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Biomedical subjects

A S Kelus

Publications and source records attributed to A S Kelus.

At least 19 recordsLinked to original sources
PubMed1991

Is there really a "lack of natural tolerance to allotypic gamma-globulins in rabbits"?

We present data of extended studies on the possibility of maternally derived allotype Ig inducing a state of natural immunological tolerance to a non-inherited allotype in the offspring. Rabbits homozygous at the a locus, encoding allotypes in the variable region of immunoglobulin heavy chains, and rabbits homozygous at the unliked b locus, encoding allotypes of the constant region of kappa 1 chains, were immunized at the age of 2 months against the non-inherited allotype of their heterozygous mothers to which they had been exposed in utero and in early life. As control, we immunized rabbits of the same Ig phenotype but born to homozygous mothers, and therefore not exposed to that allotype. Immunization was done in a3/a3 offspring of either a1/a3 or a3/a3 mothers, by injecting a 1 IgG, and in b6/b6 offspring of b4/b6 or b6/b6 mothers, by injecting b4 IgG. The IgG was injected either in a soluble form or emulsified in adjuvant. Injection of soluble IgG elicited only a low response, if any, revealing no differences between the various groups. All rabbits responded upon immunization with IgG in adjuvant. We have not found any good evidence for natural tolerance to a non-inherited allotype, although progeny of a1/a3 mothers had slightly decreased responses to a1. On the contrary, progeny of b4/b6 mothers responded even better than offspring of b6/b6 mothers, upon such immunization with b4. To induce tolerance experimentally, we injected newborn rabbits, either from heterozygous a1/a3 or from homozygous a3/a3 mothers, with a1 serum or IgG. Newborn of heterozygous b4/b6 or of homozygous b6/b6 mothers were injected with b4 serum or IgG in the same way. Such treatment resulted in partial tolerance to each allotype. In an attempt to amplify the tolerizing effect of the maternal a1 Ig, we injected newborn rabbits of a1/a3 mothers with the serum of their mother. The response upon subsequent immunization with a1 allotype of another individual did not differ significantly from the response of control rabbits. The response was much poorer when rabbits were injected with nonmaternal tolerogen at birth, and when the same Ig preparation was used as immunogen. In a control experiment, neonatal injection of xenogeneic proteins, human IgG or bovine serum albumin, clearly resulted in tolerance. We speculate that tolerance to allotypes is established in the T cell repertoire only but bypassed by recognition of idiotypic determinants on antigen molecules by helper T cells, which trigger anti-allotype antibody formation by allotype-specific B cells. The end result of it is a lack of natural tolerance.

Animals↗
PubMed1991

Molecular analysis of recombination sites within the immunoglobulin heavy chain locus of the rabbit.

Previously, recombinations involving genes of the rabbit immunoglobulin heavy chain locus have been documented serologically. These data indicated that the sites at which the causative recombination events occurred could have been anywhere from within the VH gene cluster up to, or 3' of, C mu. Since these sites could not be localized further by serological methods, we attempted to do this using techniques of molecular biology. DNAs from homozygous recombinant rabbits and from the appropriate non-recombinant parental haplotypes were characterized using Southern blots hybridized with a panel of probes derived from cloned regions of the rabbit immunoglobulin heavy chain gene complex. In all three recombinants, the site was downstream of the entire VH cluster and upstream of the JH cluster within an approximately 50 kilobase (kb) region containing expanses of repetitive-sequence DNA as well as DH genes. DH-specific probes further showed that in two of the recombinants, the recombination appears to have occurred within or 5' of DH1 and 5' of DH2 genes; in the third it occurred 3' of the DH2 genes but at least approximately 5 kb 5' of the JH region.

Animals↗
PubMed1991

Is there a high rate of mitotic recombination between the loci encoding immunoglobulin VH and CH regions in gonial cells?

Rabbit sera from approximately 6000 offspring of matings informative for recombination at the immunoglobulin (Ig) heavy chain locus were tested with allotype antisera by double diffusion in gel. Seven recombinants were found, R1K-R7K, and in every case the recombinational event had taken place in the male parent. Two single males each fathered two recombinant offspring: R2K, R4K and R5K, R6K. Four further recombinants, reported from other laboratories as well as two new, as yet not fully documented recombinants in our laboratory, also occurred in the male parent. The recombinational events either separated the a locus which encodes the VH region of Ig, from the loci encoding its CH region or separated a-ms from the remaining linked loci d-e-f-g. The recombination frequency is 7/6142, approximately 0.1%. Our findings suggests that the recombinations took place in mitotic divisions during spermatogenesis. This work is the first evidence of gonial crossing-over in a mammal.

Animals↗
PubMed1990

Limited number of immunoglobulin VH regions expressed in the mutant rabbit "Alicia".

A unique feature of rabbit Ig is the presence of VH region allotypic specificities. In normal rabbits, more than 80% of circulating immunoglobulin molecules bear the VHa allotypic specificities, al, a2 or a3; the remaining 10% to 20% of immunoglobulin molecules lack VHa allotypic specificities and are designated VHa-. A mutant rabbit designated Alicia, in contrast, has predominantly serum immunoglobulin molecules that lack the VHa allotypic specificities (Kelus and Weiss, Proc. Natl. Acad. Sci. USA 1986. 83: 4883). To study the nature and molecular complexity of VHa- molecules, we cloned and determined the nucleotide sequence of seven cDNA prepared from splenic RNA of an Alicia rabbit. Six of the clones appeared to encode VHa- molecules; the framework regions encoded by these clones were remarkably similar to each other, each having an unusual insertion of four amino acids at position 10. This insertion of four amino acids has been seen in only 2 of 54 sequenced rabbit VH genes. The similarity of the sequences of the six VHa- clones to each other and their dissimilarity to most other VH genes leads us to suggest that the VHa- molecules in Alicia rabbits are derived predominantly from one or a small number of very similar VH genes. Such preferential utilization of a small number of VH genes may explain the allelic inheritance of VH allotypes.

Amino Acid Sequence↗
PubMed1990

Altered phenotypic expression of immunoglobulin heavy-chain variable-region (VH) genes in Alicia rabbits probably reflects a small deletion in the VH genes closest to the joining region.

Rabbits of the Alicia strain have a mutation (ali) that segregates with the immunoglobulin heavy-chain (lgh) locus and has a cis effect upon the expression of heavy-chain variable-region (VH) genes encoding the a2 allotype. In heterozygous a1/ali or a3/ali rabbits, serum immunoglobulins are almost entirely the products of the normal a1 or a3 allele and only traces of a2 immunoglobulin are detectable. Adult homozygous ali/ali rabbits likewise have normal immunoglobulin levels resulting from increased production of a-negative immunoglobulins and some residual ability to produce the a2 allotype. By contrast, the majority of the immunoglobulins of wild-type a2 rabbits are a2-positive and only a small percentage are a-negative. Genomic DNAs from homozygous mutant and wild-type animals were indistinguishable by Southern analyses using a variety of restriction enzyme digests and lgh probes. However, when digests with infrequently cutting enzymes were analyzed by transverse alternating-field electrophoresis, the ali DNA fragments were 10-15 kilobases smaller than the wild type. These fragments hybridized to probes both for VH and for a region of DNA a few kilobases downstream of the VH genes nearest the joining region. We suggest that this relatively small deletion affects a segment containing 3' VH genes with important regulatory functions, the loss of which leads to the ali phenotype. These results, and the fact that the 3' VH genes rearrange early in B-cell development, indicate that the 3' end of the VH locus probably plays a key role in regulation of VH gene expression.

Animals↗
PubMed1986

Mutation affecting the expression of immunoglobulin variable regions in the rabbit.

We have found a variant of the allotype allele a2 in the rabbit, which presumably arose by mutation, that segregates as expected for an allele at the a locus. This allele is called "ali" and the corresponding rabbit strain is called "Alicia." In heterozygous animals (ali/a1 and ali/a3) the concentration of a2 molecules is lower by a factor of 1000 than in standard a2/a2 homozygotes. In homozygous ali/ali individuals the a2 concentration varies with age--i.e., very low in young rabbits and higher in older ones--but it never reaches normal levels. The low level of a2 is compensated by increased amounts of a-negative molecules. Southern blot analysis did not reveal any gross changes in the intron between JH and C mu (joining region of immunoglobulin heavy chain and constant region of immunoglobulin mu chain) or in the number of VH gene segments encoding a locus specificities. We suggest that the ali phenotype is due to a mutation in a control element.

Animals↗
PubMed1985

Transfer of fresh and frozen-thawed rabbit embryos to produce live young.

Live rabbits for immunological experiments were produced by transfer of fresh or frozen-thawed embryos. The transfer of 505 fresh embryos and 55 frozen-thawed embryos resulted in 141 young born alive, 81 of which lived between several months and several years. The control group consisted of 55 litters from natural matings. About 70% of the live-born rabbits of natural mating and 55% of the young delivered by embryo transfer survived for more than eight weeks. Average litter sizes were 5.7, 3.7 and 2.2 for naturally mated females, fresh embryo transfer recipients, and frozen-thawed recipients, respectively.

Animals↗
PubMed1984

Genetics and expression of kappa-type light chains in Basilea rabbits.

In contrast to rabbits of b4, b5, b6, and b9 allotypes whose serum immunoglobulins (Igs) are predominantly composed of kappa-type light chains, rabbits of the mutant Basilea strain have serum Igs that are largely of lambda type. We prepared several antisera that recognized a minor K2 (bas) light chain that is produced by Basilea rabbits. With these antisera we identified the K2 (bas) isotype in the serum of the original b9/b9 male rabbit whose offspring displayed the Basilea mutant phenotype. It was present in one half of his nonmutant offspring which inherited b9 from him and another b allotype from their mothers. Breeding was conducted both in Basel and at the NIH to develop and maintain colonies of mutant Basilea strain rabbits. The data obtained during colony development confirm that the trait of expression of the bas allotype maps to the same genetic region (b locus) that is known to control the allelic b allotypes b4, b5, b6 and b9. Homozygotes or heterozygotes of b4, b5 or b6 allotype (bb/bb) were mated with homozygous bbas / bbas rabbits to produce F1s , and then F2s as well as progeny of backcrosses to both homozygous parental types (bb/bb and bbas / bbas ) were produced. The bas allotype segregates as an allele (or pseudoallele ) at the b locus although there was a deficiency in recovery of homozygous bas offspring in both the F2 and backcross matings to bbas / bbas parental type in the NIH colony. This selective deficiency may reflect a deleterious effect on survival of homozygous bas progeny.

Animals↗
PubMed1982

Allotypes in Basilea rabbits.

Basilea rabbits produce immunoglobulin molecules, practically all of which have lambda light chains rather than kappa chains. This variant strain was derived form a homozygous (b9/b9) male. Sensitive serological methods revealed that at least some homozygous bas/bas individuals possess traces (about 100 ng/ml) of b9 molecules. This level usually increases to almost 1 microgram/ml upon hyperimmunization with pneumococcal or streptococcal vaccines. One exceptional rabbit, with 50 micrograms/ml of b9 molecules, was found. In spite of the presence of b9 molecules in early pre-immune bleeds, homozygous bas/bas rabbits produce strong anti-b9 antibodies; i.e., they are capable of making autoantibodies. These anti-b9 allotypic antisera were not distinguishable by our methods from routinely produced anti-b9.

Animals↗
PubMed1978

Allelic exclusion in the B lineage cells of the rabbit.

Allelic exclusion of the K polypeptide chain allotypes b4 and b5 of the rabbit exists for the immunoglobulins of almost all plasma cells and of most mature small B lymphocytes. However, both these alleles are expressed simultaneously in rare plasma cells and in an usually large fraction of the lymphoid cells of the bone marrow. Our experiments support the idea that such bone marrow B lineage cells do not always show allelic exclusion.

Alleles↗
PubMed1978

Maternal allotype dominance and allelic exclusion in the B lineage cells of the newborn rabbit.

Newborn rabbits from parents which differ at the b allotype locus (kappa chain), show a strong maternal allotype dominance, especially in the bone marrow. This concerns not only the membrane but also the cytoplasm, and it cannot be simply due to a passive uptake of maternal immunoglobulins. The spleen precedes the bone marrow for a high level of expression of the paternal allotype. In the thymus, cells which contain cytoplasmic immunoglobulin are found at low frequency, but their absolute number represent a substantial contribution to the B lineage cell pool. A small proportion of such thymus cells do not show allelic exclusion of kappa chain allotypes.

Alleles↗
PubMed1977

Antibody response to the streptococcal group A-variant polysaccharide in BASILEA rabbits lacking kappa-polypeptide chains.

Rabbits from a variant strain called BASILEA, in which homozygotes express only lambda-type chains and heterozygotes have normal kappa/lambda ratios, were hyperimmunized with a streptococcal group A variant vaccine. Homozygotes (bas/bas) produced antibodies with lambda-chains, heterozygotes, however, produced predominantly antibodies with kappa-chains. The incidence of restricted high responders in the BASILEA strain was high; it was probably introduced by the original mutant rather than by the loss of kappa-chains (founder effect). The degree of heterogeneity of homozygotes is similar to the heterogeneity of heterozygotes, and to that of rabbits expressing kappa-chains. This suggests that in the rabbit, the repertoire of lambda-chain genes is of similar size to that of kappa-chain genes.

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

Peptide mapping of the lambda-like chains of the BASILEA rabbits.

The recently established mutant strain of rabbits, named BASILEA, lacks the k polypeptide L-chain which is replaced by a lambda-like type (bas). This is evident from the amino acid composition and peptide maps of the bas L-chain when compared to the L-chains of the rabbits suppressed for the expression of the b locus allotypes.

Amino Acids↗
PubMed1973

Idiotypic specificity of rabbit antibodies to streptococcal group polysaccharides.

Anti-idiotypic antisera against six restricted rabbit streptococcal group specific antibodies have been raised in rabbits matched for allotypes. All these antisera reacted specifically with their homologous idiotypes on double-diffusion tests in agarose gel. In addition, they showed a high incidence of cross-specificities with group-specific hyperimmune sera induced in both closely related and unrelated individuals. These precipitating cross-specificities could be explained for two systems by the interference of rheumatoid factor. Two idiotypic antibody systems have been analyzed in detail; these were restricted antibodies produced in a father and in one of his offspring. The methods employed included binding inhibition of radio-labeled homologous Fab fragments and hemagglutination inhibition with homologous idiotypic coat. The data demonstrated that only related rabbits produced, besides non-cross-reacting antibodies, idiotypically similar antibodies raised to the same antigen. About one-third of the cross-reactive idiotypes showed binding inhibition between 31 and 92%. Inhibition of binding above 50% in the paternal idiotypic system was only achieved by one offspring antibody whereas the F(1) progeny idiotypic system was inhibited to this extent by seven antibodies of related rabbits. In contrast, 87.5% and 91.7% of antibodies of unrelated rabbits were less than 20% inhibitory. Within this study two idiotypically identical antibodies have not been found. This implies that A-variant-specific antibodies of related rabbits which produced antipolysaccharide antibodies were structurally different. Cross-reaction, even if greater than 90% by binding inhibition, appears to involve only part and not all of the variable regions.

Animals↗