Immunochemical studies on mouse myeloma proteins reactive with dextrans or with fructosans and on human antilevans

V and C gene contribution in creating anti-alpha-1,3 dextran antibodies in mice. II. Characteristics of Ig-lb to e prototype responses

The light (L) and heavy (H) chain and the idiotypic (Id) composition of the antibody (Ab) plaque-forming cells (PFC) and serum Ab specific for alpha-1,3 dextran have been characterized in murine strains exhibiting the CH-Ig-lb to e allotypes and in their F1 hybrids with Ig-la1, BALB/c prototypes. The Ab response of the Ig-lb to e mice to the alpha-1,3 dextran was low in the kappa (kappa) L chain class with only a minor, sporadic Ab in the lambda (lambda) L chain class discernible after prolonged immunization. Two of a total of sixty-eight C57Bl/6 Ig-lb mice, in a total of 318 Ig-lb to e mice tested, exhibited, in late responses, a significantly elevated Ab in the lambda L class at both serum and PFC levels, equalling at the PFC level the total non-specific lambda PFC values. An Id analysis showed this lambda Ab and the kappa Ab to lack the Id relatedness to the three BALB/c alpha-1,3 dextran-binding myeloma proteins (MP) Ab prototypes, J-558, 104 E, and UPC-102, exhibited by the lambda Id+ Ab of the Ig-la1 BALB/c prototypes and their F1 hybrids with the Ig-lb to e prototypes. Furthermore, affinity differences could be detected by alpha-1,3 nigerodextrans, PFC inhibition analysis, between the late C57Bl/6 anti-alpha-1,3 dextran lambda Id--Ab PFC and the lambda Id+ Ab PFC of the BALB/c and their F1 progeny.

V and C gene contribution in creating anti-alpha-1,3 dextran antibodies in mice. I. Characteristics of Ig-lal prototype responses

The light (L) and heavy (H) chain and the antigenic, idiotypic (Id) composition of the antibody (Ab) plaque-forming cells (PFC) and serum Ab specific for alpha-1,3 dextran have been characterized in Ig-lal BALB/c prototype mice, in Ig-la- [30] mice, and in BALB/c congenic and recombinant strains. Four distinct Ab Id specificities were identified by using criteria of Id relatedness to three Id-distinct, alpha-1,3 dextran-binding BALB/c myeloma proteins (MP), all associated, in the Ig-lal mice with the lambda (lambda) chains: a major, common IdX in 40--90% of the molecules; three minor, individual IdI in 1--49% of the molecules; and a fifth, Id-undefined one. These specificities were expressed at the PFC and serum level in the mu and gamma isotypes. A minor, kappa (kappa), Id-negative Ab was discerned only at the PFC level. The Ig-la- CBA and C3H mice responded with anti-alpha-1,3 dextran, kappa Id-negative Ab. The BALB/c, congenic strain CB20 (BALB/c Ig-lb, carrying the C57Bl/Ka, Ig-lb variable H (VH) gene complement and CH phenotype, made anti-alpha-1,3 dextran kappaId-negative Ab of the Ig-lb prototype. The recombinant BAB/14, carrying in the C57Bl/Ka CH-Ig-lb phenotype the BALB/c Ig-lal VH gene(s) controlling anti-alpha-1,3 dextran lambda Ab responsiveness and Id specificity (VH-DEX+), express the BALB/c lambdaId repertoire.

Preparation of functionalized derivatives of inulin: conjugation of erythrocytes for hemagglutination and plaque-forming cell assays

A method is described for preparing derivatives of alkali-stable polysaccharides for coupling to immunogen carriers or to sheep red blood cells (SRBC) for use in hemagglutination (HA) and plaque-forming cell (PFC) assays. Inulin, a beta (2 leads to 1)-linked polyfructosan was partially derivatized with carboxyl, aminoethyl or (p-aminophenyl)butyryl groups; the latter derivative was coupled to SRBC following diazotization. Optimal conditions for the sensitization of SRBC with inulin were given. The immunological reactivity of the inulin molecule was unaffected by the derivatization reactions, and high, reproducible anti-inulin HA titers for inulin-binding myeloma proteins were found using these specifically sensitized SRBC. The sensitized SRBC were stable for assays for over 2 weeks. Problems with spontaneous agglutination or distortion of sensitized SRBC, normally seen in other procedures, e.g., methods using stearoyl-inulin, were not encountered.

The cell wall-associated levansucrase of Actinomyces viscosus

Actinomyces viscosus produces both a soluble extracellular levansucrase and a cell wall-associated levansucrase. The enzyme from cell walls was solubilized by lysozyme digestion. The soluble extracellular and cell wall-associated forms of the enzyme were compared and appeared to be identical, based on molecular weight estimations, kinetic parameters, and reactions with antisera. The product of both forms of the enzyme was a high molecular weight, branched levan, as shown by its reactivity with myeloma proteins specific for beta(2 leads to 1) and for beta(2 leads to 6) linkages in fructosans. Although levansucrase remained tightly bound to the levan which it synthesized, the enzyme did not bind to exogeneously added levan. Regarding the potential pathogenicity of the levan product, pure levan, produced using purified levansucrase, did weakly activate complement by the alternative pathway. However, the pure levan did not directly cause bone resorption in an in vitro bone resorption assay.

Immunochemical studies on dextran-specific and levan-specific myeloma proteins from NZB mice

Two dextran-specific (PC 3858 and PC 3936) and one levan-specific (PC 3660) NZB myeloma proteins were studied by quantitative precipitin and precipitin-inhibition assays. Both myeloma antidextrans were alphaD-(1 leads to 6) specific and precipitated strongly with a synthetic, linear dextran, molecular weight 35,500, and with other dextrans. The two myeloma antidextrans differed with respect to their relative reactivities with dextrans containing various proportions of alpha-D-(1 leads to 6), alpha-D-(1 leads to 4)-like, and alpha-D-(1 leads to 3)-like linkages. In inhibition assays, the two antidextran myeloma proteins behaved differently from each other, from alpha-D-(1 leads to 6)-specific BALB/c myeloma antidextrans, and from the human antidextrans previously studied. Isomalto-oligosaccharides IM3, IM4, and IM5 were all equal in inhibitory power but were only about 60% as potent as IM6 and IM7, which also inhibited equally on a molar basis. Although precipitation with linear dextran suggests that both may have groove-type sites, as previously inferred for QUPC 52, the size of their combining sites is uncertain. It is not clear whether the sites are only as big as three glucose residues with the increased inhibition by six and seven glucose residues being attributable to partial bivalence and to their ability to combine in several ways along the chain, or whether the site is as big as six glucose residues with the increment in binding by the fourth and fifth glucose residues being minimal and the sixth contributing considerable additional binding-energy. The fructan-specific myeloma protein did not react with inulin, but reacted with many levans and with perennial rye-grass levan containing only beta-D-(2 leads to 6) links. The levan-antilevan reaction was not inhibited by beta-D-(2 leads to 1)- linked oligosaccharides. The findings suggest that PC 3660 has a specificity for (2 leads to 6)-linked chains.

Cell-associated levan of Actinomyces viscosus

Actinomyces viscosus ATCC 15987 was examined for the presence of cell-associated levan by absorption of myeloma proteins with antilevan activity and direct immunofluorescence. Levan was not detectable on the surface of glucose-grown A. viscosus, but after a brief incubation of these cells with 5% sucrose, they were encapsulated with tenaciously adhering levan. The levan layer constituted between 0.02 and 0.03% of the cell dry weight. In contrast, sucrose-grown A. viscosus cells possessed a low level of cell-associated levan, which was only moderately increased by incubation in sucrose and which partially existed as a loose slime rather than a tenacious capsule.

Levan and levansucrase of Actinomyces viscosus

A levansucrase was demonstrated in the growth medium and in association with the cell surface of Actinomyces viscosus. The amount of enzyme produced relative to cell density is not significantly affected by the growth conditions. Sugar alcohols inhibit growth of the cells. The levansucrase hydrolyzes sucrose to produce free glucose and levan; some free fructose is also formed. There is no requirement for cofactors. The Km for sucrose is 12 mM. A variety of heavy metal ions and two disaccharides, lactose and cellobiose, inhibit the enzyme. The levansucrase was purified to homogeneity and has a specific activity of 90 micronmol of glucose release per min per mg. The enzyme has a molecular weight of 220,000 and is composed of subunits of molecular weight 80,000. The levan product contains both beta(2 leads to 1) and beta(2 leads to 6) linkages. The enzyme remains tightly bound to the levan product, resulting in the formation of high-molecular-weight polymer on the order of 10(8) daltons. The possible role of the levan and levansucrase of A. viscosus in the pathogenesis of periodontal disease is discussed.

Binding properties of immunoglobulin combining sites specific for terminal or nonterminal antigenic determinants in dextran

Binding constants of the dextran-reactive BALB/c mouse IgA myeloma proteins W3129 and QUPC 52 have been determined for each member of the isomaltose series of oligosaccharides and for methyl alphaDglucoside. Protein W3129 has maximum complementarity for isomaltopentaose (IM5) deltaf degrees = 7,180 cal/mol) with 55-60% of the total binding energy directed against methylalphaDglucoside. Protein QUPC 52 gives maximum binding with isomaltohexaose (IM6) (deltaF degrees = -5,340 cal/mol) and has about 70% of its total binding energy for isomaltotriose (IM3), but at most only 5% for isomaltose (IM2) or methyl alphaDglucoside. Protein W3129 precipitates with branched dextrans high in alpha (1 yields 6) linkages and reacts with but does not precipitate a synthetic alpha (1 yields 6)-linked linear dextran. Protein QUPC 52 precipitates both branched and linear dextrans. Thus, the immunodominant group for protein W3129 is mimicked by methyl alphaDglucoside and this protein reacts exclusively at the terminal nonreducing ends of alpha (1 yields 6)-linked dextran chains. Protein QUPC 52 has an immunodominant group which is expressed by IM3 but not smaller oligosaccharides and this protein can react at nonterminal locations along alpha (1 yields 6)-linked dextran chains. Precipitation of linear dextran seems to be a valid although not quantitative assay for antidextrans with nonterminal specificity. Quantitative precipitin reactions with branched and linear dextrans suggest that alpha (1 yields 6)-specific human antidextrans are mixtures of molecules having terminal and nonterminal specificities and that the fraction of each type can vary among individuals. Rabbit antisera against IM3 or IM6 coupled to bovine serum albumin also appear to contain antibodies with nonterminal specificity for dextran chains although a large fraction has terminal specificity. Low molecular weight clinical dextran N-150N (congruent to 60,000) reacted more like linear dextran than like its parent native-branched dextran B512. This is thought to result from an abundance of nonterminal determinants in clinical dextran N-150N but a very small number of functional terminal determinants per molecule. An appreciation of terminal and nonterminal specificities and of the different immunodominant structures in isomaltosyl chains has proven to be of a great value in understanding the immunochemical reactions of dextrans. Moreover, certain previous findings with fructosan-reactive mouse myeloma proteins and human antilevans (55, 84) also suggest terminal and nonterminal specificities for levan chains.

Multiple individual and cross-specific indiotypes on 13 levan-binding myeloma proteins of BALB/c mice

13 leven-binding myeloma proteins (LBMP) of BALB/c origin were classified into two groups with different binding specificities; one group of 11 proteins bound beta2 leads to 1 fructosans, a second group of two proteins bound fructosans probably of beta2 leads to 6 linkage. Anti-idiotypic sera prepared to 10 of the proteins in the appropriate strains of mice identified numerous idiotypic determinants. Each protein used for immunization had its own unique individual idiotypic specificities (IdI) and in addition most of the proteins carried two-nine cross-specific or shared idiotypes (IdX) that were found only among LBMP, and not found in 106 non-LBMP. Most of the IdX determinants and only four of the IdI determinants of the beta2 leads to 1 fructosan binding group were located in the antigen-binding site. The multiplicity of antigenic differences in this functionally related group of immunoglobulins reveals an unexpected degree of heterogeneity in V-regions that appears to be unrelated to binding.

A common idiotype on human macroglobulins with anti-I and anti-i specificity

The reactions of an idiotypic antiserum prepared against an anti-I cold agglutinin (Da) were studied in radioimmunoassays which were designed to detect partial rather than complete idiotypic cross-reactions among cold agglutinins with anti-I and anti-i activity. Proteins showing strong idiotypic cross-reactions by gel precipitation could not inhibit the binding of 125I-labelled Da to anti-Da (individual specificity). It was necessary to use 125I-labelled cross-reactive proteins in order to demonstrate cross-idiotypic specificity and even the choice of the reference cross-reactive protein was important. The use of the 125I-labelled Fab fragment of a cross-reactive anti-I cold agglutinin (Low) allowed the detection of an idiotypic determinant common to at least 73% of cold agglutinins with specificity for the I-i antigen complex. Among these were two transiently occurring cold agglutinins following M. pneumoniae infection and infectious mononucleosis. This idiotypic determinant was not detected on cold agglutinins with anti-Pr specificity or on isolated monoclonal IgM or IgG lacking cold agglutinin activity, but it was present in low concentrations in pooled IgG. The common idiotypic determinant was found on IgM kappa cold agglutinins belonging to different VK subgroups and on an IgM lambda protein. A knowledge of the structural basis of such idiotypic cross-reactions among proteins from unrelated individuals should provide important information about the genes controlling the synthesis of site-related regions of antibodies.

Structural, functional, and idiotypic characteristics of a phosphorylcholine-binding IgA myeloma protein of C57BL/ka allotype

An IgA phosphorylcholine (PC)-binding myeloma protein with IgCH allotypic determinants different from those of BALB/c mice is characterized. The myeloma, CBPC 2, was induced in the CB-20 strain of mice which is congenic to BALB/c but differs from it by carrying the A15 allotypic determinant of C57BL/ka mice. Sequence analysis of the CBPC 2 light chain through the first hypervariable region, as well as isoelectric point analysis, show that this chain is indistinguishable from that of T15, a PC-binding myeloma protein of BALB/c origin. The heavy chains of CBPC 2 and T15 differ by only two amino acids (positions 14 and 16) through the first hypervariable region. As measured by inhibition of precipitation, both CBPC 2 and T15 have the same specificity for PC, glycerophosphorylcholine, acetylcholine, and choline. In addition, CBPC 2 possesses the binding site-associated idiotypic determinant which is present on T15. However, like normal or induced C57BL/6 anti-PC antibody, it does not possess the nonbinding site idiotypic determinant.

A new, mouse-myeloma immunoglobulin A having specificity for beta-D-(1 yields 6)-linked D-galactopyranosyl residues

The discovery of T601, a new mouse-myeloma immunoglobulin A having specificity for beta-D-(1 yields 6)-linked D-galactopyranosyl residues, brings the total number of known antigalactan immunoglobulins to seven. The interaction of T601 with a number of ligands has been investigated. For those ligands showing interaction with the immunoglobulin, the affinity constants have been quantitatively measured by tryptophanyl fluorescence. The values show that protein T601 behaves very similarly to protein X24.

Clonal nature of the immune response to phosphorylcholine. IV. Idiotypic uniformity of binding site-associated antigenic determinants among mouse antiphosphorylcholine antibodies

A new idiotypic determinant(s) on mouse anti-PC antibodies is described. Antibodies to the determinant(s) were raised in rabbits by immunization with HOPC 8, a PC-binding myeloma protein, and were isolated from HOPC 8 immunoadsorbent by elution with PC. These antibodies react with binding site determinants on anti-PC antibodies raised in all 15 inbred mouse strains tested regardless of histocompatibility or allotype, but fail to react with antibodies of other specificities or with anti-PC antibodies raised in other rodent species. These results correlate closely with other studies which show similar binding specificity of anti-PC antibodies raised in 17 different strains of mice. The site-associated idiotypic determinant(s) is clearly distinct from that detected by mouse anti-HOPC 8 antisera. This latter determinant(s) is present on anti-PC antibodies of only a few strains of mice and may not be in the binding site.

Immunochemical analysis of the idiotypes of mouse myeloma proteins with specificity for levan or dextran

This paper deals solely with idiotypic determinants, the configurations of which are modified when the antibody bearing them interacts with its ligand. This phenomenon is measured as an inhibition of the reaction between anti-idiotype and idiotype. Two points are made: (a) The assay for ligand-modifiable determinants can be used to determine the "size" of the combining site. This is illustrated here with the anti-alpha(1 --> 6) dextran mouse myeloma immunoglobulin W3129. Whether the interaction between a homologous series of alpha(1 --> 6) oligosaccharide ligands and the combining site of W3129 is measured by inhibition of precipitation with alpha(1 --> 6) dextran (4) or of binding of W3129 to anti-W3129 idiotype, the finding is the same. The order of inhibition is isomaltohexaose = isomaltopentaose >> isomaltotetraose > isomaltotriose >>> isomaltose. The combining site is optimally complementary to isomaltopentaose. (b) Cross-idiotypic specificity is closely correlated with cross-combining specificity; the converse is not true. This is illustrated here with three groups of mouse myeloma immunoglobulin, each specific for alpha(1 --> 3) dextran, alpha(1 -->6) dextran, beta(2 --> 1) or beta(2 --> 6) levan. If a given anti-idiotypic serum cross-reacted with several myeloma proteins, they always had similar combining specificity. Thus the three proteins, J558, MOPC 104E, and UPC 102, which cross-react with anti-J558 have combining specificity for alpha(1 --> 3) dextran; cross-reacting W3082, UPC 61, and Y5476 have specificity for levan; and cross-reacting W3129 and W3434 have specificity for alpha(1 --> 6) dextran. This extends previous studies with proteins specific for phosphorylcholine (7) or gamma-globulin (8). As expected, the converse is not true, for proteins may have combining specificity for alpha(1 --> 6) dextran e.g. QUPC 52, or levan e.g. J606, UPC 10 and yet not carry the above-mentioned reference idiotypes. The correlation between cross-idiotypic and combining specificity breaks down when idiotypic determinants which are not modifiable by ligand are studied. The implications of this are pointed out since most investigations deal with ligand-nonmodifiable determinants.