PubMed Health⌕ Search

Biomedical subjects

J G van de Winkel

Publications and source records attributed to J G van de Winkel.

At least 19 recordsLinked to original sources
PubMed2001

The cytoplasmic domain of FcgammaRIIA (CD32) participates in phagolysosome formation.

Signaling motifs located within the cytoplasmic domain of certain receptors contribute to lysosome fusion. Most studies have described lysosome fusion with respect to endocytic receptors. Phagolysosome fusion has not been extensively studied. To test the hypothesis that the tail of FcgammaRIIA participates in phagolysosomal fusion, a "reverse" genetic complementation system was used. It was previously shown that complement receptor type 3 (CR3) can rescue the phagocytic activity of a mutant FcgammaRIIA lacking its cytoplasmic domain (tail-minus form). This system has allowed us to study Fcgamma receptor-dependent phagocytosis and phagolysosome fusion in the presence and absence of the cytoplasmic domain of FcgammaRIIA. Fluorescent dextran was used to label lysosomes. After target internalization, wild-type FcgammaRIIA-mediated phagolysosome formation was observed as indicated by colocalization of fluorescent dextran and the phagosome. In addition, when studying mutants of FcgammaRIIA containing a full-length cytoplasmic tail with the 2 ITAM tyrosines mutated to phenylalanine, (1) phagocytosis was abolished, (2) CR3 restored phagocytosis, and (3) lysosomal fusion was similar to that observed with the wild-type receptor. In contrast, in the presence of CR3 and the tail-minus form of FcgammaRIIA, internalized particles did not colocalize with dextran. Electron microscopy revealed that the lysosomal enzyme acid phosphatase colocalized with immunoglobulin G-coated targets internalized by wild-type FcgammaRIIA but not by tail-minus FcgammaRIIA and CR3. Thus, the tail of FcgammaRIIA contributes to phagolysosome fusion by a mechanism that does not require a functional ITAM sequence.

Acid Phosphatase↗
PubMed2001

Fc receptor-mediated immunity against Bordetella pertussis.

The relevance of specific Abs for the induction of cellular effector functions against Bordetella pertussis was studied. IgG-opsonized B. pertussis was efficiently phagocytosed by human polymorphonuclear leukocytes (PMN). This process was mediated by the PMN IgG receptors, FcgammaRIIa (CD32) and FcgammaRIIIb (CD16), working synergistically. Furthermore, these FcgammaR triggered efficient PMN respiratory burst activity and mediated transfer of B. pertussis to lysosomal compartments, ultimately resulting in reduced bacterial viability. Bacteria opsonized with IgA triggered similar PMN activation via FcalphaR (CD89). Simultaneous engagement of FcalphaRI and FcgammaR by B. pertussis resulted in increased phagocytosis rates, compared with responses induced by either isotype alone. These data provide new insights into host immune mechanisms against B. pertussis and document a crucial role for Ig-FcR interactions in immunity to this human pathogen.

Antibodies, Bacterial↗
PubMed2001

Therapeutic efficacy of intravenous immunoglobulin preparations depends on the immunoglobulin G dimers: studies in experimental immune thrombocytopenia.

The clinical benefit of intravenous immunoglobulin (IVIG) preparations in the treatment of immune thrombocytopenic purpura (ITP) is supposed to be mediated by blockade of Fc gamma receptor--bearing phagocytes. In 2 experimental models for ITP, it is shown that the therapeutic efficacy of IVIG preparations is related to the IgG dimer content present in these preparations. A rat monoclonal antibody (mAb; MWReg30) directed to the murine platelet-specific integrin alpha(IIb)beta(3) (gpIIb/IIIa) was administered intraperitoneally either as bolus injection or continuous infusion. With bolus injection, the circulating platelet count dropped to almost zero within 3 hours. Pretreatment with cobra venom factor did not affect platelet depletion, whereas pretreatment with anti-Fc gamma RII/III mAb 2.4G2 or IVIG greatly reduced platelet clearance. With continuous infusion, platelet numbers reached a steady state after 4 days, at approximately 25% of control. This reduction in platelets was, however, not observed in mice deficient for the FcR gamma-chain, lacking Fc gamma RI, Fc gamma RIII, and Fc gamma RIII(-/-) mice. Infusion of a single dose of IVIG with a high IgG dimer content on the 4th day--ie, mimicking therapeutic administration--resulted in a platelet increase for several days. IVIG predominantly consisting of monomeric IgG had no effect on platelet numbers. In conclusion, continuous infusion of MWReg30 induces thrombocytopenia in mice by enhancing Fc gamma receptor--mediated clearance of platelets. In this model, it is shown that IgG dimers present in IVIG preparations are responsible for the increase in platelet counts. (Blood. 2001;98:1095-1099)

Animals↗
PubMed2001

Neutrophil Fc gamma RI as target for immunotherapy of invasive candidiasis.

Invasive candidiasis represents a life-threatening disease for immunocompromised patients. This study focused on new immunotherapeutic approaches for systemic Candida albicans infections in a human FcgammaRI-transgenic mouse model. FcgammaRI (CD64) is a potent immunoactivating receptor on phagocytic and dendritic cells. In vivo targeting of C. albicans toward neutrophil-FcgammaRI by bispecific Abs and G-CSF effectively protected FcgammaRI-transgenic mice from lethal candidiasis. Nontransgenic mice were not protected, and treatment with bispecific Ab or G-CSF alone did not reduce mortality. Furthermore, infected FcgammaRI-transgenic mice developed high titers of anti-C. albicans IgG, and survival was extended on secondary infection without further treatment. These findings document the capacity of FcgammaRI to initiate potent anti-C. albicans immunity and support the development of FcgammaRI-directed immunotherapy of invasive fungal disease.

Adjuvants, Immunologic↗
PubMed2001

Enhancement of polymorphonuclear cell-mediated tumor cell killing on simultaneous engagement of fcgammaRI (CD64) and fcalphaRI (CD89).

Antibodies can efficiently induce antitumor responses via recruitment of Fc receptor-bearing cytotoxic cells. Polymorphonuclear (PMN) cells represent attractive effector cells for antibody-directed immunotherapy. This, because activated PMN cells coexpress the class I receptors for IgG (FcgammaRI, CD64) and IgA (FcalphaRI, CD89), which are potent cytotoxic trigger molecules. Both receptors, however, require the FcR gamma chain for signaling. In this study, we show that FcgammaRI and FcalphaRI can trigger function independently of one another and do not cross-compete for the FcR gamma chain. FcalphaRI proved more efficient in initiating early signaling events and effector functions, such as redirected tumor cell killing and generation of superoxide. In addition, simultaneous engagement of FcgammaRI and FcalphaRI resulted in enhanced tumor cell lysis. These data support the development of concepts in which both FcgammaRI and FcalphaRI on PMN cells are targeted for tumor therapy.

Animals↗
PubMed2001

Mac-1 (CD11b/CD18) is essential for Fc receptor-mediated neutrophil cytotoxicity and immunologic synapse formation.

Receptors for human immunoglobulin (Ig)G and IgA initiate potent cytolysis of antibody (Ab)-coated targets by polymorphonuclear leukocytes (PMNs). Mac-1 (complement receptor type 3, CD11b/CD18) has previously been implicated in receptor cooperation with Fc receptors (FcRs). The role of Mac-1 in FcR-mediated lysis of tumor cells was characterized by studying normal human PMNs, Mac-1-deficient mouse PMNs, and mouse PMNs transgenic for human FcR. All PMNs efficiently phagocytosed Ab-coated particles. However, antibody-dependent cellular cytotoxicity (ADCC) was abrogated in Mac-1(-/-) PMNs and in human PMNs blocked with anti-Mac-1 monoclonal Ab (mAb). Mac-1(-/-) PMNs were unable to spread on Ab-opsonized target cells and other Ab-coated surfaces. Confocal laser scanning and electron microscopy revealed a striking difference in immunologic synapse formation between Mac-1(-/-) and wild-type PMNs. Also, respiratory burst activity could be measured outside membrane-enclosed compartments by using Mac-1(-/-) PMNs bound to Ab-coated tumor cells, in contrast to wild-type PMNs. In summary, these data document an absolute requirement of Mac-1 for FcR-mediated PMN cytotoxicity toward tumor targets. Mac-1(-/-) PMNs exhibit defective spreading on Ab-coated targets, impaired formation of immunologic synapses, and absent tumor cytolysis.

Animals↗
PubMed2001

Multiplex screening for functionally rearranged immunoglobulin variable regions reveals expression of hybridoma-specific aberrant V-genes.

Modification of antibody effector functions is commonly performed by chimerization or humanization. Cloning of antibody variable regions from hybridomas represents a first step that is frequently hampered by the expression of non-functionally rearranged variable regions in hybridoma cells that originate from MOPC21-derived fusion partners. We now present a simple method to clone functionally rearranged V-genes, based on V-gene-specific multiplex PCR screening. Using this method we document the expression of aberrant V-genes that originate from the original B-cell used for the hybridoma generation, not from the fusion partner, and are - thus - hybridoma specific.

Animals↗
PubMed2001

Mechanisms of G-CSF- or GM-CSF-stimulated tumor cell killing by Fc receptor-directed bispecific antibodies.

Studies with gene-modified mice have recently reinforced the importance of Fc receptor-mediated effector mechanisms for the therapeutic efficacy of rituxan and herceptin - two clinically approved antibodies for the treatment of tumor patients. We investigated Fc receptor-dependent tumor cell killing by mononuclear and granulocytic effector cells - comparing human IgG1 antibodies against CD20 or HER-2/neu with their respective FcgammaRI (CD64)-, FcgammaRIII (CD16)-, or FcalphaRI (CD89)-directed bispecific derivatives. With blood from healthy donors as effector source, human IgG1 and FcgammaRIII (CD16)-directed bispecific antibodies proved most effective in recruiting mononuclear effector cells, whereas tumor cell killing by granulocytes was most potently triggered by FcalphaRI-directed bispecific constructs. Granulocyte-mediated tumor cell lysis was significantly enhanced when blood from G-CSF- or GM-CSF-treated patients was investigated. Interestingly, however, both myeloid growth factors improved effector cell recruitment by different mechanisms, which were furthermore dependent on the tumor target antigen, and on the selected cytotoxic Fc receptor.

Animals↗
PubMed2001

Human antibodies as next generation therapeutics.

Antibodies and antibody derivatives constitute twenty five percent of therapeutics currently in development, and a number of therapeutic monoclonal antibodies have recently reached the market. All antibodies approved by the US Food and Drug Administration, however, contain mouse protein sequences. These partially murine antibodies, therefore, have the potential to elicit allergic or other complications when used in human patients. Recent developments aim to reduce or eliminate murine components, and fully human antibodies are rapidly becoming the norm. A number of technologies exist which enable the development of 100% human antibodies.

Animals↗
PubMed2001

IgA and the IgA Fc receptor.

IgA has traditionally been regarded a non-inflammatory antibody. This might indeed be true for secretory IgA (SIgA), which exerts its function at mucosal surfaces where commensal microorganisms and dietary antigens prevail. Serum IgA, however, potently triggers (pro)-inflammatory activity upon binding to the myeloid IgA receptor, FcalphaRI. Here, new insights in the roles of IgA and FcalphaRI are addressed and a model integrating the various functions of IgA in immunity is discussed.

Animals↗
PubMed2001

Inflammation in autoimmunity: receptors for IgG revisited.

During the past decade, our knowledge of Fc receptor interactions in inflammation has increased dramatically owing to the availability of single and multiple Fc-receptor-deficient mice. The deletion of activating Fc gamma receptors protects against inflammation in models of immune-complex-mediated diseases, whereas the deletion of inhibitory Fc gamma receptors triggers increased susceptibility to immune-complex-induced inflammation. These new insights have a profound impact on our understanding of inflammation in autoimmune diseases, such as systemic lupus erythematosus (SLE). Comprehending the complex interactions between activating and inhibitory Fc gamma receptors might lead to new therapeutic approaches for human diseases, including SLE.

Animals↗
PubMed2001

Cytotoxicity of anti-CD64-ricin a chain immunotoxin against human acute myeloid leukemia cells in vitro and in SCID mice.

Blast cells from patients with acute myeloid leukemia (AML) commonly express CD64, the high-affinity receptor for immunoglobulin G (FcgammaRI). An immunotoxin (MDX-44) was constructed by coupling humanized anti-CD64 monoclonal antibody (mAb) H22 via a bivalent linker to deglycosylated ricin A-chain (RA). Human leukemia cell lines were incubated with MDX-44 or H22/free RA. The effect of MDX-44 on the proliferation of leukemia cells was assessed by [(3)H]thymidine incorporation. In the presence of interferon-gamma (IFN-gamma), MDX-44 significantly inhibited the proliferation of CD64(+) HL-60, NB4, and U937 cells in 72-h cultures in a dose-dependent manner. The mechanism of action appeared to be the induction of apoptosis, as measured by propidium iodide staining and flow cytometry analysis. However, CD64(-) KG-1a and Daudi cells were not affected by MDX-44/IFN-gamma. Incubating HL-60 cells with MDX-44/IFN-gamma resulted in a 99% decrease in colony-forming units, whereas colony-forming cells in normal bone marrow were not significantly suppressed by such treatment. Cells from 60% of AML patients (6/10) were inhibited by MDX-44/IFN-gamma, and the inhibition was correlated with CD64 expression on these cells (r = 0.65). In a human AML model in NOD/SCID mice, MDX-44/IFN-gamma inhibited 95-98% of peritoneal exudate AML cell proliferation and 85-90% of solid leukemia masses. The effect of MDX-44 on AML cells was dependent on activation of cells by IFN-gamma. MDX-44/IFN-gamma may have value in the therapy of AML cells expressing cell-surface CD64.

Acute Disease↗
PubMed2001

Effective in vitro clearance of Porphyromonas gingivalis by Fc alpha receptor I (CD89) on gingival crevicular neutrophils.

Porphyromonas gingivalis has been implicated as a causative pathogen in periodontitis. Immunotherapeutic approaches have recently been suggested to aid in the clearance of P. gingivalis from disease sites. Because antibody-Fc receptor (FcR) interactions play a role in the effector functions of polymorphonuclear neutrophils (PMN), we evaluated which FcR on PMN from gingival crevicular fluid (GCF) serves as an optimal target molecule for FcR-directed immunotherapy. GCF PMN and peripheral blood (PB) PMN from adult periodontitis patients were analyzed for their immunoglobulin G (IgG) and IgA FcR (Fc gamma R and Fc alpha R, respectively) expression and function by studying IgG- and IgA-mediated elimination of P. gingivalis. GCF PMN exhibited higher Fc alpha RI and Fc gamma RI levels and lower Fc gamma RIIa and Fc gamma RIIIb levels than PB PMN. Functional studies revealed that GCF PMN exhibited less of a capacity to phagocytose and kill IgG1-opsonized P. gingivalis than PB PMN. IgA1-mediated phagocytosis and killing capacity was, however, comparable between GCF PMN and PB PMN. In summary, these in vitro results document that Fc alpha RI represents a candidate target for FcR-directed immunotherapy for the clearance of P. gingivalis.

Adult↗
PubMed2001

Immunoglobulin A-mediated protection against Bordetella pertussis infection.

Infection with Bordetella pertussis, the causative agent of pertussis (whooping cough) in humans, is followed by the production of antibodies of several isotypes, including immunoglobulin A (IgA). Little is known, however, about the role of IgA in immunity against pertussis. Therefore, we studied targeting of B. pertussis to the myeloid receptor for IgA, FcalphaRI (CD89), using either IgA purified from immune sera of pertussis patients or bispecific antibodies directed against B. pertussis and FcalphaRI (CD89 BsAb). Both IgA and CD89 BsAb facilitated FcalphaRI-mediated binding, phagocytosis, and bacterial killing by human polymorphonuclear leukocytes (PMNL) and PMNL originating from human FcalphaRI-transgenic mice. Importantly, FcalphaRI targeting resulted in enhanced bacterial clearance in lungs of transgenic mice. These data support the capacity of IgA to induce anti-B. pertussis effector functions via the myeloid IgA receptor, FcalphaRI. Increasing the amount of IgA antibodies induced by pertussis vaccines may result in higher vaccine efficacy.

Animals↗
PubMed2001

Effector function activities of a panel of mutants of a broadly neutralizing antibody against human immunodeficiency virus type 1.

The human antibody immunoglobulin G1 (IgG1) b12 neutralizes a broad range of human immunodeficiency virus-type 1 (HIV-1) isolates in vitro and is able to protect against viral challenge in animal models. Neutralization of free virus, which is an antiviral activity of antibody that generally does not require the antibody Fc fragment, likely plays an important role in the protection observed. The role of Fc-mediated effector functions, which may reduce infection by inducing phagocytosis and lysis of virions and infected cells, however, is less clear. To investigate this role, we constructed a panel of IgG1 b12 mutants with point mutations in the second domain of the antibody heavy chain constant region (CH2). These mutations, as expected, did not affect gp120 binding or HIV-1 neutralization. IgG1 b12 mediated strong antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) of HIV-1-infected cells, but these activities were reduced or abrogated for the antibody mutants. Two mutants were of particular interest. K322A showed a twofold reduction in FcgammaR binding affinity and ADCC, while C1q binding and CDC were abolished. A double mutant (L234A, L235A) did not bind either FcgammaR or C1q, and both ADCC and CDC functions were abolished. In this study, we confirmed that K322 forms part of the C1q binding site in human IgG1 and plays an important role in the molecular interactions leading to complement activation. Less expectedly, we demonstrate that the lower hinge region in human IgG1 has a strong modulating effect on C1q binding and CDC. The b12 mutants K322A and L234A, L235A are useful tools for dissecting the in vivo roles of ADCC and CDC in the anti-HIV-1 activity of neutralizing antibodies.

Antibody-Dependent Cell Cytotoxicity↗
PubMed2001

Increased frequency of FcgammaRIIIb-NA1 allele in periodontitis-resistant subjects in an elderly Japanese population.

Many elderly people show minimum periodontal tissue destruction, which might be partly due to genetic advantages in host immune response against periodontopathic bacteria. The human IgG Fc receptor IIIb on neutrophils bears a NA1-NA2 polymorphism. The FcgammaRIIIb-NA1 displays a more efficient interaction with IgG1- and IgG3-opsonized bacteria, compared with the FcgammaRIIIb-NA2. We investigated a 70-year-old Japanese population (n = 599) to determine whether the FcgammaRIIIb polymorphism was associated with resistance to periodontitis. Among subjects with > or = 20 teeth present, periodontitis-resistant (n = 46) and periodontitis-susceptible groups (n = 73) were selected based on the percentage of sites with > or = 4 mm probing attachment loss in the entire dentition. The FcgammaRIIIb-NA1 allotype was overrepresented in the periodontitis-resistant group, compared with the periodontitis-susceptible group (chi2 = 4.89, p = 0.03, odds ratio = 1.87, 95% CI, 1.07 to 3.28). This suggests that FcgammaRIIIb-NA1 may be associated with resistance to periodontitis.

Aged↗
PubMed2001

The Fc gamma receptor genotype as a severity factor for chronic periodontitis in Japanese patients.

BACKGROUND: Functional polymorphisms of immunoglobulin G (IgG) Fc receptors (Fc gamma R) have been shown to be associated with generalized aggressive periodontitis (GAgP) or recurrence of chronic periodontitis (CP) in Japanese patients. The purpose of this study was to evaluate whether Fc gamma R polymorphisms are also associated with severity of CP. METHODS: Fifty Japanese non-smoking patients with severe CP and 39 Japanese non-smoking patients with moderate CP were identified according to established clinical criteria, including measurements of probing depth (PD), clinical attachment level (CAL), and alveolar bone loss (BL). Fc gamma R genotypes for 3 bi-allelic polymorphisms (Fc gamma RIIa-R/H131, Fc gamma RIIIa-158V/F, Fc gamma RIIIb-NA1/NA2) were determined in these CP patients and 64 race-matched, non-smoking healthy controls by means of allele-specific polymerase chain reactions. RESULTS: There was a significant over-representation of Fc gamma RIIIa-158V allele in severe CP patients compared to moderate CP patients (odds ratio 2.03, 95% confidence interval [CI] 1.03-4.01, chi 2 = 4.86, P = 0.028). In addition, we found a strong association between CP severity and Fc gamma R composite genotype comprising Fc gamma RIIIa-158V plus Fc gamma RIIIb-NA2 (severe CP versus moderate CP: odds ratio 4.69, 95% CI 1.52-15.10, chi 2 = 9.35, P = 0.002; severe CP versus healthy controls: odds ratio 4.10, 95% CI 1.62-10.59, chi 2 = 11.13, P = 0.0009). Moreover, CP patients positive for the composite genotype exhibited more severe signs of periodontitis than composite genotype-negative individuals (positive versus negative; mean PD: 3.8 mm versus 3.2 mm, P = 0.005; mean CAL: 4.5 mm versus 3.7 mm, P = 0.005; mean % BL: 37.6% versus 29.9%, P = 0.008). CONCLUSION: Our results document the Fc gamma RIIIa-158V allele and possibly Fc gamma RIIIb-NA2 to be associated with severity of CP in Japanese patients.

Adult↗