The interaction of mouse myeloma immunoglobulin S15 with negatively charged polysaccharide antigens

Observations on the binding of four anti-carbohydrate monoclonal antibodies to their homologous ligands

The binding of four monoclonal immunoglobulins, two with specificity for beta(1-->6)-linked D-galactopyranans (IgA X24 and IgA J539) and two with specificity for the chain terminus of alpha(1-->6)-linked d-glucopyranans (IgA W3129 and IgA 16.4.12E), was measured with a number of their homologous oligosaccharide ligands at different temperatures. The results show a linear relationship between lnKa and 1/T, where Ka is the affinity constant and T is the absolute temperature. The unitary free energy of binding, DeltaGu, is virtually independent of T, and the DeltaSu is small when compared with DeltaGu. The enthalpy changes derived from van't Hoff plots are large and negative, indicating an exothermic binding effect, whereas the entropy changes are small and negative, indicating minor overall hydrophobic contributions. Measurements of the free energies of binding, in low and high salt buffers, of methyl beta-d-galactopyranoside and the methyl glycoside of beta(1-->6)-D-galactopyranotetraose with anti-galactan IgA X24 indicate that the monosaccharide has no hydrophobic interaction with the highest affinity subsite of IgA, whereas the tetraoside might have a modest hydrophobic interaction with the three other hapten-binding subsites of IgA. The standard entropy change of binding of the two groups (galactosyl and glucosyl) of oligosaccharides to the two respective sets (anti-galactan and anti-dextran) of antibodies shows a distinct, differing correlation with the hapten chain length within each set. This correlation agrees with the type of association previously established between the antibodies and either the interior determinants of the antigen (in the case of the anti-galactans) or the chain terminus (in the case of the anti-dextrans).

Antigen-binding diversity of human hybridoma autoantibodies derived from splenocytes of patients with SLE

The antigen-binding specificity of human hybridoma-derived monoclonal autoantibodies (mAb) was analysed with mAbs derived from the spleens of two patients with active systemic lupus erythematosus (SLE). From one patient 72 mAbs (RSP clones) and from the other 173 mAbs (RT clones) were obtained. The binding specificity of these mAbs was analysed by solid- and fluid-phase ELISA against the autoantigens ssDNA, dsDNA, cardiolipin, SmRNP, histones, Sm-D and SS-B (La) synthetic peptides, and foreign antigens including bacterial polysaccharides. In addition, antinuclear antibody activity and anti-dsDNA binding were confirmed by fluorescence staining methods. Reflecting the patient's serological profile, none of the antibodies from the RSP clones reacted with ssDNA or dsDNA but 12 reacted with cardiolipin. In addition, three mAbs reacted with H4, five with U1 RNP, two with Sm-D peptides and 12 with SS-B peptides. In contrast, from the RT fusion, nine mAbs reacted with ssDNA, HI and SS-B peptides, seven with cardiolipin, four with dsDNA, two with Sm-D peptides and one each with H2A, H3 and H4. In many cases one mAb showed reactivity with more than one antigen: for example, mAb RT 72 binds to ssDNA, dsDNA, cardiolipin, H1, H4 and an Sm-D peptide; RT 6 binds to H1, SmRNP and ubiquitinated histone H2A. However, none of the antibodies showed 'across the board' polyreactivity; indeed, the selectivity of the reactions was notable and marked variation in antibody affinity was recorded. Eight of the mAbs bound to Salmonella typhimurium and two to the Klebsiella polysaccharide K-30.(ABSTRACT TRUNCATED AT 250 WORDS)

Two M315 idiotopes defined by isologous monoclonal antibodies: one depends on germline and the other on mutated murine lambda 2 light chain sequences

We have previously reported that T helper cells of BALB/c mice recognize the unique mutated sequence Phe94, Arg95, Asn96 of the lambda 2 L chain of isologous (BALB/c) myeloma protein 315. Here we study two Id (Id-315.1.4 and Id-315.TH) of the DNP-Lys binding M315 defined by two monoclonal isologous anti-Id Ab (Ab 2-1.4 and Ab 2-TH). Both Id were (1) totally expressed by Fv-315, but not by free unpaired V domains, (2) specifically dependent on VH-315, since lambda 2-315 recombined with four other H chains did not express the Id, (3) related to the hapten-binding site because their expression was blocked by the haptens DNP-Lys and DNP-Gly, and (4) topographically related because Ab 2-1.4 and Ab 2-TH competed with each other for binding to M315. The contribution of lambda chain V regions was studied with the aid of reconstituted Ig molecules of H-315 paired with lambda 1, lambda 2, and lambda 3 L chains. Id-315.TH was expressed equally well by reconstituted Ig containing three different lambda 2 chains (lambda 2-5-7, lambda 2-T952, and lambda 2-315), but its expression was profoundly reduced when H-315 was associated with lambda 3-SAPC15 or lambda 1-J558 L chains; it therefore depended upon amino acids encoded by germline lambda 2 genes. By contrast, Id-315.1.4 was only restored by the lambda 2-315 chain paired with H-315. Since lambda 2-5-7 and lambda 2-T952 differ from lambda 2-315 at positions 38, 94, 95, 96, and 98 or 99, respectively, Id-315.1.4 probably requires the unique mutated amino acids Phe94, Arg95, Asn96 of lambda 2-315. This resembles the effects on Id expression of previously reported unique amino acids of the D region. We failed to confirm that hyperimmunization of BALB/c mice with Ab 2-1.4 cross-linked to KLH induced M315-like Ab. The results are discussed in terms of the contribution of the third hypervariable loop of lambda chains to Id and the immunogenicity of isologous Ig.

Repertoire of murine lambda-positive variable domains: polyclonal induction of lambda isotypes and their associated pattern of antibody specificities

The diversity of lambda variable (V lambda) domains is extremely restricted when compared to those of VH and V kappa. In addition, each V lambda domain is determined by the C lambda domain. For these reasons, the lambda system is an excellent model for the study of the associated VH region repertoire. The study of V lambda domain diversity has been limited by the small contribution (approximately 5%) of lambda-bearing proteins to the total Ig pool. We now show that treatment of BALB/c mice with rabbit anti-lambda 1 antibodies coupled to lipopolysaccharide induces a production of polyclonal lambda 1 light chain-bearing Ig whereas, conversely, treatment with rabbit anti-lambda 2 antibodies induces a production of polyclonal lambda 2 + lambda 3 light chain-bearing Ig. The antigenic specificities of these two distinct lambda populations were then studied using B1355 dextran, (4-hydroxy-3-nitrophenyl)acetyl (NP) and 2,4-dinitrophenyl (DNP) as antigens. The anti-alpha(1-3)dextran antibody specificity was found to be mediated exclusively by antibodies bearing the lambda 1 isotype whereas the anti-NP and anti-DNP antibody specificities are mediated by both the lambda 1 and lambda 2 + lambda 3 isotypes. In addition, various mouse strains with the VHa or VHb allotypic haplotype and the rlo lambda 1 or r+ lambda 1 phenotype were treated with rabbit anti-lambda 1 antibodies. The lambda 1 anti-NP and anti-DNP antibody specificities were similar in all strains whereas the lambda 1 anti-alpha(1-3)dextran specificity was linked to the presence of the VHa allotypic haplotype. The mouse strains with the rlo lambda 1 or r+ lambda 1 phenotype did not differ in terms of their patterns of lambda 1 antibody specificities.

A single germline VH gene segment of normal A/J mice encodes autoantibodies characteristic of systemic lupus erythematosus

These experiments tested the hypothesis that unmutated germline genes from normal mice can encode autoantibodies. We found that the unmutated VHIdCR gene segment, which encodes a large proportion of antiarsonate antibodies in A/J mice, also encodes antibodies with the ability to bind to DNA and cytoskeletal proteins. After Ars immunization, at a time when the VHIdCR gene segment mutates and antibody affinity for the hapten increases, reactivity with the autoantigens was lost. Six antibodies obtained after immunization with Ars bound both the Ars and DNA. Results of competitive inhibition assays suggested that the same variable region site in the antibodies bound to both Ars and DNA. The properties of the individual germline-encoded antibodies, which include reactivity to both DNA and cytoskeletal proteins, suggest that autoantibodies characteristic of SLE might be a subset of antibodies encoded by unmutated germline V genes.

The regulatory locus r lambda 1 affects the level of lambda 1 light chain synthesis in lipopolysaccharide-activated lymphocytes but not the frequency of lambda 1-positive B cell precursors

Several strains of mice, most notably the SJL strain, have a greatly reduced level of circulating lambda 1 immunoglobulins (r lambda 1 lo phenotype) compared with other mice. The locus responsible for this phenotype has been shown to be closely linked to the structural C lambda 1 gene. Functionally this locus has been said to reduce the number of lymphocytes expressing surface lambda 1 molecules. In order to gain a better understanding of this phenomenon we compared the functional properties of activated B cells secreting lambda 1 immunoglobulins in the splenocytes of both BALB/c and SJL mice. Our results indicate that regulatory T cells, as well as regulatory ontogenetic processes, are not responsible for the r lambda 1 lo phenotype. In addition, limiting dilution analyses revealed that the number of lipopolysaccharide-sensitive precursors of lambda 1-secreting B cells was similar in the splenocytes of the two strains of mice tested. The quantity of lambda 1 molecules produced by a B cell clone, however, was found to be lower in SJL than in BALB/c mice. As the level of lambda 1 mRNA is greatly reduced in lipopolysaccharide blasts of SJL mice, as compared to the mRNA detected in BALB/c blasts, we conclude that the impairment responsible for the r lambda 1lo phenotype is probably transcriptional. We tentatively propose that sequences 5' to the C lambda 1 region are defective in their capacity to enhance the lambda 1 transcripts in SJL mice.

Immunochemical characterization of the specificities of two human monoclonal IgM's reacting with chondroitin sulfates

We have studied the specificities of two human monoclonal, IgM containing sera, s/IgMMAC and s/IgMFIS, from patients with polyneuropathy. s/IgMMAC precipitates only with chondroitin sulfate C and not with A and B whereas s/IgMFIS is precipitated by chondroitins A, B (dermatan sulfate), and C. Inhibition assays using 2-acetamido-2-deoxy-3-O-(4-deoxy-beta-L-threo-hex-4-enopyranosyluroni c acid)-D-galactose and its 6- and 4-sulfate derivatives showed that the disaccharide 6-sulfate was the best inhibitor of precipitation of s/IgMMAC by chondroitin sulfate C, and the disaccharide 4-sulfate the best inhibitor of precipitation of s/IgMFIS by either chondroitin sulfates C or B. The nonsulfated disaccharide was a good inhibitor in each instance. D-Glucose 6-sulfate, Na2SO4, several sugar phosphates, and phosphate buffer also inhibited but to different extents with the s/IgMMAC and s/IgMFIS. All studies were carried out in 0.15M NaCl. The data indicate that both monoclonal proteins are antibodies comparable to the phosphorylcholine-binding myeloma proteins, and that the reactions show specificities above and beyond charge effects. The relation of various cross-reacting macromolecules to the monoclonal antibody was studied by diffusion in gels.