PubMed Health⌕ Search

Biomedical subjects

L Gebuhrer

Publications and source records attributed to L Gebuhrer.

At least 19 recordsLinked to original sources
PubMed1998

Generation of stable monocyte-derived dendritic cells in the presence of high concentrations of homologous or autologous serum: influence of extra-cellular pH.

Recent studies have highlighted the high degree of differentiation of monocytes. Indeed, dendritic cells (DC) can be generated from monocytes, in the presence of appropriate cytokines. However, human serum is usually avoid in such cultures. Here, we report that human serum does not inhibit generation of mature DC from blood monocytes, but rather that extra-cellular pH may play an important role in the regulation of monocyte differentiation. Indeed, monocytes cultured at pH 7.4 in the presence of high concentrations of human serum developed efficiently into mature DC, as opposed with monocytes cultured at pH 7. These pH 7.4 cultured DC presented features characteristic of mature DC, at the phenotypical, functional and morphological levels. In addition, these DC were stable, with respect to their sustained expression of CD83 and CD86, upon withdrawal of cytokines. Finally, when autologous plasma was used instead of homologous serum, differentiation of monocytes into mature DC was efficient, as well. Thus, altogether, our data show the importance of extra-cellular pH on differentiation of monocyte-derived DC in the presence of human serum, which should be maintained at plasma levels.

Antigens, CD↗
PubMed1998

Sequence of four new HLA-Cw alleles: a possible role of interallelic recombination.

In order to extend our current understanding of HLA-C polymorphism, four new alleles have been cloned and sequenced: Cw*1801 in a donor of mixed origin, Cw*02024 in a Senegalese individual, Cw*1205 and Cw*1604 in European Caucasoid blood donors. HLA-Cw*1801, which most likely results from an interallelic recombination between Cw*0704 and 0401 alleles, was not associated with B*8101, but with either B*4403 or B18. The Cw*02024 allele differs from Cw*02022 by a silent mutation in exon 3. Both Cw*1801 and Cw*02024 appear to be rather frequent in populations of African origin but have not yet been detected in Caucasoids. HLA-Cw*1604 differs from Cw*1601 by two nucleotides at codon 156 leading to a Gln to Trp substitution. This new Cw16 subtype was subsequently identified in three additional unrelated families, all of South-European origin, and presented an unusual association with B*4402 in all cases. HLA-Cw*1205 is a composite allele with the alpha1 domain of Cw*1602 and the alpha2 domain of Cw*1203. It appears to be rare, at least in European Caucasoids. Three of these four alleles may have resulted from gene conversion-like or interallelic recombination events.

Alleles↗
PubMed1997

Correlation between clinical response to interleukin 2 and HLA phenotypes in patients with metastatic renal cell carcinoma.

HLA phenotypes were characterized for 79 patients with metastatic renal cell carcinoma treated with interleukin 2 (IL-2). HLA-A32 was associated with a clinical response (P = 0.025). The frequency of HLA-A3 and/or A32 was higher among responders than non-responders (P = 0.008). Thus, these results suggest that, in vivo, IL-2 may enhance cellular-mediated immunity against a tumour antigen and that some MHC molecules are more efficient than others for endogenous tumour antigen presentation.

Adult↗
PubMed1996

Sequence of a new HLA-DR4 allele with an unusual residue at position 88 that does not seem to affect T-cell allo recognition.

New HLA alleles can be identified by unorthodox patterns observed during low-resolution typing performed with sequence specific oligonucleotide probes (SSOP). One of the best examples is locus DRB1, where allelic subtypes are characterized by a combination of a limited number of residues located in three hypervariable regions of exon 2. HLA-DR oligotyping analysis of a female caucasoid bone marrow donor led to the identification of an individual that typed as DRB1*11, DRB3*02, DRB4*01, DQB1*0301-0302. This donor was, however, typed by serology as DR11 DR4, DR52, DR53, DQ7 DQ8. PCR-SSP typing for DR4 subtype revealed an amplification pattern typical for DRB1*0404. After sequencing the entire exon 2, a new DRB1 allele was identified: DRB1*04var that is identical to DRB1*0404, except for one nucleotide at codon 88 resulting in a Ser-->Arg exchange. This mutation had prevented amplification with the DR generic primers. Cellular typing by three HTCs-DRB1*0404/DW14 from the 9th Workshop showed that this DRB1*04var typed exactly like a DW14 cell. This suggests that residue 88 does not affect T cell recognition.

Alleles↗
PubMed1993

Implication of HLA-DR residues at positions 67, 71, and 86 in interaction between HLA-DR11 and peptide HA306-320.

To get further insight into the role of three polymorphic DR residues located in one alpha-helix of the HLA-DR binding groove, we studied how natural substitutions at positions 67, 71, and 86 on DR11 molecules influence MHC binding and/or T cell recognition of peptide HA306-320 and of monosubstituted peptide analogues. Our results show that: 1) Reactivities of all HA306-320-specific T cell clones tested are decreased by DR substitution at position 86 and can even be lowered by additional substitutions at position 71, and at positions 71 plus 67, indicating that these three residues are functionally important. 2) The functional effects of substitutions at positions 67, 71, and/or 86 cannot be explained by a decreased affinity of HA306-320 for the substituted DR11 molecules, as determined in binding assays. 3) More likely, they are explained by modifications of the conformation, orientation, or location of the peptide once bound in the HLA groove, because each individual DR substitution at positions 86, 71, and 67 differentially affects the binding ability of the same panel of 50 monosubstituted analogues. 4) This interpretation is reinforced by the identification of a small set of monosubstituted analogues that can compensate the functional effects of DR substitutions at positions 86, 86 plus 71, or 86 plus 71 plus 67, and thus restore T cell reactivities. All together these results strongly suggest that residues 67, 71, and 86 play a key role in interactions with HA306-320, probably by modifying the way the peptide is bound within the binding groove of HLA-DR11. Using the same DR11.1-restricted clones, we identified putative T cell and DR contact residues of HA306-320 by comparing DR binding and T cell-activating capacity of the peptide analogues. This analysis suggests that: 1) Residues 310, 311, 312, 313, and 316 are putative TCR contacts. 2) Peptide HA306-320 anchors to DR11.1 molecules mainly via residue Y-309, possibly at the vicinity of DR residue 86, whereas peptide residues 315 and 317 constitute minor aggregotopes that would be at the vicinity of DR residues 71 and/or 67. 3) Finally, residues 308, 310, and 314 might also be on the MHC side of the DR-peptide-TCR complex.

Amino Acid Sequence↗
PubMed1993

Restriction fragment length polymorphism of DQB and DRB class II genes of the ovine major histocompatibility complex.

The ovine major histocompatibility complex (MhcOvar) class II region was investigated by Southern blot hybridizations using ovine probes specific for the second exons of Ovar-DRB and Ovar-DQB genes. Multiple bands were revealed when genomic DNA was digested with each of five restriction enzymes (BamHI, EcoRI, HindIII, PvuII and TaqI), and successively hybridized with the two radiolabelled ovine probes. Restriction fragment length polymorphisms (RFLPs) were analysed in 89 sheep originating from six inbred families and the inheritance of the fragment patterns was determined. Forty-one fragments were recorded with the DQB probe; 32 were detected with the DRB probe. They constituted 9 DQB and 10 DRB allelic patterns. Twelve DQB-DRB haplotypes were resolved in this study.

Alleles↗
PubMed1993

Chimerism and tolerance to host and donor in severe combined immunodeficiencies transplanted with fetal liver stem cells.

We have studied the peripheral T cell repertoire of two patients with severe combined immunodeficiency who were successfully treated with human histocompatibility leukocyte antigen (HLA)-mismatched fetal liver stem cell transplantation. The patients presented a split chimerism. T cells were of donor origin, whereas the B cells/monocytes were of the host phenotype. Interestingly, the natural killer (NK) cells in one patient were donor derived and in the other patient of host origin. The NK cells were functional but did not have antihost or donor reactivity. Despite the HLA mismatch between donor and host cells, complete tolerance was achieved in vivo, and a specific unresponsiveness of peripheral blood mononuclear cells from both patients toward the host cells was demonstrated in vitro. Nevertheless, we could isolate T cell receptor (TCR)alpha beta, CD4+ or CD8+, T cell clones specifically reacting with HLA class I and II molecules of the host. The CD4+ host-reactive T cell clones from both patients produced interleukins 2 and 5, interferon-gamma, granulocyte/macrophage colony-stimulating factor but are specifically defective in interleukin 4 production. The frequencies of CD8+ host-reactive T cells were high, and were in the same range as those observed for CD8+ alloreactive T cells. In contrast, no donor-reactive CD8+ T cells or host or donor-reactive TCR gamma delta + T cells were detected. These data indicate that, after fetal stem cell transplantation, donor-reactive, but not host-reactive cells, are deleted from the T cell repertoire. Therefore, a peripheral mechanism of suppression or clonal anergy, rather than clonal deletion, is involved in maintaining in vivo tolerance toward the host.

Adolescent↗
PubMed1993

Fetal liver transplantation: biology and clinical results.

Over the last 18 years, we have developed the transplantation of fetal liver cells to treat severe immunodeficiencies, hematological disorders and inborn errors of metabolism. Post-natally, this treatment is successful in two-third of patients and it is therefore very valuable, especially when there is no perfectly matched donor for a bone marrow transplant. Since 1988 we have carried out these fetal liver transplants (FLTs) in utero, immediately after prenatal diagnosis. Engraftment and reconstitution have been obtained, and several advantages appear to be associated with in utero FLT: increased probability of graft take, ideal isolation of the patient (in the maternal uterus) and optimal environment for the differentiation of the transplanted fetal liver cells (in the fetal host).

Fetal Tissue Transplantation↗
PubMed1992

Apparent HLA DR triplet due to the coexpression of a DRB5-encoded molecule on a DR1 haplotype.

HLA DR1 molecules are coded by a single polymorphic DRB1 gene. We have observed rare DR1 cells in one Caucasoid family and three unrelated individuals that also reacted with some anti-DR2 sera. Since the second DR antigen was normally expressed, these cells appeared as triplets. Contrary to serology, the cells were not typed by HTCs defining Dw2, Dw12, and Dw21. Further investigations on these unusual DR1+2* haplotypes were conducted by DNA oligotyping and by sequencing of the DRB first-domain exon. The results showed that these DR1 haplotypes, besides their DRB1*0101 allele, carried also a DRB5*0101 allele.

Adult↗
PubMed1992

Alloantisera can detect some of the variants of HLA DRw13 identified by oligotyping.

Oligotyping has revealed a considerable polymorphism of HLA DRw13; so far, 5 alleles coded by DRB1 have been identified. An even greater number of haplotypes are apparent when considering the association of DRw13 with alleles coded by DRB3 and DQB1. Serology can now define some of these variants which had formerly escaped detection. We have tested by serology and by oligoprobes 66 genotyped Caucasoid cells comprising the known DR and DQ alleles. Among the 28 DRw6 cells, 10 different haplotype patterns were selected, of which 8 concern DRw13 and 2 DRw14. Four variants of DRw13 were represented: DRB1 *1301, *1302, *1303 and *1305 associated with usual and with uncommon alleles belonging to DRB3 and to DQB1. We have centered our analysis on 19 sera of the XIth Workshop defining DRw6. Two sera (639, 826) were noteworthy since they reacted with certain subtypes of DRw13 and with DRB1 *1102, *1103 only, the other DR specificities remaining negative.

Amino Acid Sequence↗
PubMed1992

In utero transplantation of stem cells in humans: immunological aspects and clinical follow-up of patients.

Four human fetuses were treated by transplantation of human fetal liver stem cells. Two of them had severe immunodeficiency disease and the two other ones had thalassemia major. Three of these in utero transplants were followed by engraftment. The three patients are now born: the first one is now very healthy thanks to the reconstitution of cell-mediated immunity associated with this transplant, and he lives normally at home; the two other ones, who have been more recently treated, have a significant improvement of their condition and they also live normally at home. This procedure, for the first time used in humans, has therefore demonstrated its feasibility and its efficacy: during early fetal development, foreign cells engraft readily and may result in cure or significant correction of a large variety of inherited diseases.

Blood Transfusion, Intrauterine↗