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W van der Loo

Publications and source records attributed to W van der Loo.

At least 19 recordsLinked to original sources
PubMed1992

Patterns of interallelic divergence at the rabbit b-locus of the immunoglobulin light chain constant region are in agreement with population genetical evidence for overdominant selection.

Population studies at the b-locus of the "constant" regions of the rabbit immunoglobulin kappa 1 light chain (c kappa 1) revealed patterns of gene diversity resembling those that mark the peculiar nature of the major histocompatibility complex, such as large number of alleles, high heterozygosity levels, consistent excess of heterozygous individuals and long allele coalescence times. This paper documents the evolutionary patterns at the b-locus as inferred from DNA sequence comparisons. Among alleles, synonymous substitutions outnumbered expectations for neutral alleles by an order of magnitude. They were distributed randomly throughout the c kappa 1 coding region while interallelic amino acid differences did cluster into segments overlapping with the regions exposed to the solvent. Within these regions, acceptance rates of mutation at amino acid replacement sites were even higher than those at synonymous sites (dr/ds = 1.6-3.0), while in the intervals between these regions the opposite was found (dr/ds approximately 0.3). Under the assumption that allelic variation is adaptive at the molecular surface, the divergence patterns at the b-locus are therefore very similar to those reported for the major histocompatibility complex. An analysis at the quasi silent bas-locus (c kappa 2), which is linked to the b-locus, and comparisons among genes of the "variable" region of the kappa 1 light chains (v kappa 1), revealed patterns of divergence which differed markedly from those observed at the c kappa 1 constant regions. It is suggested that allelic variability at immunoglobulin constant regions can be due to mechanisms similar to those enhancing diversity at histocompatibility loci.

Alleles↗
PubMed1991

Estimation of gene diversity at the b locus of the constant region of the immunoglobulin light chain in natural populations of European rabbit (Oryctolagus cuniculus) in Portugal, Andalusia and on the Azorean Islands.

The minimal gene diversity at a locus of the antibody constant region, as estimated in natural populations of rabbit, revealed levels of heterozygosity similar to those reported for the major histocompatibility complex in human and murine populations. Sera of 416 wild rabbits were collected on the Iberian peninsula and on three islands of the Azorean archipelago and analyzed for the occurrence of the serological markers of the b locus of the immunoglobulin light chain. All four serotypes present in domestic rabbits were found in Portugal. They represented less than 50% of the gene pool. In Andalusia this was less than 15% and on the Azorean islands less than 10%. The pronounced and systematic hierarchy in allele frequencies, previously found in populations from the more recent distribution area of the species, was not observed. On the peninsula, the frequencies of the "domestic" alleles were similar, averaging 10%. The Portuguese sample revealed a total heterozygosity of at least 87%. This high value was supported by at least 11 serologically different alleles, none of them occurring at frequencies above 20%. These data are in agreement with an Iberian origin of the European rabbit and strongly suggest the coalescence of b locus allelic lines drawn from Iberian and western populations. The role of balancing selection in the evolution of the b locus polymorphism was further emphasized.

Alleles↗
PubMed1987

Nonrandom allele associations between unlinked protein loci: are the polymorphisms of the immunoglobulin constant regions adaptive?

Consistent linkage disequilibrium was observed between independently segregating protein loci. In natural populations of the European rabbit Oryctolagus cuniculus, highly significant, nonrandom associations between alleles of the constant regions of the immunoglobulin light and heavy chains were found, both within localities and between localities. We suggest that the population genetic data presented here are relevant to the adaptive significance of the genetic polymorphisms of the antibody constant regions.

Alleles↗
PubMed1979

Phylogeny of the rabbit gamma-chain determinants: a d12-like antigenic determinant in Pronolagus rupestris.

A survey for constant region gamma-chain allotypes (de locus) was undertaken in different lagomorph genera. As yet only Pronolagus rupestris, a paleolaginae, showed the presence of a determinant similar to rabbit d12 although it lacked the widespread e15 determinant. All seven individuals possessed the d12 like determinant which was studied by immunodiffusion, haemagglutination inhibition, radiobinding and binding inhibition assays. In addition, a new enzymic method for typing for d12, based on the presence of the asymmetric rabbit hinge carbohydrate linked to the d12 characteristic threonine, is presented. This method suggests, however, that, unlike the d12 rabbit, Pronolagus does not seem to have a majority of IgG molecules with a glycosylated hinge.

Animals↗
PubMed1979

Cell differentiation in the presence of cytochalasin B: studies on the "switch" to IgG secretion after polyclonal B cell activation.

Mouse spleen cells were cultured with lipopolysaccharide in conditions that activate both IgM and IgG secretion. Addition of cytochalasin B (CB), an inhibitor of cytokinesis, lead to a high degree of polynucleation, with little effect on Ig secretion. Using cytoplasmic staining with fluorochrome conjugated antisera, we determined the numbers of IgG-containing cells that also contained IgM in their cytoplasm. Such double staining cells were relatively more frequent at early times of the cultures, but at all times single producing cells were in the majority. Addition of CB over the period when the IgG producing cells first appear, lead to a marked increased frequency of double staining, polynucleated cells. This characteristic was stable over a period of at least 42 hr, suggesting that each double staining cell actively synthesized both isotypes. When CB was added after IgG production had started, little increase in the numbers of double staining cells were observed, although polynucleation remained extensive. These data confirm previous findings that the lineage of one cell can produce both IgM and IgG. Furthermore, the results suggest that cells in the process of switching from IgM to IgG go through an asymmetric division leading to one IgM-producing and one IgG-producing daughter cell.

Animals↗
PubMed1978

Expression of IgD by murine lymphocytes. Loss of surface IgD indicates maturation of memory B cells.

B lymphocytes capable of generating primary IgM and IgG plaque-forming cells (PFC) responses to burro erythrocytes have surface IgD, as do primary IgM PFC. IgG memroy cells arising after one injection of antigen are divided into two groups, one of which expresses surface IgD while the other has no detectable membrane IgD. PFC generated from the IgG memory cells lacking surface IgD show a higher average avidity than those arising from IgD-positive IgG memory cells, indicating that mature IgG memory cells do not have surface IgD. After more than one injection of antigen, few, if any, IgG memory cells have surface IgD. IgG PFC arising in primary or secondary immune response lack membrane-bound IgD. These data provide the outlines for a B-cell maturation pathway in which IgD marks unprimed and early memory B cells and is lost in mature memory cells. Studies presented here were conducted by isolating IgD+ and IgD- cells with the fluorescence-activated cell sorter and functional testing of the isolated populations in adoptive transfer experiments.

Animals↗
PubMed1977

Evidence for quasi-silent germline genes coding for phylogenetically ancient determinants of the rabbit a locus allotypes.

Anti-a2 sera raised in a3 rabbits are shown to detect determinants on a2 molecules which are different from those detected by anti-a2 sera raised in a1 animals. The former determinants are occasionally observed at a low level in rabbits of the a1 allotype and at a high level in sera of Leporidae of different genera. The two types of anti-a2 sera are shown to compete for the same sterical region of the a2 molecules. All homogeneous a2 molecules which have been tested show both types of determinants.

Amino Acid Sequence↗