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U Krawinkel

Publications and source records attributed to U Krawinkel.

At least 55 records · Page 3Linked to original sources
PubMed1987

Directed Ig class switch recombination in activated murine B cells.

Immunoglobulin class switch recombination occurs at frequencies of up to 10%/cell/generation in activated murine B-lymphocytes. We analysed cH gene rearrangements and switch recombinations from active and inactive IgH loci of B-cells activated in various ways and immortalized by cell fusion. Although about half of the IgM+ cells show rearrangement of c mu genes, the deletion of c mu is a rare event. Half of the IgG3+ and IgG1+ cells show rearrangement of c mu genes on the inactive IgH locus and the other half of the IgG+ cells have deleted c mu from both IgH loci by switch recombination. This recombination is directed to the same switch regions on both IgH loci in 60-80% of all cases. Interleukin 4 may play a critical role in programming murine B-lymphocytes for specific switch recombination.

Amino Acid Sequence↗
PubMed1987

Evolution of pseudogenes in the immunoglobulin VH-gene family of the mouse.

A quantitative analysis of the complexity of the J558 VH-gene family in the mouse immunoglobulin heavy chain (Igh) gene locus has been performed. Considerable variations in the degree of complexity are observed in various Igh haplotypes derived from laboratory mice and wild mice. The BALB/c strain shows the highest degree of complexity of the J558 VH-gene family when all mice are compared. Multiple gene duplications seem to have occurred in the BALB/c-derived J558 VH-gene family less than 1-2 million years ago. This dating is supported by the divergence in coding and flanking regions of three strongly homologous VH-region genes. Two of these genes were generated by the duplication of a pseudogene about 1.5 X 10(5) years ago. A recent expansion of the J558 VH-gene family and therefore little time for evolutionary drift may explain why most of the pseudogenes in this family exhibit a largely intact structure. We also describe two VH-region genes which represent older pseudogenes in states of progressive disintegration.

Amino Acid Sequence↗
PubMed1986

Palindromic sequences are associated with sites of DNA breakage during gene conversion.

Gene conversion is a recombinatorial mechanism which transfers genetic information from a donor into a recipient gene. A case of gene conversion between immunoglobulin VH region genes was analysed and palindromic sequences were found to be located near to the left recombinatorial breakpoint, which also is flanked by a direct repeat sequence. We performed a computer search for palindromes and direct repeats in the published sequences of eucaryotic genes which had been involved in gene conversion. In these sequences, the palindrome with the best or second best quality is located near to a breakpoint of recombination. A correlation of recombination breakpoints with direct repeats was not observed. This suggests that gene conversion is promoted by palindromic sequences.

Animals↗
PubMed1985

VH-gene expression in murine lipopolysaccharide blasts distributes over the nine known VH-gene groups and may be random.

VH-gene expression in hybridomas derived from lipopolysaccharide-activated B cells was analyzed. Isolated cytoplasmic RNA was hybridized to probes representing the 9 known VH-gene groups or subjected to mRNA sequencing. In the collection of hybridomas VH genes of all 9 groups are expressed at frequencies which in most correlate reasonably well with the relative complexities of the groups. In 51 out of 54 RNA samples VH-gene transcripts could be identified and corresponded to one of the known VH-gene groups. It therefore appears that the latter essentially represent the VH-gene cluster of the mouse.

Animals↗
PubMed1985

Members of novel VH gene families are found in VDJ regions of polyclonally activated B-lymphocytes.

Four potentially productive and two non-productive VDJ gene segments were isolated from the DNA of mouse B-lymphocytes which had been polyclonally activated by bacterial lipopolysaccharide (LPS). Three VDJ regions exhibit VH genes which stem from two novel VH gene families. The complexity of these families is 5-9 genes. One of the non-productive VDJ regions exhibits a D segment which may have been generated by joining of two DSP2 segments. Both non-productive VDJ regions appear to contain rearranged pseudo VH genes. Three potential somatic mutations distributed over two productive VDJ regions are observed.

Animals↗
PubMed1984

Analysis of immunoglobulin heavy chain V-region genes belonging to the V NP-gene family.

A method was devised to clone immunoglobulin VH-region genes located on selected restriction fragments from genomic DNA directly into M13 vectors for subsequent nucleotide sequence analysis. Ten recombinant M13 clones representing four so far unknown VH-region genes of the VNP-gene family have been analysed. Sequence comparison shows that these genes are closely related to other VH-genes of the VNP gene family. One of the VH-genes exhibits a so far unobserved unusual length of 100 2/3 codons and appears to be functional. Analysis of the variation of the isolated VH-genes suggests that framework and complementarity determining regions are exposed to separate types of selective pressures.

Animals↗
PubMed1983

Affinity-purified antigen-specific products produced by T cells share epitopes recognized by heterologous antisera raised against several different antigen-specific products from T cells.

Heterologous antisera to murine or rat T-cell antigen-binding molecules (T-ABM) were raised in rabbits or sheep. The T-ABM used for immunization were purified by affinity for antigen and did not bear known immunoglobulin isotypes. T-ABM and anti-T-ABM were raised in three separate laboratories. Antisera to T-ABM were exchanged and tested for binding to T-ABM in three separate laboratories. Thus antisera to at least three distinct T-ABM were tested directly for binding to T-ABM or by adsorption of biological activity. Rabbit antisera to murine trinitrophenol (TNP)-specific T-ABM or rat AgB-specific T-ABM bound both murine or rat T-ABM, indicating evolutionary conservation of T-ABM. Similar results were found with sheep antisera to murine T-ABM. In addition, all heterologous anti-T-ABM antisera used bound murine T-ABM specific for TNP, 4-hydroxy-3-nitrophenyl acetate (NP), SRBC, or T-cell membrane proteins with similar structure. Thus, there is a commonality of antigenic determinants between various T-ABM and T-cell membrane homologues which may be T-cell surface receptors for foreign antigen.

Animals↗
PubMed1983

Recombination between antibody heavy chain variable-region genes: evidence for gene conversion.

The murine hybridoma line B1-8.delta 1 secretes monoclonal IgD lambda 1 antibodies specific for the hapten (4-hydroxy-3-nitrophenyl)acetyl (NP). The variable (V) region of these antibodies is defined by a characteristic pattern of idiotopes. A spontaneous V-region variant (B1-8.V1) with altered idiotope pattern was selected. The structural variation is confined to the V region of the heavy chain. It was shown previously that the variant V region is encoded by a gene that was generated by a crossover between the rearranged VDJ gene of the wild type (B1-8.delta 1) and a neighboring germ-line VH gene. In the present study the nucleotide sequence of coding and flanking regions of the VH gene expressed in variant B1-8.V1 was determined. Wild-type and variant VH genes differ at 15 positions in a region between leader sequence and codon 66. The sequence of the region carrying the substitutions is identical to the sequence of the corresponding region in a neighboring germ-line VH gene. This implies that the variant VH gene was generated by a mechanism of recombination more complicated than single crossover. Gene conversion as the mechanism of the recombination is discussed.

Animals↗
PubMed1982

Comparison of the hinge-coding segments in human immunoglobulin gamma heavy chain genes and the linkage of the gamma 2 and gamma 4 subclass genes.

The genes for the human immunoglobulin heavy chain constant region subclasses have been examined in clones isolated from a phage library containing human genomic DNA. Nucleotide sequencing and restriction enzyme mapping show that the CH1, hinge, CH2, and CH3 domains are present as distinct genetic elements separated by short intervening sequences in these genes: the gamma 3 gene is unique amongst these genes in that it possesses four separate hinge-coding segments. A further gamma gene has been identified which does not correspond to a known human gamma protein: this gene contains a hinge related to the first hinge of the gamma 3 gene and may represent an inactive or pseudo gamma gene. Comparison of a number of overlapping clones containing gamma 2 and gamma 4 genes shows that they are separated in human DNA by approximately 19 kb and that the gamma 2 gene is located upstream of gamma 4. Both genes (order 5'C gamma 2-C gamma 4-3') are orientated in the same direction of transcription.

Amino Acid Sequence↗
PubMed1980

Antigen-specific receptor molecules isolated from murine T lymphocytes.

Hapten-specific receptor material can be isolated from sensitized murine T and B lymphocytes by the use of hapten-coupled nylon discs. The structural element shared between T and B cell receptors is the variable region of immunoglobulin heavy chains (VH), while known constant immunoglobulin domains appear not to be part of the T cell receptor molecule. The rules governing VH expression (i.e. NPb-idiotype expression) in the B and the T cell compartments are, however, different. Allotype-linked VH (idiotype) expression on T cell molecules was used in genetic reconstitution experiments to prove that the material under study is an endogenous T cell product. With the data available it seems reasonable to view the T cell molecules as representing surface receptors for antigen although this point needs further investigation.

Animals↗
PubMed1978

Isolated hapten-binding receptors of sensitized lymphocytes. III. Evidence for idiotypic restriction of T-cell receptors.

The primary antibody response of C57BL/6 mice to the 4-hydroxy-3-nitrophenylacetyl (NP) hapten is restricted to antibody molecules expressing the NPb idiotype. This idiotype is a genetic marker for V genes in the heavy chain linkage group. In the secondary response, the frequency of NPb idiotype-positive molecules within the antibody population drops to very low values. Accordingly, isolated NP binding receptors from NP-sensitized B lymphocytes are largely devoid of this idiotype. In contrast, the NPb idiotype is expressed on the majority of the receptor fractions which we consider T-cell derived. This finding suggests that the antigen receptors of T lymphocytes may be restricted to the expression of major (germ-line encoded?) heavy chain idiotypes.

Animals↗
PubMed1977

Isolated hapten-binding receptors of sensitized lymphocytes. II. Receptors from nylon wool-enriched rabbit T lymphocytes lack serological determinants of immunoglobulin constant domains but carry the A locus allotypic markers.

Hapten-binding receptor material was isolated from sensitized rabbit lymphocytes by a method described previously for murine receptor material. The material was separated into a fraction expressing immunoglobulin determinants (anti-Ig+ fraction) and a fraction lacking known class and type-specific determinants of Ig constant domains (anti-Ig- fraction). We present evidence in support of the notion that--in analogy to the mouse system--the anti-Ig+ fraction is B-cell-derived, whereas the anti-Ig- fraction originates from T lymphocytes. Receptors of the anti-Ig- phenotype are found to express a locus allotypic determinants and, thus, appear to carry variable portions of immunoglobulin heavy chains.

Animals↗
PubMed1977

On the structure of the T-cell receptor for antigen.

Antigen-binding receptors of T lymphocytes were analyzed in two different ways. First, the idiotypic properties of T helper cells are studied using anti-idiotypic antisera prepared against isolated antibodies specific for A-CHO. These anti-idiotypic antisera are defined by immunogenetic and immunochemical means with respect to their reactivity with heavy- or light-chain-associated idiotypic determinants. Second, antigen-binding receptors are isolated from enriched T-and B-lymphocyte preparations and compared with respect to their reactivity with antigen and with class- or allotype-specific anti-Ig antisera. The results provide an incomplete picture of the T-cell receptor which shares with antibodies the variable region of the heavy chain but probably no other variable or constant portion.

Animals↗