Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Immune complexes, prepared with monoclonal rat IgA antibodies directed against DNP, activate the alternative pathway of the complement system in rat serum. In this study, the interaction of these monoclonal IgA antibodies with the classical pathway of complement was investigated. Monoclonal polymeric IgA (p-IgA) was shown to inhibit the IgG2b-mediated classical pathway-dependent lysis of TNP-coated sheep red blood cells. In addition, the binding of C3 to solid phase IgG2b immune complexes was inhibited by p-IgA. Monoclonal monomeric IgA (m-IgA) was much less efficient in this respect. To further analyse the effect of p-IgA on the activation of the classical pathway by IgG2b immune complexes, the interaction of p-IgA with C1 was studied. It was found that p-IgA antibodies bind C1q. No species-specificity was observed, since both rat and human C1q were bound. Whereas binding of C1q in C1 to IgG2b resulted in activation of C1, binding to p-IgA did not. The binding of C1q to both p-IgA and IgG2b could be inhibited by monoclonal antibodies directed against the globular heads of C1q, but not by monoclonal antibodies directed against the collagen tail. The formation of insoluble p-IgA immune complexes was inhibited in the presence of rat serum or C1. These studies indicate that C1q binds to p-IgA by its globular heads, and thereby may modulate classical pathway-mediated reactions such as the inhibition of immune precipitate formation.
Mol Immunol 1990 Sep
PMID:Rat polymeric IgA binds C1q, but does not activate C1. 221 79

Cleavage of mouse IgA T15 with papain yielded (a) a glycosylated Fab fragment, (b) a non-glycosylated Fc fragment and (c) a glycosylated C-terminal peptide. The cleavage sites at the hinge and at the end of the C alpha 3 domain were located by sequencing. The two glycopeptides were prepared from the Fab and C-terminal fragments by pronase digestion. The C alpha 1 glycopeptide at Asn 155 was complex type with alpha (1-3)galactose terminal groups, and closely resembled the Asn 171 glycopeptide of mouse IgM (Anderson et al. (1985) Arch. Biochem. Biophys. 243, 605-618). In contrast, the C-terminal glycopeptide at Asn 446 was entirely different from the corresponding IgM glycopeptide, being complex rather than high-mannose type.
Mol Immunol 1990 Nov
PMID:The glycopeptides of the mouse immunoglobulin A T15. 224 87

The antigen-limiting nature of microtiter ELISAs predicts that antibodies of minor classes may be underestimated when the same specimen contains large amounts of IgG antibodies specific for the same antigen. Such competitive inhibition can be diagnosed from ELISA titration plots. A method is described to eliminate the negative effects of this competition on the detection of IgA antibodies in rabbit serum. The detectability of rabbit serum antibodies to ovalbumin and bovine serum albumin is increased 10-fold by prior treatment of 1:100 dilutions of serum with 1% Cowan I S. aureus. High concns of S. aureus, e.g. 10%, completely deplete serum IgG without loss of IgA. However, concns higher than 1% do not lead to additional improvement in the detectability of IgA antibodies in the systems studied. The method is rapid, inexpensive and shows no non-specific depletion of IgA from either serum or bronchoalveolar lavage fluid.
Mol Immunol 1990 Apr
PMID:The antigen-limited nature of microtiter ELISAs requires partial depletion of IgG to permit reliable determination of rabbit serum IgA antibody activity. 235 10

Radioimmunoassays for C3a and C4a have been used to measure the activation of complement during the formation of immune complexes in human serum by the interaction of DNP-BSA and each of 11 mouse anti-DNP monoclonal antibodies of varied isotype and affinity. Those containing IgG2 or IgM were potent activators of C4, whilst IgG1 containing complexes were less efficient. C3 activation in normal serum was similar for complexes containing IgG1, IgG2a, IgG2b or IgM. IgA complexes did not activate C3 or C4. All complexes except those containing IgA precipitated more slowly in serum than in buffer. IgG2 antibodies were potent activators despite being very slow to precipitate in buffer. In serum containing EGTA activation of C4 was abolished and precipitation of complexes occurred at the same rate as in buffer. Nevertheless, C3 activation still occurred by the alternative pathway for all IgG and IgM complexes. Antibodies of the same isotype did not necessarily activate complement to the same extent. The ranking of the ability to activate complement was the same as that observed when performed complexes containing the same antibodies were added to serum. The levels of C4a generated were similar under both conditions but for most antibodies more C3a was generated by preformed complexes.
Mol Immunol 1990 May
PMID:The effect of antibody isotype on the activation of C3 and C4 by immune complexes formed in the presence of serum: correlation with the prevention of immune precipitation. 236 59

An enzyme-linked immunosorbent assay (ELISA) was developed for the quantitative measurement of IgG antibodies to the immunodominant R-D-Ala-D-Ala-OH determinant of peptidoglycan. Synthetic peptides R-D-Ala-D-Ala-OH, revealing structural analogy with the C-terminal sequence of the antigenic determinant H-L-Ala-D-Glu(L-Lys-D-Ala-D-Ala-OH)-NH2 of peptidoglycan, were coupled covalently to albumin via their amino groups. The resulting peptidyl proteins were employed as an antigen in an ELISA for the specific detection of human IgG antibodies against the C-terminal R-D-Ala-D-Ala-OH moiety of H-L-Ala-D-Glu(L-Lys-D-Ala-D-Ala-OH)-NH2. Antigenic specificity was proved by comparing the high binding to albumin-(D-Ala-D-Ala-D-Ala-OH)9 with a lack of binding to albumin-(L-Ala-L-Ala-L-Ala-OH)13 and by appropriate inhibition studies of the ELISA. IgG, totally free from IgA and IgM, was isolated from reference serum 004, and the particular specificity was entirely found in this fraction. Quantification of the ELISA was effected by affinity chromatography. Isolated IgG was applied to an affinity column of Sepharose-[albumin-(D-Ala-D-Ala-D-Ala-OH)9]n, unbound IgG was eluted with phosphate-buffered saline and specific IgG against the C-terminal R-D-Ala-D-Ala-OH moiety of H-L-Ala-D-Glu(L-Lys-D-Ala-D-Ala-OH)-NH2 was eluted with 6 M guanidinium chloride.
Mol Immunol 1985 May
PMID:Quantitative determination of human IgG antibodies to the peptide subunit determinant of peptidoglycan by an enzyme-linked immunosorbent assay. 241 Jul 75

alpha 1-Microglobulin (alpha lm), a glycoprotein heterogeneous in charge, was reported to occur both as a 31-kilodalton (kd) monomer [low mol. wt alpha lm (LMW-alpha lm)] and as polymers or complexes formed with other plasma proteins including IgA [high mol. wt alpha lm (HMW-alpha lm)]. The present study was designed to characterize HMW-alpha lm in normal human serum and in myeloma sera. The following sera were selected: five IgG, 16 IgA and four Bence-Jones protein myelomas. alpha lm was identified by specific monoclonal antibodies in competitive radioimmunoassay and solid-phase ELISA. HMW-alpha lm was found to be associated almost exclusively with monomeric IgA and possibly in very small proportion with dimeric IgA. Ever in cases of predominantly dimeric IgA myelomas, alpha lm was associated with the monomeric form of the monoclonal IgA. The molar ratio of HMW-alpha lm to monomeric IgA never exceeded 3.5% and it was estimated to range from 0.5 to 1.4% in normal serum. No association with other proteins than IgA and no alpha lm polymers were found in IgA myeloma. Two types of HMW-alpha lm-IgA complexes were found: (a) those that were dissociable into IgA and LMW-alpha lm after mild reduction, and (b) those which were dissociated only after complete reduction of the complexes into IgA and an 88-90-kd component bearing alpha lm but no IgA epitopes. It was concluded that either of the two molecular species of alpha lm bearing common epitopes, with apparent mol. wts of 31,000 and 88,000-90,000, respectively, could form stable complexes with monomeric IgA. The association is likely to be performed through disulfide bridges. Nearly all the 88-90-kd but only a small proportion of the 31-kd component is associated with IgA.
Mol Immunol 1985 Jun
PMID:Complexes of alpha 1-microglobulin and monomeric IgA in multiple myeloma and normal human sera. 241 Jul 80

Radioiodinated human secretory IgA (sIgA) injected intravenously into mice was rapidly cleared from the circulation by the liver. A portion of the sIgA was transported as an intact molecule into the bile. However, this transport was less efficient than that of human serum polymeric IgA (pIgA). The clearance of sIgA from the circulation was inhibited by prior injection of asialofetuin, suggesting that its uptake is mediated by the hepatic binding protein (HBP) specific for asialoglycoproteins. Mouse pIgA did not inhibit the hepatic clearance of sIgA. Results of in vivo studies were confirmed by in vitro experiments. The binding of 125I-asialoorosomucoid to either the particulate fraction (2000 g pellet of the homogenate) or the plasma membrane fraction of mouse liver was inhibited by sIgA. When polypeptide components of sIgA were used as inhibitors, significant inhibition was obtained with secretory component (SC), while inhibition with light and J-chains was not statistically significant. Examination of the inhibitory activity of IgA1 and IgA2 myeloma proteins and heavy chains isolated from these proteins revealed that binding of polymeric IgA1 and alpha 1 heavy chains can also be mediated by HBP. However, these interactions appear to be of lower avidity than those with SC. The inhibitory activity of human IgA2 and alpha 2 heavy chains was not significant. The involvement of HBP in binding of sIgA was also confirmed by measuring the inhibition of binding of 125I-sIgA. The binding of this protein by the particulate fraction of the mouse liver homogenate was inhibited by asialoglycoproteins and SC while inhibition with IgA1 and alpha 1 heavy chains was not significant. These results suggest that the carbohydrate moieties recognized by HBP reside primarily in the SC portion of sIgA.
Mol Immunol 1985 Aug
PMID:Carbohydrate-mediated clearance of secretory IgA from the circulation. 241 48

Twelve C57BL/6J hybridoma clones, 9, 2 and 1 from mice immunized with stearyl-isomaltotetraose, stearyl-isomaltopentaose and stearyl-isomaltohexaose respectively were characterized. Seven produced IgA and 5 IgM. The specificities and sizes of their combining sites were determined by quantitative precipitin and precipitin inhibition assays. All 12 hybridoma antibodies precipitated with alpha 1----6 dextran B512 and linear dextran LD7, indicating that they recognize an internal -Glc alpha 1----6Glc alpha 1----6Glc- determinant. This in contrast with the results with rabbit antisera obtained in response to the same immunogen which recognize the non-reducing terminal determinant Glc alpha 1----6Glc alpha 1----6Glc-. Of the 12 hybridoma antibodies, 1 has an antibody combining site complementary to 4 alpha 1----6-linked glucoses while others have combining sites complementary to isomaltohexaose or isomaltoheptaose. The large combining-site sizes found in C57BL/6 hybridoma clones may be related to the pre-existing clonal repertoire in this strain. Binding constants of monomers of these antibodies for dextran B512 and isomaltoheptaose determined by affinity electrophoresis range from 1.4 X 10(3) to 4.6 X 10(5) ml/g and from 1.2 X 10(3) to 3.5 X 10(4) M-1 respectively, which is consistent with previous studies in the anti-dextran B512 system. The use of synthetic glycolipids as antigens enables us to study the gene control of antibody responses to glycolipids and to investigate the combining-site specificities of antibodies to a single antigenic determinant. Results so far show that all 12 hybridoma proteins are different despite the simplicity of the antigens. The findings provide further insight into the specificity of antibody combining sites.
Mol Immunol 1985 Sep
PMID:Immunochemical studies of conjugates of isomaltosyl oligosaccharides to lipid: production and characterization of mouse hybridoma antibodies specific for stearyl-isomaltosyl oligosaccharides. 241 10

Rabbits and swine immunized with TEPC 15 IgA, goats immunized with T15-positive IgM and swine immunized with affinity-pure swine anti-phosphorylcholine (PC) all produce antibodies which recognize a hapten-inhibitable idiotypic determinant on swine anti-PC. The similarity in reactivity and order of inhibitability with various PC analogs of the heterologous (swine anti-TEPC 15) and isologous (swine anti-swine anti-PC) reagents indicates that they recognize a related idiotype and suggest it may be the predominant idiotype expressed on swine anti-PC antibodies. The heterologous and isologous anti-idiotypic reagents generated in this study recognize swine and mouse anti-PC but not normal swine IgM, IgG or MOPC 460. Only reactions with swine anti-PC and mouse T15-positive anti-PC proteins are hapten-inhibitable. The greater inhibitory capacity of trimethylammonium and acetylcholine than PC suggests that the idiotope(s) recognized on swine anti-PC by the anti-idiotypic reagents is integral rather than peripheral to the anti-PC binding site. The nearly exclusive IgM anti-PC response of swine to Streptococcus pneumoniae R36A and PC-Brucella have so far hindered attempts to study the isotypic distribution of the idiotype.
Mol Immunol 1985 Oct
PMID:Identification and characterization of a hapten-modifiable TEPC 15 cross-reactive idiotype in swine. 241 8

Isotype distribution was analyzed, as a function of age in MRL/Mp-lpr and MRL/Mp-+ mice. The mice were tested for: (1) "spontaneous" response to nucleic acid (2) induced response to alum-precipitated phosphorylcholine-rabbit gamma globulin (PC-RGG) (immunized animals) and (3) induced response to alum-precipitated PC-RGG after pretreatment with aggregate-free RGG (tolerized-immunized animals). "spontaneous" nucleic acid antibodies of isotypes, other than IgM, increased as animals became older. The quantity of RGG antibody declined as a function of the age at which animals were immunized. Young tolerized-immunized animals made less antibody of all isotypes than did immunized animals. In later life, resistance against tolerance induction developed. Aggregate-free RGG sensitized older animals and, thus, augmented the response to alum-precipitated PC-RGG. Up to the age of 20 weeks, spontaneous antibody and antibody of tolerized-immunized animals showed striking similarities in age- and strain-dependent changes of IgG2b and IgA isotypes. Results were discussed in terms of: (1) a defect in down regulation of immune responsiveness, which contributes to the initiation of autoimmunity and age-dependent resistance to tolerance induction; (2) regulatory mechanisms for isotype switching, which contribute to resistance to tolerance induction, whether naturally occurring or experimentally induced; and (3) age-related immunological changes which are inherent in the MRL/Mp genome, the mutant gene, lpr/lpr, accelerating the changes.
Mol Immunol 1985 Dec
PMID:Immune response, tolerance circumvention and autoantibodies in aging MRL/Mp-lpr and MRL/Mp-+ mice. 242 Nov 55


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