between mouse B cells and C3d-bearing sheep erythrocytes; (ii) as is known for human CR2, this protein is present on B lymphocytes but not T lymphocytes; and (iii) this protein must have affinity for C3b, since it has weak factor I cofactor activity. In addition, this protein resembles the 145,000 Mr human CR2 molecule in size. Since four of the five mAbs that were produced by immunization with CR1 also bound CR2, and they bind to different CR1 epitopes, it seems that murine CR1 and CR2 share multiple epitopes. Injection of mice with one of the CR1-CR2 cross-reactive mAbs almost eliminated both CR1 and CR2 expression, but did not decrease B cell numbers or the expression of B cell IgM, Ia, or B220 antigens. In contrast, injection of mice with a non-cross-reactive anti-CR1 antibody only modulated CR1 expression. These antibodies should thus provide useful tools for the study of the in vivo roles of B cell complement receptors.

Animals↗
PubMed1988

Absence of complement receptor type 3 and lymphocyte function antigen 1 causing deficient phagocyte and lymphocyte functions.

We describe a patient with delayed umbilical cord detachment, recurrent bacterial infections, and inability to form pus, despite persistent leucocytosis. Immunofluorescence studies with specific monoclonal antibodies showed a severe deficiency in the expression of alpha-chains of the receptor for the C3bi fragment of C3, complement receptor type 3, and the lymphocyte function antigen 1 molecule, found on neutrophil, monocyte and lymphocyte membranes. These membrane antigen defects were responsible for abnormalities in adhesive cell functions. Polymorphonuclear leucocytes demonstrated a markedly reduced chemiluminescence response as well as an impaired nitroblue tetrazolium test and superoxide generation to a particulate stimulus (zymosan), while the responses to a soluble stimulus (phorbol myristate acetate) were normal. In addition, random migration und chemotactic response to zymosan-activated serum were impaired. The lymphocytes demonstrated abolished natural killer cell cytotoxicity as well as abnormal humoral immunity and a lack of antibody response to pertussis and tetanus antigens.

Antigens, Differentiation↗
PubMed1985

Immunologic subsets in B cell lymphomas defined by surface immunoglobulin isotype and complement receptor--their relationship to survival.

Cell surface marker profiles were studied on cell suspensions from monoclonal B cell lymphomas. Surface immunoglobulin (sIg) was examined in 178 cases, whereas combined data with sIg and receptors for complement (C3) were available in 99/178 cases. The results showed that B cell lymphomas can be divided into distinct immunological subsets according to surface marker expression. Whereas some histologic subgroups (diffuse centroblastic/centrocytic, centrocytic, immunocytoma) (Kiel classification) consisted of few immunological subtypes, others were more heterogeneous (follicular centroblastic/centrocytic, centroblastic, lymphocytic). By combining immunological and histological subgroups, more than 40 phenotypes could be identified; this diversity most likely reflects, the heterogeneity of the B cell compartment. As part of the same study the prognostic significance of cell marker phenotypes was examined. Survival analysis undertaken on 149/178 patients did not uncover any significant relationship between type of heavy or light chain expression, C3 receptor expression and clinical outcome. Our data do not confirm recent findings that the type of immunological phenotype may be of prognostic significance.

Aged↗
PubMed1984

Analysis of C3-receptor activity on human B-lymphocytes and isolation of the complement receptor type 2 (CR2).

The rosetting of defined C3-fragment-coated sheep erythrocytes to B-cell-enriched tonsil lymphocytes was measured. The rosetting lymphocytes were homogeneous with respect to expression of C3b, iC3b and C3d receptors. Isolation of receptors for C3 fragments from surface-radioiodinated lymphocytes by affinity chromatography on immobilized C3u, iC3b and C3d,g produced two proteins with partially overlapping specificities. A protein of 240 000 Mr, recognized by the monoclonal antibody To5 and identified as CR1 (complement receptor type 1), had affinity for C3u and iC3b. A protein of 145 000 Mr, recognized by the monoclonal antibody B2, had affinity for all three C3 fragments. Inhibition of rosetting by antibodies to these proteins indicates that CR1 is responsible for C3b-mediated rosetting and that the 145000-Mr receptor (CR2) is responsible for C3d-mediated rosetting. Partial inhibition by both anti-CR1 and anti-CR2 antibodies of iC3b-mediated rosetting indicates that both receptors are involved in iC3b-mediated rosetting. No other protein appears to be involved in tonsil B-cell rosetting to C3-fragment-coated cells. A method for preparing CR2 from tonsil lymphocytes based on affinity chromatography on C3d,g-Sepharose has been developed. Forty tonsil pairs (2 X 10(10) B-cells) yield about 40 micrograms of pure protein equivalent to a purification of 6500-fold from a detergent extract.

Antibodies↗
PubMed1990

Expression of the complement receptors CR1 and CR3 and the type III Fc gamma receptor on neutrophils from newborn infants and from fetuses with Rh disease.

Developmental defects in neutrophil function, including diminished expression of plasma membrane receptors, may play an important role in the susceptibility of the newborn infant to infection. We used monoclonal antibodies and flow cytometry to study the expression of complement receptor type one (CR1), complement receptor type three (CR3), and Fc gamma receptor type three (FcRIII) on neutrophils from six fetuses with Rh disease, 10 preterm infants, nine term infants, and nine adults. Expression of the complement receptors on unstimulated cells was similar for all groups, but significant differences in complement receptor expression were observed after stimulation with N-formyl-methionyl-leucyl-phenylalanine (FMLP). Fetal, preterm, and term infant neutrophils expressed less CR3 than FMLP-stimulated neutrophils of adults [61 +/- 2, 48 +/- 4, and 66 +/- 4% (mean +/- SEM) of the mean for adults, p less than 0.05]. FMLP-stimulated CR1 expression for these groups was 61 +/- 6, 73 +/- 6, and 91 +/- 9% of the adult mean (p less than 0.05, fetal versus term infant and adult). Expression of both CR3 and CR1 increased with postconceptional age in the infants (r2 = 0.49, p less than 0.001 for CR3; r2 = 0.23, p less than 0.05 for CR1). Neutrophils of the preterm and term infants expressed less FcRIII than adult neutrophils (68 +/- 10 and 77 +/- 7% of the adult mean, p less than 0.05, for FMLP-stimulated cells), whereas fetal neutrophil FcRIII expression did not differ from that of the adult.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Differentiation↗
PubMed1981

Fc and complement receptors on malignant tumor cells.

The Fc-C'-receptor-positive cells were investigated in tumor cell suspensions from 196 malignant tumors. The number of EA (Fc) and EAC' (C') rosettes was determined; the rosette-forming cells were identified cytologically, the cell suspensions were exposed to carbon particles, and they were grown in tissue culture. The results suggest that Fc or C' receptors might be present in malignant tumor cells as well as in host defence (inflammatory) cells invading the tumor.

Cell Membrane↗
PubMed1991

Detection of transmembrane linkages between immunoglobulin or complement receptors and the neutrophil's cortical microfilaments by resonance energy transfer microscopy.

By exploiting the 1/r4 (where r is the separation distance between fluorochromes) dependence of energy transfer between parallel lamellae, we have observed transmembrane energy transfer between membrane receptors and cortical microfilaments. Receptors were labeled with donor- or acceptor-conjugated Fab fragments, whereas microfilaments were labeled with acceptor- or donor-conjugated phalloidin reagents. Energy transfer was imaged by optical microscopy. We report that cell surface receptors can be constitutively unlinked, linked or inducibly linked to microfilaments.

Actin Cytoskeleton↗
PubMed1999

Monocyte activation in rheumatoid arthritis (RA): increased integrin, Fc gamma and complement receptor expression and the effect of glucocorticoids.

The aim of this work was to study the expression of beta 1- and beta 2-integrins, CR1, CD44 and Fc gamma receptors on peripheral blood monocytes in RA. The expression of these receptors was measured by flow cytometry, before and after treatment with low-dose prednisolone. Expression of the same receptors was also measured before and after treatment with metyrapone, a substance that inhibits the synthesis of cortisol in the adrenals. The expression of the beta 2-integrins CD11a, CD11b and CD18, of CD35 (CR1), and of Fc gamma RII and Fc gamma RI (CD32 and CD64) on monocytes was elevated in the RA patients compared with healthy controls, while the expression of the beta 1-integrins (CD29, CD49d, CD49f) was unaffected. A significant correlation between monocyte expression of CD64 and C-reactive protein (CRP), and blood platelet count, respectively, was found in the group of patients with RA. After 4-6 weeks of treatment with low-dose prednisolone, the expression on the monocytes of CD11a, CD11b, CD18, CD35, CD32 and CD64 was normalized. A significant correlation (r = 0.64, P = 0.02) was found between the decrease in expression of CD11b and clinical improvement after prednisolone treatment. Two days of metyrapone treatment, which significantly lowered the serum cortisol levels, elevated the expression of CD35 and CD49f. Priming of peripheral monocytes seems to be one of the mechanisms behind the recruitment of monocytes to the rheumatoid synovium. One reason for the good clinical effects of prednisolone in RA could be a down-regulation of adhesion and phagocytosis receptors on monocytes.

Adult↗
PubMed1988

Complement receptor type 3 (CR3) binds to an Arg-Gly-Asp-containing region of the major surface glycoprotein, gp63, of Leishmania promastigotes.

The major surface glycoprotein of Leishmania promastigotes, gp63, was isolated and reconstituted into a lipid membrane immobilized on the surface of 5-micron-diameter silica beads. These beads bound to the macrophage (MO), and the extent of binding correlated with the density of gp63 on the bead. The bead thus facilitated analysis of the binding specificity of a single ligand, gp63, without contribution from other molecules present on the surface of intact promastigotes. Plating of MO onto substrates coated with antibodies directed against several cell surface receptors indicated that the complement receptor CR3 was necessary for binding gp63. CR3 recognizes a portion of C3 that contains the sequence R G D. Since gp63 also contains such a sequence, we tested the ability of a synthetic peptide based on the R G D-containing region of gp63 to inhibit the binding of gp63 beads. The R G D-containing peptide from gp63 inhibited the binding of both gp63 beads and EC3bi to MO. Similarly, peptides previously shown to inhibit the binding of C3bi also inhibited the attachment of gp63 beads. The synthetic peptide from the R G D region of gp63 also reduced the binding of intact promastigotes to MO. These results indicate that gp63 binds directly to CR3.

Amino Acid Sequence↗
PubMed2003

Increased respiratory burst and increased expression of complement receptor-3 (CD11b/CD18) and of IL-8 receptor-A in neutrophil granulocytes from newborns after vaginal delivery.

To study neutrophil activation in cord blood as a function of the mode of delivery, we performed analysis of the function of neutrophil granulocytes by assessing their ability to produce reactive oxygen products (ROP) as well as neutrophil cell surface expression of CD11b/CD18 and interleukin (IL)-8 receptors quantified with flow cytometry. Plasma levels of granulocyte colony-stimulating factor (G-CSF) were measured using an immunoassay. Neutrophil granulocytes were derived from cord blood of term newborns delivered vaginally (n = 20) and by cesarean section (n = 10), and, for comparison, from adult peripheral blood (n = 15). Blood neutrophil counts and the capacity of neutrophil granulocytes to produce ROP in response to stimulation with Escherichia coli was increased in newborns after vaginal delivery as compared to newborns delivered by cesarean section. The level of expression of the adhesion molecule/complement receptor CD11b/CD18 and the chemokine receptor IL-8 RA was also higher after vaginal delivery. Plasma concentrations of G-CSF in cord blood of newborns were higher than those of adults with no difference detectable between vaginal delivery and cesarean section. The data demonstrate a higher functional responsiveness and a higher expression level of functionally important receptors in neutrophils after vaginal delivery possibly due to activation of neutrophil granulocytes during labor.

Adult↗