PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Antibody effector functions”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1993

Structural motifs involved in human IgG antibody effector functions.

A humanized IgG antibody to CAMPATH-1 antigen (CDw52) is known to be lympholytic both in vitro and in vivo. So as to improve therapeutic potency through protein engineering strategies, we wish to define the structural motifs underlying some of the documented differences in function between human (h) IgG1 and IgG4 forms of the antibody. By the creation of heavy chain domain-switch and intra-domain recombinant antibodies we have established an important role for the carboxy-terminal half of the CH2 domain in determining differential behaviour in antibody-dependent cytotoxicity (ADCC) and in complement lysis. If this same region were necessary for the effector mechanisms that operate in vivo, then it might be possible to improve antibody effector functions by construction of novel antibodies that possess within the one molecule multiple copies of the crucial hinge-CH2 associated structures. Although our previous work suggested that the hIgG4 CAMPATH-1 antibody was ineffective at ADCC, we found this to be so only in some individuals. In others, IgG4, and indeed all the IgG subclasses were able to mediate ADCC. Overall, though, hIgG1 remains the best choice isotype for lytic therapy in vivo.

Amino Acid Sequence↗
PubMed1990

Inhibition of processing of asparagine-linked carbohydrate chains on IgG2a by using swainsonine has no influence upon antibody effector functions in vitro.

Removal of asparagine (Asn)-linked carbohydrate chains from IgG antibody molecules reduces their antibody effector functions such as C activation and FcR binding. We have prepared IgG2a mAb with modified structure of carbohydrate chains by treating the hybridoma cells with swainsonine, which inhibits the processing of Asn-linked carbohydrate chains at the site of action of mannosidase II. These antibodies have obtained the capacity to bind lentil lectin and have become sensitive to endoglycosidase H digestion, indicating the structural changes of oligosaccharides from complex type to hybrid type. They behaved in an identical manner to the normal IgG2a antibodies with regards to extracellular secretion, Ag-binding capacity, C-mediated hemolysis and FcR-mediated functions. Critical moieties of Asn-linked carbohydrate chains on IgG molecules to retain their antibody effector functions were discussed.

Acetylglucosaminidase↗
PubMedDate not supplied

Control of recombinant monoclonal antibody effector functions by Fc N-glycan remodeling in vitro.

N-Glycans at Asn(297) in the Fc domain of IgG molecules are required for Fc receptor-mediated effector functions such as antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). In this study we have specifically remodeled the Fc N-glycans of intact recombinant IgG(1) therapeutic monoclonal antibody (Mab) products, Rituxan and Herceptin, with a soluble recombinant rat beta-1,4-N-acetylglucosaminyltransferase III (rGnTIII) produced by baculovirus-infected insect cells. N-Glycan remodeling in vitro permitted a controlled and selective transfer of a bisecting beta1,4-linked GlcNAc to the core beta-linked mannose of degalactosylated Mab N-glycans to yield Mabs varying in bisecting GlcNAc content from 31% to 85%. This was confirmed by analysis of N-glycans by both normal phase HPLC and MALDI-MS, the latter yielding the expected mass increase of 203.2 Da with no other oligosaccharide modifications evident. ADCC of remodeled Rituxan and Herceptin Mabs was determined using peripheral blood mononuclear cells as effectors and either CD20(+) (SKW6.4 and SU-DHL-4) or Her2(+) (SKBR-3) target cells, respectively. A conserved 10-fold increase in ADCC was observed for both remodeled therapeutic Mabs with high (>80%) bisecting GlcNAc content. In contrast, although the presence of a bisecting GlcNAc had minimal effect on CDC, degalactosylation of Rituxan reduced CDC by approximately half, relative to unmodified (variably galactosylated) control Mab. In summary, our data suggests that in vitro remodeling of therapeutic Mab Fc N-glycans may be utilized to control the therapeutic efficacy of Mabs in vivo and to offer a more "humanized" glycoform profile for recombinant Mab products.

Animals↗
PubMed2006

Modulation of therapeutic antibody effector functions by glycosylation engineering: influence of Golgi enzyme localization domain and co-expression of heterologous beta1, 4-N-acetylglucosaminyltransferase III and Golgi alpha-mannosidase II.

The effector functions elicited by IgG antibodies strongly depend on the carbohydrate moiety linked to the Fc region of the protein. Therefore several approaches have been developed to rationally manipulate these glycans and improve the biological functions of the antibody. Overexpression of recombinant beta1,4-N-acetylglucosaminyltransferase III (GnT-III) in production cell lines leads to antibodies enriched in bisected oligosaccharides. Moreover, GnT-III overexpression leads to increases in non-fucosylated and hybrid oligosaccharides. Such antibody glycovariants have increased antibody-dependent cellular cytotoxicity (ADCC). To explore a further variable besides overexpression of GnT-III, we exchanged the localization domain of GnT-III with that of other Golgi-resident enzymes. Our results indicate that chimeric GnT-III can compete even more efficiently against the endogenous core alpha1,6-fucosyltransferase (alpha1,6-FucT) and Golgi alpha-mannosidase II (ManII) leading to higher proportions of bisected non-fucosylated hybrid glycans ("Glyco-1" antibody). The co-expression of GnT-III and ManII led to a similar degree of non-fucosylation as that obtained for Glyco-1, but the majority of the oligosaccharides linked to this antibody ("Glyco-2") are of the complex type. These glycovariants feature strongly increased ADCC activity compared to the unmodified antibody, while Glyco-1 (hybrid-rich) features reduced complement-dependent cytotoxicity (CDC) compared to Glyco-2 or unmodified antibody. We show that apart from GnT-III overexpression, engineering of GnT-III localization is a versatile tool to modulate the biological activities of antibodies relevant for their therapeutic application.

Animals↗
PubMed1994

Modification of monoclonal antibody carbohydrates by oxidation, conjugation, or deoxymannojirimycin does not interfere with antibody effector functions.

Site-specific attachment of metal chelators or cytotoxic agents to the carbohydrate region of monoclonal antibodies results in clinically useful immunoconjugates [Doerr et al. (1991) Ann Surg 214: 118, Wynant et al. (1991) Prostate 18: 229]. Since the capacity of monoclonal antibodies (mAb) to mediate tumor cell lysis via antibody-dependent cellular cytotoxicity (ADCC) or complement-dependent cytotoxicity (CDC) may accentuate the therapeutic effectiveness of immunoconjugates, we determined whether site-specific modification of mAb carbohydrates interfered with these functions. The chemical modifications examined consisted of periodate oxidation and subsequent conjugation to either a peptide linker/chelator (GYK-DTPA) or a cytotoxic drug (doxorubicin adipic dihydrazide). mAb-associated carbohydrates were also modified metabolically by incubating hybridoma cells in the presence of a glucosidase inhibitor deoxymannojirimycin to produce high-mannose antibody. All four forms (unaltered, oxidized, conjugated and high-mannose) of murine mAb OVB-3 mediated tumor cell lysis via CDC. Similarly, equivalent ADCC was observed with native and conjugated forms of mAb OVB-3 and EGFR.1. ADCC was achieved with different murine effector cells such as naive (NS), poly (I*C)- and lipopolysaccharide-stimulated (SS) spleen cells, or Corynebacterium-parvum-elicited peritoneal cells (PEC). All murine effector cell types mediated tumor cell lysis but differed in potency such that PEC > SS > NS. Excellent ADCC activity was also demonstrable by human peripheral blood mononuclear cells with OVB-3-GYK-DTPA and high-mannose OVB-3 mAb. ADCC activity was detectable in vivo: both native and conjugated OVB-3 inhibited growth of OVCAR-3 xenografts in nude mice primed with C. parvum. In conclusion, modification of mAb carbohydrates did not compromise their in vivo or in vitro biological functions. Therefore, combination therapy using immunomodulators to enhance the effector functions of site-specific immunoconjugates could be seriously contemplated.

1-Deoxynojirimycin↗
PubMed2004

Frontline: Epitope recognition on the myelin/oligodendrocyte glycoprotein differentially influences disease phenotype and antibody effector functions in autoimmune demyelination.

Preliminary observations of humoral immunity against the myelin oligodendrocyte glycoprotein (MOG) in experimental allergic encephalomyelitis (EAE) and human multiple sclerosis (MS) suggest that a subset of anti-MOG autoantibodies directed against conformational epitopes is of pathogenic predominance. Here, we provide proof that in marmoset EAE, autoantibodies reactive against conformational epitopes of MOG are not only responsible for aggravating demyelination, but also an essential factor for disease dissemination in space within the central nervous system, a hallmark for typical forms of human MS. In terms of effector mechanisms, IgG deposition and complement activation occur exclusively in association with presence of these conformational antibodies, while microglial/macrophage activation appears to be a common immunopathological finding regardless of the fine determinant specificity of anti-MOG antibodies. These findings highlight for the first time the complex heterogeneity of function and pathogenicity in the polyclonal anti-MOG antibody repertoire of outbred species. Because the linear and conformational antibody determinants of MOG are shared between marmosets and humans, these results are directly relevant to understanding effector mechanisms of organ damage in MS.

Animals↗
PubMed1998

Identification of the mouse IgG3 receptor: implications for antibody effector function at the interface between innate and adaptive immunity.

Mouse IgG3 appears early in immune responses independently of T cell help and, as such, is an early effector molecule of the immune system. Yet, a specific IgG3 cellular receptor remains undefined. In transfection experiments, mouse Fc gammaRI was clearly able to bind immune complexes of IgG3, whereas mouse Fc gammaRII could not. Furthermore, macrophages from mice expressing Fc gammaRII and Fc gammaRIII but lacking Fc gammaRI were unable to phagocytose IgG3 immune complexes, thus identifying mouse Fc gammaRI as the sole receptor for IgG3 immune complexes. Competition studies demonstrated that monomeric mouse IgG3 could inhibit IgG2a binding to mouse Fc gammaRI with an ID50 approximately 10(-7) M (fivefold lower than IgG2a). The identification of mouse Fc gammaRI as the IgG3 receptor establishes Fc gammaRI as a participant in events at the interface between innate and adaptive immunity, implying a greater role for this receptor in the development of normal and pathologic immune responses than previously recognized.

Animals↗
PubMed1986

Tritrichomonas foetus: preparation of monoclonal antibodies with effector function.

Monoclonal antibodies were prepared against Tritrichomonas foetus and characterized with regard to binding and immune effector activities. Nine of 27 monoclonal antibodies which reacted with T. foetus appeared to bind to the surface of live parasites. Immunoelectron microscopy confirmed the surface binding of two of these. At least six of these surface reactive monoclonal antibodies facilitated complement mediated lysis of T. foetus and one acted as an opsonin for phagocytosis by peripheral blood bovine monocytes. Five surface reactive monoclonal antibodies identified a molecule of approximately 150,000 relative molecular weight on Western blots of whole parasite preparations. These results collectively suggest the 150,000 relative molecular weight molecule may be an important target antigen for the immune response to T. foetus.

Agglutination↗
PubMed2026

Mapping antibody sequences and effector functions across spatial niches.

Antibodies are fundamental to human health but can also drive pathology. Each antibody has a molecular specificity, encoded by their clonally heritable B cell receptor (BCR). Recent advances in spatial transcriptomics coupled with repertoire sequencing have enabled capturing antibody-secreting cells (ASCs) and their clonal BCR within their tissue microenvironment. However, our understanding of antibody production niches remains limited. Furthermore, where antibodies are produced can be distinct from where antibodies exert their effector function. Here, we propose a conceptual spatial framework to distinguish between 'antibody production niches', defined by the ASC, BCR, and niche composition, versus 'antibody functional niches', composed of the antibody, antigen, and effector landscape. We then examine the possibilities and challenges to map and link antibody-encoding sequences and antibody effector functions using current and emerging technologies. Combined, we argue that integrating spatial sequence data with the antibody functional context is essential to decode the architecture of antibody-mediated immunity.

Humans↗
PubMed2006

Engineered antibody Fc variants with enhanced effector function.

Antibody-dependent cell-mediated cytotoxicity, a key effector function for the clinical efficacy of monoclonal antibodies, is mediated primarily through a set of closely related Fcgamma receptors with both activating and inhibitory activities. By using computational design algorithms and high-throughput screening, we have engineered a series of Fc variants with optimized Fcgamma receptor affinity and specificity. The designed variants display >2 orders of magnitude enhancement of in vitro effector function, enable efficacy against cells expressing low levels of target antigen, and result in increased cytotoxicity in an in vivo preclinical model. Our engineered Fc regions offer a means for improving the next generation of therapeutic antibodies and have the potential to broaden the diversity of antigens that can be targeted for antibody-based tumor therapy.

Alemtuzumab↗
PubMed2000

Different types of FCgamma-receptors are involved in anti-Lewis Y antibody induced effector functions in vitro.

Stimulation of monocytes by interaction of monoclonal antibodies (mAbs) with Fc gamma receptors (FcgammaRs) results in the activation of various monocyte effector functions. In the present investigation we show that the anti-Lewis Y (LeY) anti-tumour mAb ABL 364 and its mouse/human IgG1 chimaera induce both antibody-dependent cellular cytotoxicity (ADCC) and the release of tumour necrosis factor alpha (TNF-alpha) during mixed culture of monocytes with LeY+ SKBR5 breast cancer cells in vitro. Although anti-LeY mAb-mediated TNF-alpha release paralleled ADCC activity, cytokine release required a higher concentration of sensitizing mAb than the induction of cytolysis. The determination of the FcgammaR classes involved in the induction of the distinct effector functions showed that anti-LeY mAb-induced cytolysis was triggered by interaction between anti-LeY mAbs and FcgammaRI. In contrast, mAb-induced TNF-alpha release mainly depended on the activation of monocyte FcgammaRII. Neutralization of TNF-alpha showed no influence on monocyte ADCC activity towards SKBR5 target cells. Our data indicate an independent regulation of anti-LeY mAb induced effector functions of ADCC and TNF-alpha release which seemed to be triggered by activation of different types of FcgammaR.

Animals↗
PubMed1988

Isotypic restriction of the antibody response to human immunodeficiency virus.

HIV-infected individuals progress toward AIDS despite the early elicitation of a specific immune response. Analysis of the isotypic distribution of HIV-specific antibodies appears of special interest for two reasons: first, isotypic diversity is partly under the control of antigen-specific T-helper cells, the very cells infected by HIV; second, isotype determines antibody functions, effector (neutralization, antibody-dependent complement, or cell-mediated cytotoxicity) as well as blocking functions. We have investigated by Western blot analysis the isotypic profile of the antibody response to HIV structural proteins (env, gag, pol) and to the nonstructural protein F (3' orf), which is absent from the virion and might primarily target infected cells. In 115 asymptomatic individuals, infected by sexual contact (homosexual men) or intravenously (hemophiliacs), the response to gag-products was polyisotypic, including IgM, IgG1, IgG3 and IgA; the response to F was more restricted (IgM, IgG1, IgA) and the response to env strikingly restricted to the IgG1 isotype, suggesting different regulatory mechanisms in the B-cell response to these proteins. The isotypic distribution was also influenced by the route of infection, IgG4 and IgE (gag-specific) being exclusively elicited in the hemophiliac group. Finally, observations of potential diagnostic interest were made in a limited number of at-risk individuals; these included the presence of gag- and pol-specific IgM or IgA in the absence of any HIV-specific IgG isotypes; and the presence of gag- and F-specific antibodies in the absence of env-specific antibodies, suggesting the early occurrence of both isotypic and antigenic selection mechanisms during the course of HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed2006

Comparison of biological activity among nonfucosylated therapeutic IgG1 antibodies with three different N-linked Fc oligosaccharides: the high-mannose, hybrid, and complex types.

The structure of asparagine-linked oligosaccharides attached to the antibody constant region (Fc) of human immunoglobulin G1 (IgG1) has been shown to affect the pharmacokinetics and antibody effector functions of antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). However, it is still unclear how differences in the N-linked oligosaccharide structures impact the biological activities of antibodies, especially those lacking core fucose. Here, we succeeded in generating core fucose-lacking human IgG1 antibodies with three different N-linked Fc oligosaccharides, namely, a high-mannose, hybrid, and complex type, using the same producing clone, and compared their activities. Cultivation of an alpha-1,6-fucosyltransferase (FUT8) knockout Chinese hamster ovary cell line in the presence or absence of a glycosidase inhibitor (either swainsonine or kifunensine) yielded antibody production of each of the three types without contamination by the others. Two of three types of nonnaturally occurring atypical oligosaccharide IgG1, except the complex type, reduced the affinity for both human lymphocyte receptor IIIa (FcgammaRIIIa) and the C1q component of the complement, resulting in reduction of ADCC and CDC. The bulky structure of the nonreducing end of N-linked Fc oligosaccharides is considered to contribute the CDC change, whereas the structural change in the reducing end, i.e. the removal of core fucose, causes ADCC enhancement through improved FcgammaRIIIa binding. In the pharmacokinetic profile, although no significant difference of human neonatal Fc receptor (FcRn)-binding affinity was observed among the three types, the complex type showed longer serum half-lives than the other types irrespective of core fucosylation in mice, which also suggests the contribution of the nonreducing end structure. The present study provides basic information on the effects of core fucose-lacking N-linked Fc oligosaccharides on antibody biological activities.

Animals↗