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PubMed1994

Purification of antibody-antigen complexes containing recombinant SIV proteins: comparison of antigen and antibody-antigen complexes for immune priming.

This paper describes a general procedure for the two-step purification of recombinant proteins as antibody-antigen complexes in which there is no uncomplexed antibody or antigen. In this way, immune complexes containing the p17, p27, vpr and vpx proteins of simian immunodeficiency virus (SIV) have been purified. Antibody-antigen complexes are more immunogenic than antigen when administered either alone or with alum. The significance of the work is that this general method could be modified for the manufacture of immune complexes for incorporation into multivalent vaccines.

Animals↗

PubMed1988

The bovine pro-carboxypeptidase A-S6 ternary complex: a rare case of a secreted protein complex.

Up to now, a non-covalent ternary complex in which the pro-carboxypeptidase A (subunit I) is associated to two functionally different proteins (subunits II and III) has only been found in the pancreas of ruminant species. In the other species studied so far, the pro-carboxypeptidase A is secreted either as a monomer or as a binary association with a functionally different protein. Subunit I is the immediate precursor of carboxypeptidase A. Subunit II is a chymotrypsinogen of the C-type, involved, like subunit I, in the degradation of proteins and peptides. Although closely related to the pancreatic serine endopeptidases, subunit III appears to be devoid of any specific enzymatic activity. Information about the spatial organization of the subunits in the ternary complex has been deduced from the sequential dissociation of the complex. In contrast to the mechanism of activation of subunits I and II, which is independent of their aggregation state, the catalytic properties of the resulting enzymes are sensitive to their aggregation state. Moreover, the structural basis of inactivity of subunit III as well as the physiological role of the ternary complex are also discussed in this review.

Amino Acid Sequence↗

PubMed1998

Mechanism of ubiquinol oxidation by the cytochrome bc1 complex: pre-steady-state kinetics of cytochrome bc1 complexes containing site-directed mutants of the Rieske iron-sulfur protein.

To facilitate characterization of mutated cytochrome bc1 complexes in S. cerevisiae we have developed a new approach using a rapid scanning monochromator to examine pre-steady-state reduction of the enzyme with menaquinol. The RSM records optical spectra of cytochromes b and c1 at 1-ms intervals after a dead time of 2 ms, and menaquinol fully reduces both cytochromes bH and c1 and a portion of cytochrome bL. The rapid-mixing, rapid-scanning monochromator methodology obviates limitations inherent in previous rapid kinetics methods and permits measurements of rates exceeding 200 s-1. To document the validity of this methodology we have examined the reduction kinetics of the cytochrome bc1 complexes from wild-type yeast and yeast that lack ubiquinone. The results establish that menaquinol reacts via the Q cycle pathway both in the presence and absence of ubiquinone. From analyzing bc1 complexes containing Rieske proteins in which the midpoint potential of the iron-sulfur cluster has been altered from +280 to +105 mV, we propose a mechanism in which the protonated quinol displaces a proton from the imidazole nitrogen of one of the histidines that is a ligand to the iron-sulfur cluster and forms a quinol-imidazolate complex that is the electron donor to the redox active iron.

Animals↗

PubMed2000

Trafficking of major histocompatibility complex class II molecules in human B-lymphoblasts deficient in the AP-3 adaptor complex.

The major histocompatibility complex class II subunits (MHC-II) alpha and beta assemble with the invariant chain (Ii) in the endoplasmic reticulum and are transported to endosomal-lysosomal organelles known as MHC class II compartments (MIICs). Although it has been shown that two dileucine-based signals in the cytosolic tail of Ii, as well as a dileucine-based signal in the tail of the beta chain mediate sorting to MIICs, the molecular mechanisms by which alphabetaIi complexes are sorted have yet to be resolved fully. The AP-3 adaptor complex stands out as a particularly good candidate for mediating this targeting because: (i) it has a proven role in the trafficking of membrane proteins to lysosome-related organelles; and (ii) it has the ability to interact with dileucine-based signals in vitro. To investigate the potential role of AP-3 in transport of MHC-II to MIICs, we have examined MHC-II trafficking in human B-lymphoblast lines from patients with Hermansky-Pudlak syndrome type 2 (HPS-2), which are deficient in the AP-3 complex. Pulse-chase analyses revealed no significant alteration in the kinetics of synthesis and degradation of either MHC-II subunits or Ii. Moreover, we observed neither impairment of the formation of compact SDS-resistant alphabeta dimers, nor delay in the appearance of a conformational epitope indicative of a mature, Ii-free alphabeta dimer. Finally, we demonstrated that in HPS-2 patients' cells, there was no delay in the expression of the alphabeta dimers on the cell surface. Thus, AP-3 does not seem to be essential for normal trafficking of MHC-II. These findings have important implications for HPS-2 patients, because they suggest that the recurrent bacterial infections suffered by these patients are not likely due to impaired antigen processing and presentation by MHC-II.

Adaptor Protein Complex alpha Subunits↗

PubMed2005

Electron spin-lattice relaxation of the S0 state of the oxygen-evolving complex in photosystem II and of dinuclear manganese model complexes.

The temperature dependence of the electron spin-lattice relaxation time T1 was measured for the S0 state of the oxygen-evolving complex (OEC) in photosystem II and for two dinuclear manganese model complexes by pulse EPR using the inversion-recovery method. For [Mn(III)Mn(IV)(mu-O)2 bipy4]ClO4, the Raman relaxation process dominates at temperatures below 50 K. In contrast, Orbach type relaxation was found for [Mn(II)Mn(III)(mu-OH)(mu-piv)2(Me3 tacn)2](ClO4)2 between 4.3 and 9 K. For the latter complex, an energy separation of 24.7-28.0 cm(-1) between the ground and the first excited electronic state was determined. In the S0 state of photosystem II, the T1 relaxation times were measured in the range of 4.3-6.5 K. A comparison with the relaxation data (rate and pre-exponential factor) of the two model complexes and of the S2 state of photosystem II indicates that the Orbach relaxation process is dominant for the S0 state and that its first excited state lies 21.7 +/- 0.4 cm(-1) above its ground state. The results are discussed with respect to the structure of the OEC in photosystem II.

Electron Spin Resonance Spectroscopy↗

PubMed1995

Crystal structure of an H-2Kb-ovalbumin peptide complex reveals the interplay of primary and secondary anchor positions in the major histocompatibility complex binding groove.

Sequence analysis of peptides naturally presented by major histocompatibility complex (MHC) class I molecules has revealed allele-specific motifs in which the peptide length and the residues observed at certain positions are restricted. Nevertheless, peptides containing the standard motif often fail to bind with high affinity or form physiologically stable complexes. Here we present the crystal structure of a well-characterized antigenic peptide from ovalbumin [OVA-8, ovalbumin-(257-264), SIINFEKL] in complex with the murine MHC class I H-2Kb molecule at 2.5-A resolution. Hydrophobic peptide residues Ile-P2 and Phe-P5 are packed closely together into binding pockets B and C, suggesting that the interplay of peptide anchor (P5) and secondary anchor (P2) residues can couple the preferred sequences at these positions. Comparison with the crystal structures of H-2Kb in complex with peptides VSV-8 (RGYVYQGL) and SEV-9 (FAPGNYPAL), where a Tyr residue is used as the C pocket anchor, reveals that the conserved water molecule that binds into the B pocket and mediates hydrogen bonding from the buried anchor hydroxyl group could not be likewise positioned if the P2 side chain were of significant size. Based on this structural evidence, H-2Kb has at least two submotifs: one with Tyr at P5 (or P6 for nonamer peptides) and a small residue at P2 (i.e., Ala or Gly) and another with Phe at P5 and a medium-sized hydrophobic residue at P2 (i.e., Ile). Deciphering of these secondary submotifs from both crystallographic and immunological studies of MHC peptide binding should increase the accuracy of T-cell epitope prediction.

Amino Acid Sequence↗

PubMed1997

The N terminus of the Qcr7 protein of the cytochrome bc1 complex is not essential for import into mitochondria in Saccharomyces cerevisiae but is essential for assembly of the complex.

Subunit 7 of the yeast cytochrome bc1 complex is encoded by the nuclear QCR7 gene and is essential for respiration. This protein does not contain a cleavable N-terminal mitochondrial targeting sequence, and it is not understood how the Qcr7 protein is imported into mitochondria and assembled into the complex. To test the role of the N terminus of the Qcr7 protein in mitochondrial import, assembly of the complex, and proton translocation, we inactivated the endogenous QCR7 gene and expressed mutated qcr7 genes capable of synthesizing proteins truncated by 7, 10, 14, and 20 residues (Qcr7p-delta7, Qcr7p-delta10, Qcr7p-delta14, and Qcr7p-delta20, respectively) from the N terminus. In addition, we studied two mutants containing Qcr7 proteins with point mutations in addition to a delta7 truncation, Qcr7p-delta7(D13V) and Qcr7p-delta7(R10K). All the mutant proteins with the exception of Qcr7p-delta10 were present in the mitochondria at 30 degrees C, although most at lower steady-state levels than the Qcr7p from the strain overexpressing wild type QCR7. The absence of the Qcr7p-delta10 may be the result of an unstable protein or a decrease in the efficiency of mitochondrial import due to its compromised amphipathic alpha-helix and the presence of a negative charge exposed at the N terminus. Cytochrome c reductase activities and the amounts of ATP synthesized were comparable with the wild type in the strain expressing Qcr7p-delta7. The strain expressing Qcr7p-delta7(R10K) had an identical phenotype to the one containing the Qcr7p-delta7, whereas strains expressing the Qcr7p-delta10, Qcr7p-delta14, Qcr7p-delta20, and Qcr7p-delta7(D13V) were all respiration-deficient. Examination of the steady-state levels of complex III subunits showed that core protein 2, cytochrome c1, the iron-sulfur protein, and the 11-kDa subunit are reduced in respiration-deficient mutant strains. Results from deletion analyses indicate that the N-terminal 20 residues (after Met-1) of the Qcr7 protein are not essential for import into mitochondria and that the N-terminal seven residues (after Met-1) are not involved in proton translocation. The results of this work show, however, that the N terminus of the Qcr7 protein is essential for the biosynthesis of ubiquinol-cytochrome c reductase.

Amino Acid Sequence↗

PubMed1997

Dihydrolipoamide dehydrogenase-binding protein of the human pyruvate dehydrogenase complex. DNA-derived amino acid sequence, expression, and reconstitution of the pyruvate dehydrogenase complex.

Protein X, recently renamed dihydrolipoamide dehydrogenase-binding protein (E3BP), is required for anchoring dihydrolipoamide dehydrogenase (E3) to the dihydrolipoamide transacetylase (E2) core of the pyruvate dehydrogenase complexes of eukaryotes. DNA and deduced protein sequences for E3BP of the human pyruvate dehydrogenase complex are reported here. With the exception of only a single lipoyl domain, the protein has a segmented multi-domain structure analogous to that of the E2 component of the complex. The protein has 46% amino acid sequence identity in its amino-terminal region with the second lipoyl domain of E2, 38% identity in its central region with the putative peripheral subunit-binding domain of E2, and 50% identity in its carboxyl-terminal region with the catalytic inner core domain of E2. The similarity in the latter domain stands in contrast to E3BP of Saccharomyces cerevisiae, which is quite different from its homologous transacetylase in this region. The putative catalytic site histidine residue present in the inner core domains of all dihydrolipoamide acyltransferases is replaced by a serine residue in human E3BP; thus, catalysis of coenzyme A acetylation by this protein is unlikely. Coexpression of cDNAs for E3BP and E2 resulted in the formation of an E2.E3BP subcomplex that spontaneously reconstituted the pyruvate dehydrogenase complex in the presence of native E3 and recombinant pyruvate decarboxylase (E1).

Amino Acid Sequence↗

PubMed2000

cAMP-dependent phosphorylation of the nuclear encoded 18-kDa (IP) subunit of respiratory complex I and activation of the complex in serum-starved mouse fibroblast cultures.

A study is presented on the in vivo effect of elevated cAMP levels induced by cholera toxin on the phosphorylation of subunits of the mitochondrial respiratory complexes and their activities in Balb/c 3T3 mouse fibroblast cultures. Treatment of serum-starved fibroblasts with cholera toxin promoted serine phosphorylation in the 18-kDa subunit of complex I. Phosphorylation of the 18-kDa subunit, in response to cholera toxin treatment of fibroblasts, was accompanied by a 2-3-fold enhancement of the rotenone-sensitive endogenous respiration of fibroblasts, of the rotenone-sensitive NADH oxidase, and of the NADH:ubiquinone oxidoreductase activity of complex I. Direct exposure of fibroblasts to dibutyryl cAMP resulted in an equally potent stimulation of the NADH:ubiquinone oxidoreductase activity. Stimulation of complex I activity and respiration with NAD-linked substrates were also observed upon short incubation of isolated fibroblast mitoplasts with dibutyryl cAMP and ATP, which also promoted phosphorylation of the 18-kDa subunit. These observations document an extension of cAMP-mediated intracellular signal transduction to the regulation of cellular respiration.

3T3 Cells↗

PubMed2001

Ubiquinol:cytochrome c oxidoreductase (complex III). Effect of inhibitors on cytochrome b reduction in submitochondrial particles and the role of ubiquinone in complex III.

Two sets of studies have been reported on the electron transfer pathway of complex III in bovine heart submitochondrial particles (SMP). 1) In the presence of myxothiazol, MOA-stilbene, stigmatellin, or of antimycin added to SMP pretreated with ascorbate and KCN to reduce the high potential components (iron-sulfur protein (ISP) and cytochrome c(1)) of complex III, addition of succinate reduced heme b(H) followed by a slow and partial reduction of heme b(L). Similar results were obtained when SMP were treated only with KCN or NaN(3), reagents that inhibit cytochrome oxidase, not complex III. The average initial rate of b(H) reduction under these conditions was about 25-30% of the rate of b reduction by succinate in antimycin-treated SMP, where both b(H) and b(L) were concomitantly reduced. These results have been discussed in relation to the Q-cycle hypothesis and the effect of the redox state of ISP/c(1) on cytochrome b reduction by succinate. 2) Reverse electron transfer from ISP reduced with ascorbate plus phenazine methosulfate to cytochrome b was studied in SMP, ubiquinone (Q)-depleted SMP containing </=0.06 mol of Q/mol of complex III, and Q-replenished SMP. The results showed that Q was not required for electron transfer from ISP to b, a reaction that was inhibited by antimycin (also by myxothiazol or MOA-stilbene as reported elsewhere). It was also shown that antimycin did not inhibit electron transfer from b (b(H)) to Q, in clear contrast to the assumption of the Q-cycle hypothesis regarding the site of antimycin inhibition.

Animals↗

PubMed2005

Reduction in the E2k subunit of the alpha-ketoglutarate dehydrogenase complex has effects independent of complex activity.

The activity of the alpha-ketoglutarate dehydrogenase complex (KGDHC) declines in brains of patients with several neurodegenerative diseases. KGDHC consists of multiple copies of E1k, E2k, and E3. E1k and E2k are unique to KGDHC and may have functions independent of the complex. The present study tested the consequences of different levels of diminished E2k mRNA on protein levels of the subunits, KGDHC activity, and physiological responses. Human embryonic kidney cells were stably transfected with an E2k sense or antisense expression vector. Sense control (E2k-mRNA-100) was compared with two clones in which the mRNA was reduced to 67% of control (E2k-mRNA-67) or to 30% of control (E2k-mRNA-30). The levels of the E2k protein in clones paralleled the reduction in mRNA, and E3 proteins were unaltered. Unexpectedly, the clone with the greatest reduction in E2k protein (E2k-mRNA-30) had a 40% increase in E1k protein. The activity of the complex was only 52% of normal in E2k-mRNA-67 clone, but was near normal (90%) in E2k-mRNA-30 clone. Subsequent experiments tested whether the physiological consequences of a reduction in E2k mRNA correlated more closely to E2k protein or to KGDHC activity. Growth rate, increased DCF-detectable reactive oxygen species, and cell death in response to added oxidant were proportional to E2k proteins, but not complex activity. These results were not predicted because subunits unique to KGDHC have never been manipulated in mammalian cells. These results suggest that in addition to its essential role in metabolism, the E2k component of KGDHC may have other novel roles.

Acyltransferases↗

PubMed2000

The interaction of the chaperonin tailless complex polypeptide 1 (TCP1) ring complex (TRiC) with ribosome-bound nascent chains examined using photo-cross-linking.

The eukaryotic chaperonin tailless complex polypeptide 1 (TCP1) ring complex (TRiC) (also called chaperonin containing TCP1 [CCT]) is a hetero-oligomeric complex that facilitates the proper folding of many cellular proteins. To better understand the manner in which TRiC interacts with newly translated polypeptides, we examined its association with nascent chains using a photo-cross-linking approach. To this end, a series of ribosome-bound nascent chains of defined lengths was prepared using truncated mRNAs. Photoactivatable probes were incorporated into these (35)S- labeled nascent chains during translation. Upon photolysis, TRiC was cross-linked to ribosome-bound polypeptides exposing at least 50-90 amino acids outside the ribosomal exit channel, indicating that the chaperonin associates with much shorter nascent chains than indicated by previous studies. Cross-links were observed for nascent chains of the cytosolic proteins actin, luciferase, and enolase, but not to ribosome-bound preprolactin. The pattern of cross-links became more complex as the nascent chain increased in length. These results suggest a chain length-dependent increase in the number of TRiC subunits involved in the interaction that is consistent with the idea that the substrate participates in subunit-specific contacts with the chaperonin. Both ribosome isolation by centrifugation through sucrose cushions and immunoprecipitation with anti-puromycin antibodies demonstrated that the photoadducts form on ribosome-bound polypeptides. Our results indicate that TRiC/CCT associates with the translating polypeptide shortly after it emerges from the ribosome and suggest a close association between the chaperonin and the translational apparatus.

Actins↗

PubMed1974

Renal deposition of soluble immune complexes in mice bearing B-16 melanoma. Characterization of complexes and relationship to tumor progress.

Histologic and immunofluorescence studies of the kidneys of mice bearing a progressive melanoma show a proliferative glomerulonephritis associated with immune complex deposition in the mesangium and along the glomerular basement membrane This immune complex disease is distinct from the age-associated disease of the C57BL/6J host strain and the complexes can be shown to consist of soluble tumor antigen and antitumor antibody. Furthermore, the intensity of IgG complex deposition correlates directly with tumor progress (size and metastases) and inversely with mononuclear leukocyte infiltration of the tumor. In vitro assays for lymphocyte cytotoxicity and humoral antibody were found to be less reliable indicators of tumor progress. The possible role of circulating soluble tumor antigen in modifying the immune response to tumors is discussed.

Age Factors↗

PubMed1989

Analysis of peptide binding patterns in different major histocompatibility complex/T cell receptor complexes using pigeon cytochrome c-specific T cell hybridomas. Evidence that a single peptide binds major histocompatibility complex in different conformations.

The interaction of TCR, antigen, and MHC complex has been analyzed using synthetic peptide antigens and a series of single amino acid-substituted analogues. Two similar antigens, mouse cytochrome c (mcyt c) and pigeon cytochrome c (pcyt c), elicit T cell responses in strains of mice bearing MHC class II Ek beta Ek alpha (B10.A), Eb beta Ek alpha [B10.A(5R)], and Es beta Ek alpha [B10.S(9R)]. The immunogenic regions of these antigens are located in the peptide sequence p88-104 for pcyt c and m88-103 for mcyt c. The limited T cell repertoire for these antigens is comprised of four groups of T cell phenotypes that have very few differences in their TCR gene make up. In this paper, we examine the diversity in their fine specificity for each of the antigens, m88-103 and p88-104, complexed with each of the I-Ek haplotypes. Epitopes, i.e., residues that interact with the TCR, and agretopes, i.e., residues in the MHC-binding site, were assigned for the two peptide antigens in the presence of APC bearing E beta kEk alpha, Eb beta Ek alpha, or Eb beta Ek alpha using T cell hybridomas of the phenotypes I, IIIa, and IV. From our results, we conclude that first, the substitution of any residue between 95 and 104 of the cytochrome c peptide changed the antigenic potency of the peptide for at least one of the hybridomas. Second, each T cell type has a different recognition pattern of epitopes and agretopes for a particular antigen-MHC complex, thus, ruling out a static model of T cell recognition, which assigns certain, invariant agretopic residues to the peptide by which it interacts with the MHC molecule independently of the TCR. Third, the same T cell hybridoma responded to the antigens differently when presented on various MHC molecules, implying that overall changes in the MHC groove, as displayed by the three haplotypes, may affect the efficiency in binding the peptide. Fourth, since most of the residues are used as epitopes by at least one of the T cell specificities, the peptide appears to be recognized in a different conformation by each T cell hybridoma phenotype; and, finally, the epitopic and agretopic residues do not segregate, for any one of the T cell specificities, in such a way that suggests they are recognized in a helical conformation. In summary, our results suggest that a single peptide may generate diversity in the T cell response by virtue of its conformational flexibility within the TCR-MHC-antigen complex.

Amino Acid Sequence↗

PubMed1978

Fc receptor bearing 'hairy cells' of leukaemic reticuloendotheliosis bind soluble antigen--antibody complexes and adhere to immobilized complexes, but fail to mediate antibody dependent cellular cytotoxicity.

The majority of hairy cells from three patients with leukaemic reticuloendotheliosis were adherent cells bearing surface immunoglobulin, complement receptors, and Fc receptors. Highly purified populations of malignant hairy cells, which readily bound soluble antigen-antibody complexes in suspension and were able to adhere to immobilized antigen-antibody complexes, were examined for their ability to mediate ADCC. Two patients with greater than 90% FcR positive cells failed to mediate ADCC. When initially examined, a third patient, with fewer malignant cells, demonstrated a less marked impairment of cytolysis. When reexamined at a later date, this patient had an increased number of hairy cells and concomitantly demonstrated more impaired ADCC effector cell activity. Absorption of surface immunoglobulin bearing cells onto plastic surfaces coated with goat anti-human immunoglobulin resulted in a complete depletion of FcR, sIg positive, hairy cells. The remaining nonadherent fraction, containing 5.5% FcR positive, sIg negative cells, was able to mediate ADCC as effectively as the normal controls. These results indicate that although FcR bearing hairy cells readily bind soluble antigen-antibody complexes and adhere to immobilized complexes, they were unable to mediate ADCC.

Adult↗

PubMed1988

Cytochrome b6f complex is required for phosphorylation of light-harvesting chlorophyll a/b complex II in chloroplast photosynthetic membranes.

The light-harvesting chlorophyll a/b complex (LHC II) and four photosystem II (PS II) core proteins (8.3, 32, 34 and 44 kDa) become phosphorylated in response to reduction of the intersystem electron transport chain of green plant chloroplasts. Previous studies indicated that reduction of the plastoquinone (PQ) pool is the key event in kinase activation. However, we show here that, unlike PS II proteins, LHC II is phosphorylated only when the cytochrome b6f complex is active. Two lines of evidence support this conclusion. (1) 2,5-Dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) and the 2,4-dinitrophenyl ether of iodonitrothymol (DNP-INT), which are known to block electron flow into the cytochrome complex, selectively inhibit LHC II phosphorylation in spinach thylakoids. (2) The hcf6 mutant of maize, which contains PQ but lacks the cytochrome b6f complex, phosphorylates the four PS II proteins but fails to phosphorylate LHC II in vivo or in vitro.

Benzoquinones↗

PubMed2006

Signaling within a coactivator complex: methylation of SRC-3/AIB1 is a molecular switch for complex disassembly.

Recent studies indicate that steroid receptor-mediated transcriptional initiation is a cyclical process involving multiple rounds of coactivator assembly and disassembly. Steroid receptor coactivator 3 (SRC-3) coactivator phosphorylation has been shown to regulate coactivator complex assembly, but the mechanisms by which coactivator disassembly is triggered are not well understood. In this study, we provide in vitro and in vivo evidence that members of the SRC coactivator family serve as substrates for the enzymatic coactivator coactivator-associated arginine methyltransferase 1 (CARM1). Methylation of SRC-3 was localized to an arginine in its CARM1 binding region and correlated with decreased estrogen receptor alpha-mediated transcription, as seen with both cell-based and in vitro transcription assays. Consistent with this finding, we demonstrated that methylation promotes dissociation of the SRC-3/CARM1 coactivator complex. Methylation of SRC-3 is regulated by estrogen signaling in MCF7 cells and serves as a molecular switch for disassembly of the SRC-3 transcriptional coactivator complex. We propose that CARM1 is a dual-function coactivator, as it not only activates transcription by modifying core histone tails but also terminates hormone signaling by disassembly of the coactivator complex.

Amino Acid Sequence↗

PubMed1986

Immune complexes in synovial fluid and serum from patients with disseminated gonococcal infection: evidence for local immune complex formation within the joint.

Twenty one patients with acute arthritis associated with disseminated gonococcal infection (DGI) were studied. Synovial fluid (SF) from 14 and serum from 15 (matched in eight) were assayed for the presence of immune complexes (IC) by the Raji cell immunofluorescent assay (Raji IFA) and the 125I-Clq polyethylene glycol (PEG) binding assay. Higher levels and frequency of IC were detected in the SF by both IC assays and these were associated with a significant increase in complexes containing IgM over serum (p less than 0.02). Complexes containing IgG were found predominantly in serum and were infrequent in SF (p less than 0.003). These data suggest that the arthritis of DGI may result from primary immune complex formation within the synovial cavity after local antibody synthesis within the synovium in response to gonococcal seeding.

Antigen-Antibody Complex↗