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B K Birshtein

Publications and source records attributed to B K Birshtein.

At least 55 records · Page 3Linked to original sources
PubMed1983

Determinants recognized by murine rheumatoid factors: molecular localization using a panel of mouse myeloma variant immunoglobulins.

The structures recognized by monoclonal anti-IgG1 rheumatoid factors (RF) were localized by testing their reactivity with mutant immunoglobulins carrying gamma 1 chains that lacked either the CH1 or the CH3 domains. While optimal binding was observed in the absence of CH1, deletion of CH3 completely abolished the reactivity of all but one of the 71 monoclonal RF tested. Similar experiments were carried out with IgG2a- and IgG2b-specific RF by using variant immunoglobulins carrying various hybrid gamma 2a-gamma 2b heavy chains. It was found that both the polyclonal RF produced by autoimmune strains, MRL/MpJ-lpr and NZB/BinJ, and most of the monoclonal RF derived from normal strains, BALB/c, C57Bl/6, and 129/Sv, were directed against determinants located in a segment spanning the C-terminal 8 residues of the CH2 domain and the complete CH3 domain.

Animals↗
PubMed1983

Hybrid gamma 2b-gamma 2a genes expressed in myeloma variants: evidence for homologous recombination.

The expressed immunoglobulin heavy chain genes of five gamma 2b-gamma 2a hybrid chain-producing variants of the mouse myeloma MPC-11 (gamma 2b, kappa) have been characterized by genomic Southern blot analysis. Results show that a hybrid gamma 2b-gamma 2a gene was formed in each variant by recombination between the expressed gamma 2b gene of MPC-11 and a gamma 2a gene. The recombination sites are within regions of marked homology between gamma 2b and gamma 2a genes: at least three and probably four variants show gamma 2b-gamma 2a recombination within the heavy chain constant region 2 (CH2) domain, while the fifth has its recombination site between the penultimate nucleotide of CH1 and the eighth nucleotide of the hinge. An unexpected finding is that the hybrid heavy chain-producing variants fall into two subgroups based on their use of different gamma 2a gene forms in hybrid gene formation. This result leads to the speculation that either a tandem gamma 2a gene duplication was present in MPC-11 prior to variant generation or mitotic recombination between chromosomes occurred in the generation of one variant subgroup. The similarity of hybrid gene formation in MPC-11 variants to that apparently responsible for concerted evolution within multigene families and hybrid protein expression in various individuals is noted, and the possible relationship between hybrid gene formation and the heavy chain class switch is discussed.

Animals↗
PubMed1983

Localization of murine Igh-1a allotypic determinants by using a panel of mouse myeloma variant immunoglobulins.

A number of monoclonal antibodies are available that are reactive with distinct mouse immunoglobulin allotypic determinants. By determining which ones are present on a panel of hybrid IgG2b-IgG2a immunoglobulins, we have localized some of the allotypic determinants present on the IgG2a heavy chain of the "a" allotype (Igh-1a proteins). In particular, one group of determinants--Ig(1a)9.8 (20.6B8), 17.2 (20.19.2), and 14.4 (21.74.4)--has been placed in the CH2 domain. A second group--Ig(1a)8.3 (20.8.3), 21.2 (20.11.2), and 15.3 (21.66.3)--is located in a segment spanning the C terminal 8 residues of the CH2 domain and the complete CH3 domain.

Animals↗
PubMed1982

DNA rearrangements in MPC-11 immunoglobulin heavy chain class-switch variants.

Immunoglobulin heavy chain class switching has been observed in vitro. In the IgG2b-producing MPC-11 mouse myeloma cell line, IgG2a-producing cells arise at a high frequency. In some cases, switch variants producing normal-sized (Mr 55,000) gamma 2a heavy chains have arisen spontaneously from a mutagen-induced "intermediate" (ICR 9.7.1) that produces an unusually large (Mr 75,000) heavy chain. Other switch variants have been isolated directly from the parent cell line. The expressed and unexpressed gamma 2b genes of MPC-11 can be distinguished in restriction endonuclease digests of total genomic DNA so that DNA rearrangements detected in MPC-11 variants can be directly associated with one or the other of these two genes. We describe here DNA rearrangements occurring on the expressed heavy chain chromosome of several MPC-11 gamma 2a switch variants and on the expressed chromosome of the ICR 9.7.1 intermediate. Our data indicate that all of these variants express the parental heavy chain variable region (VH) gene, supporting previous protein studies. We provide mapping data for the expressed gene of both ICR 9.7.1 and one of the IgG2a-producing variant cell lines (ICR 9.9.2.1) derived from it and discuss the advantages of an in vitro switching system for examining the dynamics of the immunoglobulin heavy chain class switch.

Animals↗
PubMed1982

Effects of immunoglobulin structure on Fc receptor binding: a mouse myeloma variant immunoglobulin with a gamma 2b-gamma 2a hybrid heavy chain having a complete gamma 2a Fc region fails to bind to gamma 2a Fc receptors on mouse macrophages.

We report here the primary structure of an immunoglobulin heavy chain synthesized by ICR 16, a variant of the MPC 11 mouse myeloma cell line. The ICR 16 heavy chain is a gamma 2b-gamma 2a hybrid, consisting of the CH1 domain of gamma 2b and the hinge, CH2 and CH3 domains of gamma 2a subclasses. The genetic mechanism by which ICR 16 occurred may be recombination, based on homologies in both coding and intervening sequences in gamma 2b and gamma 2a constant region genes. Although the Fc fragment of ICR 16 is completely gamma 2a-like and has been shown to bind to gamma 2a Fc receptors on mouse macrophages, the intact H2L2 molecules is unable to do so. Such an observation underscores the crucial role that conformation may play in the ability of immunoglobulins to carry out biologic functions.

Amino Acid Sequence↗
PubMed1979

Genetic mechanism accounting for precise immunoglobulin domain deletion in a variant of MPC 11 myeloma cells.

A variant of the MPC 11 cell line, M 311, produces a short immunoglobulin heavy chain. When compared with the parental gamma 2b heavy chain, M 311 was found to have a carboxyl terminal deletion comprising the CH3 domain. The COOH-terminal cyanogen bromide (CNBr) cleavage fragment of M 311 is identical to a corresponding segment ofa parental heavy chain CNBr fragment, with the exception of a substitution of asparagine for lysine at the COOH-terminal residue. This observation enabled prediction of both the parental DNA sequence in this region and the genetic mechanism which generated the variant, a frameshift followed by premature termination. This hypothesis is supported by studies of the DNA sequence of the MPC 11 gamma 2b constant region gene.

Animals↗
PubMed1979

Site of binding of mouse IgG2b to the Fc receptor on mouse macrophages.

Three mouse immunoglobulins with altered heavy chains have been used to study the specificity of the mouse IgG2b Fc receptor on mouse macrophages. These immunoglobulins were synthesized by variant clones derived from the MPC 11, IgG2b-producing mouse myeloma cell line. One variant, whose Fc receptor. A second variant, which makes a short heavy chain lacking the CH3 domain, binds specifically to the IgG2b Fc receptor. The third variant makes a hybrid IgG2b-IgG2a heavy chain whose CH3 domain is enterely IgG2a-like and binds to both IgG2a and IgG2b Fc receptors. These data suggest that the binding of mouse IgG2b immunoglobulins to the mouse macrophage Fc receptor involves a site within the CH2 domain and indicate that immunoglobulins with altered heavy chains are a useful tool to probe Fc receptors.

Animals↗
PubMed1978

An IgG2a-producing variant of an IgG2b-producing mouse myeloma cell line. Structural studies on the Fc region of parent and variant heavy chains.

The IgG2b-producing MPC 11 mouse myeloma cell line has yielded a number of variants which synthesize heavy chains characteristic of a different immunoglobulin subclass, IgG2a, as previously shown by serology, peptide maps, and assembly profiles. We have studied the Fc regions of the IgG2a protein synthesized by one variant, ICR 9.9.2.1, and of the IgG2b protein synthesized by MPC 11 and compared them to MOPC 173, an IgG2a protein of known sequence. We analyzed the Fc regions of the three immunoglobulins by several analytical techniques, such as immunoelectrophoresis of papain digests, NaDodSo4-polyacrylamide gel electrophoresis analyses of Fc CNBr fragments, and comparative ion-exchange chromatography of radiolabeled tryptic and chymotryptic Fc peptides. In addition, Fc CNBr fragments of the variant gamma2a and MPC 11 gamma2b molecules were isolated and subjected to amino acid analysis and partial sequence determination. From these data, we concluded that the Fc fragment of ICR 9.9.2.1 is most probably identical to that of MOPC 173 and different from the parental gamma2b Fc fragment. A number of residue positions which discriminate between gamma2b and gamma2a sequences are described. In two of three segments sequenced, gamma2b and gamma2a molecules share more identical residues than either shares with another mouse subclass, gamma1.

Amino Acid Sequence↗
PubMed1978

IgG2a-producing variants of an IgG2b-producing mouse myeloma cell line.

12 variant cell lines producing an IgG2a (kappa) immunoglobulin derived via different routes from the IgG2b (kappa) synthesizing MPC 11 were studied. These variants all have the parental MPC 11 idiotype as shown by a radioimmunoassay. A comparison of the variants by charge, peptide maps, and assembly patterns has shown that most of them differ from one another, and some can be grouped. One group consists of three primary variants generated with two mutagenic agents: these three have almost indistinguishable peptide maps. Two other primary variants which arose in a similar fashion differ markedly from each other and from this group. A second group is comprised of the four secondary variants which arose from two short heavy chain producing primary variants. Other secondary variants and the one spontaneously arising variant cannot be grouped. Possible genetic mechanisms such as translocation, expression of previously silent genes and recombination are discussed.

Cell Line↗
PubMed1975

Variants of a mouse myeloma cell line that synthesize immunoglobulin heavy chains having an altered serotype.

Cells of the MPC-11 mouse myeloma cell line, which produces an IgG2b immunoglobulin, were subjected to mutagenesis with Melphalan or with ICR-191, after which they were cloned in soft agar. Approximately 0.5 percent of the clones produced altered heavy chains that: (i) were the same size as or larger than the parent; (ii) no longer recognized by antibody specific for the parent gamma2b subclass; (iv) were recognized by antibody against the Fab (NH2-terminal half) of the parental immunoglobulin, but lacked some of the antigenic determinants of the Fc (COOH-terminal half) of the heavy chain; (v) lacked many of the tryptic/chymotryptic peptides found in the parent; (vi) contained tryptic/chymotryptic peptides that were not present in the parent but were present in an unrelated gamma2a myeloma heavy chain; and (vii) assembled with light chains by a pathway typical of IgG2a myelomas.

Amino Acid Sequence↗
PubMed1974

Variants of mouse myeloma cells that produce short immunoglobulin heavy chains.

After mutagenesis of cultured mouse myeloma cells with ICR 191 or Melphalan, variant clones were isolated that synthesized immunoglobulin heavy chains shorter than those produced by the parent. These variants fell into two phenotypes, based on the size, serology, and pattern of assembly of the heavy chain. Variant chains of both types no longer reacted with antisera directed either against the Fc (C-terminal half of the heavy chains) or subclass-specific IgG(2b) determinants. Comparative ion exchange chromatography of tryptic-chymotryptic peptides confirmed that the variant heavy chains differed structurally from those of the parent and from each other. A conversion from one phenotype to the other has been observed.

Acridines↗
PubMed1973

Mutations in immunoglobulin-producing mouse myeloma cells.

Three mouse myeloma cell lines were cloned in soft agar and screened by an antiserum overlay method for variants defective in secretion of the myeloma protein. Variants that had lost the capacity to synthesize heavy chains arose spontaneously at a high rate of about 10(-3) per cell per generation. Such variants lost the capacity to produce light chains at a similarly high rate. After cells were treated with the acridine half mustard ICR-191, variants occurred with an even higher incidence, and some of these synthesized heavy chains differing from that of the parent.

Acridines↗