J. Hundrieser

Patterns of donor-type microchimerism after heart transplantation

Allogeneic microchimerism of donor-type has been demonstrated in stable patients in the long-term after organ transplantation. We have analysed microchimerism in skin and blood of 47 heart-transplanted patients after transplantation with polymerase-chain-reaction amplification specific for donor HLA-DRB1. Microchimerism was detectable in 50% of the patients in the first 6 months, in 100% between 6 months and 2 years, and in 58% in the third postoperative year or later. The state of chimerism was not related to acute or chronic rejections. Patterns of microchimerism after heart transplantation may be dynamic, but any association with clinical and immunological variables remains to be elucidated.

DNA Fingerprinting with the oligonucleotide probe (CAC)5/(GTG)5: somatic stability and germline mutations

SummaryDNA fingerprints were generated from various human somatic tissues and from peripheral blood of 179 children and their 80 parents using (CAC)5/(GTG)5 oligonucleotide probes. Whereas somatic stability of the fingerprint patterns was demonstrated, the average rate for germline mutations was estimated to be approximately 0.001 per DNA locus and gamete, with the three different restriction enzymes used. Seven out of eight mutations observed appeared to be of paternal origin.

Enhanced frequency of a PTPRC (CD45) exon A mutation (77C-->G) in systemic sclerosis.

A point mutation in exon A (C to G transversion at position 77) of human PTPRC (CD45) has recently been associated with the development of multiple sclerosis (MS) for at least a subgroup of patients. In the present report, we studied the frequency of the 77C→G transversion in two other autoimmune diseases namely systemic sclerosis (SSc) and systemic lupus erythematosus (SLE). The mutation was found with significantly enhanced frequency in patients suffering from SSc suggesting that PTPRC could play a role as susceptibility gene not only in MS but also in other autoimmune diseases. Further understanding of the mode of interaction of mutant PTPRC with other susceptibility genes may uncover mechanisms common in various autoimmune disorders.

The distribution of the Hb Constant Spring gene in Southeast Asian populations

SummaryThe distribution of the hemoglobin Constant Spring (Hb CS) gene in eight populations in Southeast Asia (including Assam) was determined using oligonucleotide hybridization. Hb CS was absent in two Assamese populations with a high prevalence of Hb E. The Hb CS gene frequency was 0.033 in northern Thailand and near 0.01 in central Thailand and Cambodia. High frequencies, between 0.05 and 0.06, were observed in northeastern Thailand. The present data and a similar study in Laotians suggest that the Lao-speaking populations of the Mekong River basin in northeastern Thailand and Laos have the highest frequencies of the Hb CS gene in Southeast Asia.

Selected di- and tetranucleotide microsatellites from chromosomes 7, 12, 14, and Y in various Eurasian populations

Microsatellite polymorphisms of nine Eurasian populations (>1200 chromosomes) were analyzed for the following loci: i) intronic (gt)n stretches of three T cell receptor (TCR) B loci on chromosome 7 (TCRBV6S1, TCRBV6S3, TCRBV6S7); ii) an intergenic (gt)n repeat in the region between the TCRDV3 and TCRAJ61 elements on chromosome 14; iii) two tetranucleotide simple repeats (D12S66, D12S67), not linked to known genes on chromosome 12; iv) a Y-chromosomal (gata)n polymorphism (DYS19). In general, allele frequencies and heterozygosity rates were similar, but specific alleles were missing in one or more populations. Distinct DYS19 alleles predominated in particular cohorts. Different allele frequencies were observed for the TCR loci in European and Asian populations. Tetranucleotide polymorphisms were distributed normally, whereas TCR alleles displayed bimodal frequency profiles. For TCRBV6S1 and TCRBV6S7, this profile reflects a diallelic protein polymorphism that correlates exactly with the length of the intronic repeats.

Genetic variation at twentythree microsatellite loci in sixteen human populations

We have analysed genetic variation at 23 microsatellite loci in a global sample of 16 ethnically and geographically diverse human populations. On the basis of their ancestral heritage and geographic locations, the studied populations can be divided into five major groups, viz. African, Caucasian, Asian Mongoloid, American Indian and Pacific Islander. With respect to the distribution of alleles at the 23 loci, large variability exists among the examined populations. However, with the exception of the American Indians and the Pacific Islanders, populations within a continental group show a greater degree of similarity. Phylogenetic analyses based on allele frequencies at the examined loci show that the first split of the present-day human populations had occurred between the Africans and all of the non-African populations, lending support to an African origin of modern human populations. Gene diversity analyses show that the coefficient of gene diversity estimated from the 23 loci is, in general, larger for populations that have remained isolated and probably of smaller effective sizes, such as the American Indians and the Pacific Islanders. These analyses also demonstrate that the component of total gene diversity, which is attributed to variation between groups of populations, is significantly larger than that among populations within each group. The empirical data presented in this work and their analyses reaffirm that evolutionary histories and the extent of genetic variation among human populations can be studied using microsatellite loci.

Development of microchimerism in pediatric patients after living-related liver transplantation

Microchimerism has been suggested to play an important role in the long-term acceptance of allogeneic organ grafts by transplant patients and for the maintenance of a state of donor-specific low responsiveness. In order to elucidate the kinetics of the development of chimerism we have performed a follow-up analysis in 10 pediatric patients with living-related liver transplantation (LRLTx). Blood samples obtained during the first 6 months and at 18 months post-transplant and skin biopsies taken at one month were analysed for the presence of donor cells by PCR using donor-specific HLA-DRB1 primer pairs or primers for a Y chromosome-specific sequence. Furthermore 13 long-term patients more than 2 yr after LRLTx were studied at two different time points. In the follow-up studies donor cells could be demonstrated in the blood of all patients immediately after transplantation. After a gradual decline all patients became chimerism-negative for several weeks or months. At 6 months, however, in five of eight patients tested and at 18 months in six of nine patients donor cells had reappeared. This biphasic pattern in the development of chimerism is proposed to reflect the occurrence of different donor-derived cell populations in the recipient. The population giving rise to the first wave of chimerism probably represents matured cells with a limited lifespan which are released from the graft into the circulation of the recipient during the first weeks after transplantation. The population of cells occurring with the second wave of chimerism is likely to have been generated by donor-derived cells with stem cell potential located either in the graft or in the hematopoetic organs of the recipient after emigration from the graft. This model may be able to explain fluctuations in the incidence and degree of microchimerism described in other patient populations during the first year post-transplant. Of the 13 long-term patients, chimerism could be demonstrated in 11. In seven patients it was detected in both blood and skin, in three patients the results obtained for blood and skin were discordant. In one patient only blood was analysed. It is not clear whether the negative results really reflected the absence of chimerism or whether the number of donor cells was below the level of detectability.

Linkage relationships and allelic associations of the cystic fibrosis locus and four marker loci

SummaryThe linkage relationships between the cystic fibrosis (CF) locus and four marker loci (MET-H, MET-D, D7S8 and D7S16), allelic associations between these loci and the extent of informativity at these marker loci were investigated in a sample of 206 families with at least one child affected by CF. The data were contributed by 11 laboratories from Europe and Israel. The maximum lod scores and recombination frequency estimates (

β-Globin gene linked DNA haplotypes and frameworks in three South-East Asian populations

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