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F A Nardella

Publications and source records attributed to F A Nardella.

At least 19 recordsLinked to original sources
PubMed1989

The Fc binding site for streptococcal protein G is in the C gamma 2-C gamma 3 interface region of IgG and is related to the sites that bind staphylococcal protein A and human rheumatoid factors.

The isolated 35 kDa fragment of protein G obtained by papain digestion of group G streptococci was found to bind solid phase intact IgG, Fc (2C gamma 2 + 2C gamma 3 domains), F(ab')2 and F(acb)2 (F(ab')2 + 2C gamma 2 domains) fragments but not pFc' (2C gamma 3 domains) fragments. The level of binding to rabbit F(acb)2 and rabbit F(ab')2 fragments was similar. Protein G binding to solid phase Fc fragments was inhibited by IgG, Fc, staphylococcal protein A and its monovalent fragment D, but was enhanced by F(ab')2 fragments. Chemical modification of tyrosine but not histidine residues of IgG abrogated its ability to inhibit the binding of protein G to solid phase Fc fragments. Protein G was found to strongly inhibit the binding of a monoclonal and a polyclonal human rheumatoid factor to IgG. These findings indicate that protein G binds with separate sites to the Fc and F(ab')2 fragments of IgG, that the interaction with the Fc fragment occurs at the C gamma 2-C gamma 3 domain interface region and that tyrosine but not histidine residues in this area are likely involved. The relationship of the Fc fragment-binding site specificity of protein G to that of other microbial IgG binding proteins and human rheumatoid factors is discussed.

Animals↗
PubMed1989

Herpes simplex type 1-induced Fc receptor binds to the Cgamma2-Cgamma3 interface region of IgG in the area that binds staphylococcal protein A.

The binding site of immunoglobulin G (IgG) to herpes simplex virus (HSV) type 1-induced Fc receptor was investigated using human IgG Fc intermediate (Fc(i)) fragments, fragment D of staphylococcal protein A (SPA) and chemically modified human IgG. Human IgG Fc(i) fragment composed of one Cgamma2 and two Cgamma3 domains, bound strongly to HSV-1-infected cells. Fragment D, a monovalent subunit of SPA, inhibited the binding of radiolabelled human IgG Fc fragments to the HSV Fc receptor. Reductively methylated human IgG reacted equally well to HSV-infected cells, as did chemically unmodified IgG in contrast to N-acetylimidazole-modified and diethylpyrocarbonate-modifed human IgG, which were unreactive. These results suggest a similar binding site on human IgG for SPA and the HSV-1 Fc receptor with involvement of the amino acid residues Tyr and His but not Lys. The similarities of binding sites on the IgG molecule for the HSV-1 Fc receptor and rheumatoid factors (RF) may be important for understanding the mechanism of RF production in rheumatoid arthritis or other disease states.

Animals↗
PubMed1988

Antigenic specificities of human monoclonal and polyclonal IgM rheumatoid factors. The C gamma 2-C gamma 3 interface region contains the major determinants.

The binding site specificity of 12 monoclonal and 11 polyclonal IgM rheumatoid factors (RF) isolated from human plasma or serum has been studied. All IgM RF bound best to sites on IgG and intact Fc. The monoclonal IgM RF did not bind at all to fragments lacking the C gamma 2 or C gamma 3 domains. In contrast, low level binding to the pFc' fragment, composed of the C gamma 3 domain, was seen with seven IgM RF, mainly from patients with rheumatoid arthritis (RA). IgG1 binding appeared to be a requisite specificity of all human IgM RF. IgM RF binding to IgG3 subclass was common among the monoclonal IgM RF. Most RA polyclonal IgM RF but only 2 of the monoclonal IgM RF possessed the IgG1, 2 and 4 binding pattern. Monoclonal IgM RF which bound best to histidine-modified IgG also bound well to IgG3. The 7-kDa fragment D of staphylococcal protein A inhibited the IgG binding of most monoclonal and to a lesser degree polyclonal IgM RF. Thus, the results indicate that the C gamma 2-C gamma 3 interface region of IgG contains the predominant determinants for monoclonal and polyclonal IgM RF. For some monoclonal IgM RF the binding site, even though at the interface of the C gamma 2 and C gamma 3 domains, is not the staphylococcal protein A site. Furthermore, polyclonal IgM RF possess specificities not encountered among the monoclonal IgM RF. These specificities may have special

Animals↗
PubMed1988

Absence of auto-antiidiotypic activity between the IgM and IgG fractions of human mixed cryoglobulins.

Experimental animal models and observations in humans suggest that levels of Id and auto-anti-Id fluctuate reciprocally after Ag stimulation. In human monoclonal B cell disorders, however, the co-existence of paraprotein Id and its auto-anti-Id has been described in essential mixed cryoglobulinemia and in association with acquired C1 inhibitor deficiency. Because the majority of cryoglobulin IgM possess rheumatoid factor activity and thus bind the Fc region of IgG, we examined potential idiotypic interactions between cryoglobulin IgM and F(ab')2 fragments of autologous cryoglobulin IgG fractions. A rabbit antibody to the pepsin agglutinator site of human F(ab')2 was used as detection reagent. By recognizing epitopes exposed on F(ab')2 after the removal of Fc determinants by pepsin digestion, this reagent eliminates the detection of contaminating intact IgG. In a sensitive assay, we were unable to detect idiotypic interactions between the separated IgM and pepsin-digested IgG fractions of 10 mixed cryoglobulins. On the basis of these results, we suggest that in mixed cryoglobulinemia, the coexistence of paraprotein Id and its auto-anti-Id is unlikely.

Antibodies, Anti-Idiotypic↗
PubMed1988

Fc epitopes for human rheumatoid factors and the relationships of rheumatoid factors to the Fc binding proteins of microorganisms.

Work from our laboratories has shown that the major antigenic determinants for rheumatoid factors (RFs) are in the C gamma 2-C gamma 3 interface region of IgG in the same area that binds staphylococcal protein A (SPA). Furthermore, the Fc binding proteins of groups A, C and G streptococci as well as the Fc binding proteins induced on cell surfaces by herpes simplex virus type I also bind to the same area of IgG. These binding site similarities between RFs and the microbial Fc binding proteins suggested conformational similarities between the RF antigen combining regions and the Fc binding regions of the microbial proteins. This hypothesis was supported by the observation that antibodies to SPA bind to the antigen combining regions of most RFs as well as to the Fc binding region of the T15 group A streptococcal Fc binding protein. These findings indicate that RFs bear the conformational internal image of these microbial proteins and suggest that RFs could arise as antibodies to the idiotypic determinants on antibodies to microbial Fc binding proteins. Alternatively, microbial Fc binding proteins could present IgG to the immune system in a way that renders specific areas of the C gamma 2-C gamma 3 interface region immunogenic. These relationships between RFs and microbial Fc binding proteins may prove to be important for our understanding of the generation of RFs in rheumatoid arthritis.

Binding Sites↗
PubMed1987

Human rheumatoid factors bear the internal image of the Fc binding region of staphylococcal protein A.

The binding specificity of rheumatoid factors (RFs) to human Fc resembles that of some microbial Fc-binding proteins, suggesting conformational similarities in their Fc-binding regions. Using polyclonal chicken antibodies against SPA, we have detected a crossreactive determinant shared by human RFs from different individuals, but not by non-RF IgM and IgG. Chicken anti-SPA was shown to bind to 18 of 19 IgM RFs and 2 of 2 IgG RFs isolated from different individuals. This binding was inhibitable with SPA, fragment D of SPA, human IgG, and Fc fragment of IgG. The binding site for RF was located on the Fab' fragment of chicken anti-SPA. The antigenic mimicry of RFs by a protein of microbial origin suggests that the immune response to infectious agents could induce or modulate RF production through an internal image autoantiidiotype mechanism.

Animals↗
PubMed1987

Rheumatoid factors from patients with rheumatoid arthritis possess private repertoires of idiotypes.

Considerable interest has focused on idiotypic cross-reactivity among antibody molecules. Cross-reactive idiotypes (Id) on monoclonal and polyclonal rheumatoid factors (RF) have been found frequently. Sufficient attention has not been directed, however, to the proportion of RF exhibiting the cross-reactivity, leaving the impression of extensive RF cross-reactivity when, in fact, this might represent a small minority of total RF molecules in a given individual. We have examined the polyclonal RF from patients with rheumatoid arthritis (RA) for cross-reactive Id in three different assays and with different Id-anti-Id systems. First, a sensitive liquid-phase radioimmunoassay was used in which panels of sera were tested for inhibition of different, idiotypically unrelated, Id-anti-Id interactions. When compared with normal sera, some of the sera from patients with RA caused minimal inhibition of Id-anti-Id interactions. None, however, caused marked inhibition of any Id-anti-Id system. Secondly, the panels of sera were also tested in a direct binding ELISA to detect partially cross-reactive Id that may not have been identified in the inhibition radioimmunoassay without differing results. Finally, results similar to the autologous Id-anti-Id inhibition assay were also found when the panels of RA sera were tested in two nonautologous Id-anti-Id systems, in which the anti-Id reacted with other than their own Id. These studies indicate that although cross-reactivity with some RF of an individual's total RF population may be seen frequently, an individual's repertoire of RF is itself private, quite diverse, and unique to that individual.

Antibodies, Anti-Idiotypic↗
PubMed1987

T15 group A streptococcal Fc receptor binds to the same location on IgG as staphylococcal protein A and IgG rheumatoid factors.

Previous work has shown that IgG rheumatoid factors (RF) bind to the C gamma 2-C gamma 3 interface region of human IgG in the same area that binds staphylococcal protein A (SPA). Group A, C, and G strains of Streptococci possess Fc receptors that bind to IgG but not to fragments containing only the C gamma 2 or C gamma 3 domains. This work describes the binding site location on human IgG for the binding of the isolated Fc receptor from the T15 strain of a Group A streptococcus and its relationship to the site that binds SPA and the IgG RF. The isolated T15 Fc receptor (T15) with a molecular mass of 29.5 kD inhibited the binding of IgG RF to IgG. The binding of T15 itself to IgG was strongly inhibited by SPA (42.0 kD) and its monovalent fragment D (7 kD). Human IgG fragments consisting of the C gamma 3 domains did not inhibit the binding of T15 to IgG, whereas those with both domains were effective inhibitors. T15 did not bind to rabbit IgG fragments consisting of either the C gamma 2 or C gamma 3 domains, but did bind to those with both domains. An IgG3 myeloma protein was a poor inhibitor and has been shown to bind poorly to the IgG RF. Most IgG3 myeloma proteins did not bind to SPA. The substitution of Arg and Phe for His 435 and Tyr 436 is responsible for the poor binding of IgG3 to SPA and to the IgG RF. Chemical modification of His or Tyr on IgG reduced its ability to inhibit the binding of T15 to IgG. Reversal of the chemical modifications with hydroxylamine resulted in near complete restoration of inhibitory capacity. This information, collectively, coupled with the known positions in space of the His and Tyr residues in the C gamma 2-C gamma 3 interface region, verified that both His 435 and Tyr 436, and possibly His 310 and 433, are involved. These residues are also involved in binding SPA and the IgG RF. These data therefore indicate that the T15 Group A Streptococcal Fc receptor binds to the same location on the Fc of IgG as SPA and the IgG RF. The biologic relevance of these similarities between bacterial cell wall Fc receptors and IgG RF are not yet apparent, but suggest that RF could bear the internal image of these bacterial structures.

Animals↗
PubMed1987

Identification of the site on IgG Fc for interaction with streptococci of groups A, C and G.

The interaction between living groups A, C and G streptococci and IgG Fc was studied using human IgG, IgG Fc and IgG Fc-intermediate (Fci) fragments, chemically modified human IgG and fragment D of staphylococcal protein A (SPA). Diethylpyrocarbonate modification of His or N-acetylimidazole modification of Tyr of human IgG resulted in the loss of its capacity to inhibit the binding of radiolabelled human IgG Fc to the group A streptococci types M1 and M55, and to the group C strain SC-1, indicating that the amino acids His and Tyr are involved in the binding. Lys seems not to participate in the binding of IgG to these bacteria, however, since reductive methylation of Lys did not reduce its inhibitory capacity. Fragment D of SPA also inhibited the binding of radiolabelled human IgG Fc to strains M1, M55 and SC-1. We have previously shown that these bacteria do not bind to IgG fragments consisting of only the C gamma 2 or C gamma 3 domains. On the basis of these results, and the known relative positions in space of the His and Tyr residues on IgG Fc, it is speculated whether streptococci with IgG Fc receptors, like SPA and rheumatoid factors, interact with IgG in the interface between the C gamma 2 and C gamma 3 domains and involve His 435 and one or more of Tyr 436, His 433 and His 310. The similarities in binding sites on IgG for RFs and these bacterial Fc binding proteins suggest structural similarities between them that may be relevant to the production of rheumatoid factors in rheumatoid arthritis.

Antigen-Antibody Reactions↗
PubMed1986

Minimal spinal hyperostosis with low-dose isotretinoin therapy.

Skeletal abnormalities have been reported on numerous occasions in patients who have received high doses of vitamin A and its derivatives. Recently, a new derivative, isotretinoin (Accutane, Hoffman-LaRoche, Inc.), has become available for the treatment of cystic acne. Ninety-six patients treated for a minimum of four months with low doses of this drug at two University centers have shown overall good to excellent clinical responses. However, ten of these patients have developed small pointed excrescences on the anterior margins of cervical, thoracic, or lumbar vertebral bodies. The findings are of unknown clinical significance but show some similarities to the spinal findings in DISH syndrome. Follow-up studies will be obtained, but, at the present time, the drug still can be recommended for patients who have severe cystic acne because of the excellent clinical response.

Acne Vulgaris↗
PubMed1986

Interaction between herpes simplex type 1-induced Fc receptor and human and rabbit immunoglobulin G (IgG) domains.

Cells infected with herpes simplex virus type 1 (HSV-1) express a cell surface receptor able to bind to the Fc region of immunoglobulin G (IgG). The ability of HSV-1-infected cells to bind 125I-labelled human and rabbit IgG and IgG fragments was studied to localize the site of interaction to the C gamma 2 or C gamma 3 domains of IgG. 125I-labelled IgG and IgG Fc fragments consisting of C gamma 2 and C gamma 3 domains bound strongly to HSV-infected cells and did not bind to uninfected cells. In contrast, 125I-labelled F(ab')2, Facb [consisting of F(ab')2 and C gamma 2 domains] and pFc' (consisting of C gamma 3 domains) fragments did not bind to any of these cells. Unlabelled IgG and IgG Fc fragments inhibited the interaction between 125I-labelled rabbit IgG Fc and the HSV Fc receptor, whereas F(ab')2, Facb and pFc' fragments failed to inhibit this interaction. These data indicate that the HSV Fc receptor requires both the C gamma 2 and C gamma 3 domains for interaction with the IgG molecule analogous to the known interaction of protein A of Staphylococcus aureus, the Fc binding proteins of Group A, C and G streptococci, and certain human rheumatoid factors.

Animals↗
PubMed1986

Interaction between streptococcal IgG Fc receptors and human and rabbit IgG domains.

Groups A, C and G streptococci were tested for their ability to bind 125I-labelled fragments of human and rabbit IgG in order to localize their sites of interaction with IgG domains. Among the Group A streptococci, strains with IgG Fc receptors bound 85% of the added IgG Fc fragments in the test systems, whereas these strains showed practically no reactivity with F(ab')2, Facb (F(ab')2 + C gamma 2 domains) or pFc' (C gamma 3 domains). The Group C and Group G strains bound 48-100% of IgG Fc, but could also bind up to 36% of the added F(ab')2 in accordance with a previously described 'alternative' Fab reactivity. However, unlabelled IgG F(ab')2 or Facb showed no, or only slight, inhibitory capacity for the binding of 125I-labelled IgG Fc to the C and G strains. Collectively, these results indicate that Groups A, C and G streptococci require both the C gamma 2 and C gamma 3 domains for interaction with IgG, and most probably also bind in the interface region between the C gamma 2 and C gamma 3 domains as has been shown for staphylococcal protein A.

Animals↗
PubMed1985

IgG rheumatoid factors and staphylococcal protein A bind to a common molecular site on IgG.

The antigenic determinant on the Fc region of human IgG for two IgG rheumatoid factors (IgG-RF) from patients with rheumatoid arthritis were investigated in detail. The RF did not interact with IgG fragments that contained the C gamma 2 or C gamma 3 region alone, but required the presence of both regions for binding. The RF binding to solid-phase IgG were poorly inhibited by the IgG3 subclass and strongly inhibited by staphylococcal protein A (SPA) (42 kD), and fragment D of SPA (7 kD), indicating that the binding site is most likely the same as the Ga antigenic determinant described for IgM-RF, and is in the same location as the site on IgG that binds SPA. pH titration studies of the RF binding to IgG indicated the involvement of histidine and lysine or tyrosine side chains. Chemical modification studies showed the histidines were involved on the Fc side of the interactions, and tyrosines were involved on both the antigenic and antibody sides of the interactions. Lysines were not involved. The above information, and the knowledge of the number and position in space of the amino acid residues involved in the C gamma 2-C gamma 3 interface region of IgG, the binding site for SPA, and the amino acid substitutions in IgG3 that account for its inability to bind protein A, allowed the identification of the site on IgG that bind IgG-RF. This binding site involves some of the same amino acid side chains, His 435, Tyr 436, and one or both His 433 and 310, and is in the same location as the site that binds SPA. The same site is likely to be a common antigenic determinant for other RF. Furthermore, the described molecular mimicry suggests a biological relationship between bacterial Fc-binding proteins and the production of RF in rheumatoid arthritis.

Arthritis, Rheumatoid↗
PubMed1985

Cyanogen bromide cleaves Fc fragments of pooled human IgG at both methionine and tryptophan residues.

An attempt was made to obtain fragments containing the C gamma 2 region by selectively cleaving human Fc fragments prepared from pooled IgG at Met residues using cyanogen bromide. Based on the known locations of Met residues in the Fc regions of human IgG subclasses, fragments between Met 252 and 358, comprising the C gamma 2 domains, were expected from IgGl Gm -1, IgG2, IgG3 and IgG4. Greater fragmentation of the Fc fragments occurred, however, than was predicted. Automated N-terminal sequencing identified five major points (Trp 381, 313 and 277, and Met 397 and 252) and two minor points of cleavage (Met 428 and Trp 417). The majority of cleavage points occurred at Trp rather than Met. Furthermore, cleavage at Met 358, necessary to produce C gamma 2 domains, was not detected. Control experiments verified the integrity of the Fc fragments handled in exactly the same manner without cyanogen bromide exposure and the ability of the same cyanogen bromide preparation to produce the expected cleavages at Met of sperm whale apomyoglobin without fragmentation at Trp. Cleavage at Met 358 did not occur presumably because of the difficulty associated with cyanogen bromide cleavage at Met-Thr peptide bonds. Cleavage at Trp probably occurred by way of halogen promoted oxidation of the indole nucleus with resultant peptide bond fissure. These observations show that cyanogen bromide cleavage of pooled human Fc fragments is not selective for Met, but also cleaves at Trp residues. The resultant fragmentation of the C gamma 2 region coupled with the inability to make the required cleavage at the 358-359 Met-Thr bond resulted in the inability to produce fragments comprising the C gamma 2 domains. The reasons for the selective cleavage at Met in some proteins and the cleavage at both Trp and Met in others are not known.

Chemical Phenomena↗
PubMed1985

Fc intermediate (Fci), a papain-generated fragment of human IgG, intermediate in charge, molecular weight and cleavage between the Fc and Fc' fragments of IgG.

Fc intermediate (Fci) is a papain-generated fragment of human IgG which is intermediate in charge, mol. wt and state of cleavage between the Fc and Fc' fragments of IgG. It is composed of two polypeptide chains of unequal mol. wt held together by non-covalent bonds between the C gamma 3 regions. The larger polypeptide chain has both a C gamma 2 and C gamma 3 domain and its N-terminus is at Leu 235 (60%) and Leu 234 (40%) (IgGl Eu numbering). The smaller polypeptide chain is composed of a C gamma 3 domain with its N-terminus at Gly 341. The carboxy-termini obtained by carboxypeptidase digestion and by a computer program which determined the most probable sequences by fitting the amino acid compositions to the sequence of IgG Eu Fc were heterogeneous involving residues 440-446 for the large polypeptide chain and 429-436 for the small one. The calculated mol. wt of the large polypeptide chain was 26,183, assuming the N-terminus at Leu 234 and C-terminus at 446 and including the carbohydrate moiety. The calculated mol. wt for the small polypeptide chain was 10,682, with the N-terminus at 341 and assuming the C-terminus at 434, for a combined mol. wt of 36,865 for the Fci fragment. Sedimentation equilibrium ultracentrifugation of Fci under non-dissociating conditions showed an Mn of 36,200 +/- 1200, an Mw of 36,400 +/- 600 and an Mz of 37,000 +/- 300 g/mole. The best yields of Fc were obtained with a 6-hr digestion and the best yields of Fcl and Fc' were obtained with digestion for 18 hr in phosphate buffer. Digestion in Tris buffer for 18 hr gave results similar to the 18-hr digestion in phosphate buffer except the yields of Fc' were less. This fragment may be useful for exploring biological functions of human IgG Fc. In addition, some Fc fragments obtained by papain digestion of human IgG either in phosphate or Tris buffer are not covalently bonded and are probably cleaved on the carboxy-terminal side of the interchain disulfide bonds at Leu 234 or Leu 235, the N-termini for the large polypeptide chain of Fci. This indicates that, if disulfide bonded Fc fragments are needed, gel filtration under dissociating conditions will be necessary to remove non-covalently bonded Fc.

Amino Acid Sequence↗
PubMed1985

IgG rheumatoid factors and self-association of these antibodies.

IgG RFs are unique antibodies since they form immune complexes by self-association without the presence of separate antigen molecules. These immune complexes can drive inflammation by complement activation and by interaction with monocytes. Plasma cells in the synovial tissues of patients with RA synthesize IgG RFs and other rheumatoid factors. The reason for the accumulation of these cells in the synovium has not been elucidated. The detection and quantitation of IgG RFs has been difficult owing to the unique nature of these antibodies. The methods for this purpose, however, have improved. In patients with RA the presence of high levels of IgG RFs in serum is associated with clinical evidence of vasculitis. The quantitation of IgG RFs in serum of patients has not yet been established as a diagnostic or prognostic tool. Available evidence, however, suggests that these antibodies have a significant role in the pathogenesis of rheumatoid arthritis.

Animals↗
PubMed1985

Competition between antigen and anti-idiotypes for rheumatoid factors.

Many idiotypic determinants on antibody molecules are thought to be located at the antigen binding site, and therefore the interaction between idiotype (Id) and anti-idiotype (anti-Id) is expected to be inhibited by the antigen. We describe two IgG and one IgM rheumatoid factors whose interactions with their respective anti-Id could only be partially inhibited by very large amounts of antigen, i.e., normal IgG. The anti-Id, however, readily inhibited the binding of their respective rheumatoid factors to IgG. The differences in interaction energies resulted in failure of antigen to readily block the Id-anti-Id interaction, and did not mean that the Id was not at the antigen combining site. The association constants for the Id-anti-Id interactions varied from 1.3 to 14.8 X 10(7) M-1, whereas the strength of the rheumatoid factor antigen bond is on the order of 10(5) M-1 for interaction with monomeric IgG. In addition, the anti-Id were able to remove rheumatoid factors that were bound to solid phase IgG, indicating that anti-Id have the potential for disrupting the immune complexes formed by antigen and antibody.

Animals↗