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L Gebuhrer

Publications and source records attributed to L Gebuhrer.

At least 19 recordsLinked to original sources
PubMed2006

A deletion in exon 3 results in a new HLA-A*01 null allele (A*0115N) in a Martinican woman.

We report the identification of a new HLA-A null allele, HLA-A*0115N. This null allele has been identified within the A*01 group by a combination of serological and molecular typing [Polymerase chain reaction (PCR) sequence-specific primers, PCR sequence-specific oligoprobes and sequence-based typing (SBT)] in a potential intrafamilial bone marrow donor from Martinique (French West Indies). To characterize this A*01 null allele, we performed DNA typing by PCR-SBT on genomic DNA from the beginning of exon 2 (position 84) through the end of the exon 4 (position 895) and revealed a nucleotide deletion at the end of the exon 3. This sole difference between the new allele and the HLA-A*0101 generates a premature stop codon (TGA) in the beginning of exon 4. This deletion most likely explains the lack of cell surface expression of the encoded protein despite the presence of A*01 allele. The absence of correct expression of the antigen on the cell surface was confirmed by one-dimensional isoelectric focusing (1D-IEF). To date, this is the fourth null allele described within the A*01 group.

Alleles↗
PubMed2005

Outcome and long-term follow-up of alloreactive donor lymphocyte infusions given for relapse after myeloablative allogeneic hematopoietic stem cell transplantations (HSCT).

In order to study efficacy, toxicity and the long-term results of donor lymphocyte infusions (DLI), we retrospectively analyzed DLI given for relapse after conventional allogeneic hematopoietic stem cell transplantation (HSCT) in 30 patients with a median delay of 107.5 months after transplant and 58 months after DLI. After DLI, 15 patients established full donor chimerism, three patients developed grade III and one grade IV acute GVHD. A total of 15 patients achieved a disease response. Among the 14 patients with chronic myeloid leukemia (CML), 11 are alive at the last follow-up: five are in complete molecular response (CMR) and two in complete cytogenetic response (CCR) with no other intervention after DLI, three in CMR after imatinib mesylate given after DLI and one in complete hematological response after imatinib mesylate and reduced-intensity conditioning allogeneic SCT performed after DLI. At the time of the last follow-up, 19 (63%) patients died and 11 (37%) remain alive. The 3-year probability of survival for the entire population, CML patients and non-CML patients, was 60, 93, 62% after transplantation, and 48, 80 and 48% after DLI, respectively. A multivariate analysis demonstrated a significantly worse survival rate after transplantation for female recipients, advanced disease and acute leukemia before transplantation.

Adolescent↗
PubMed2004

A new HLA-B44 allele (B*44020102S) with a splicing mutation leading to a complete deletion of exon 5.

Using a combination of serology and polymerase chain reaction with sequence-specific primer (PCR-SSP), we have identified in a volunteer bone marrow donor a new HLA class I antigen within the B44 serotype. This human leukocyte antigen (HLA)-B44 variant was typed as 'blank' by microlymphocytotoxicity, whereas the B*44020101 allele was identified by PCR-SSP. A family study confirmed the Mendelian segregation of this blank antigen identified on one of the maternal haplotype transmitted to her child. The DNA sequence of B*44new, now referred to as B*44020102S, performed from the promoter region to the 3' untranslated region revealed a single nucleotide difference (A/G) compared to B*44020101 at the end of intron 4 in the acceptor-splicing site. This mutation leads to an incorrect splicing characterized by the deletion of exon 5 that encodes the transmembrane domain of the HLA antigen. Indeed, full-length complementary DNA sequencing revealed a complete absence of exon 5. Fluorescence-activated cell sorter analysis confirmed the absence of expression of HLA-B44 on the cell surface in the donor, compared to the HLA-B44 positive control. The isoelectric focusing analysis failed to reveal the presence of an HLA-B44 antigen in the donor, showing that no normal HLA-B*44020101 allele was synthesized. The new B*440201010102S allele is a soluble form of B44 without any detectable cell-surface expression. It can thus be considered as a soluble antigen, a form apparently inactive and unfit for antigen presentation.

3' Untranslated Regions↗
PubMed2004

Three new DRB alleles routinely identified by sequence-based typing: DRB1*010103, DRB1*0326 and DRB3*0219.

We describe here two additional DRB1 alleles found in two Caucasoid recipient candidates for organ transplant and a new DRB3 allele found in a Caucasoid unrelated bone marrow donor from the German file. HLA-DRB generic and allele typing were performed using commercial kits, subsequently exon 2 was sequenced. We found a DRB1*010101 with a silent mutation at codon 68 and a DRB1*0306 with a mutation at codon 38 (T-C) which causes an amino acid substitution from Val to Ala. DRB3*0219 differs from DRB3*020201 by two-point mutations at codons 60 and 74 (A/C and A/G, respectively). These mutations at positions 266 and 308 were responsible for two amino acid substitutions (Tyr to Ser and Gln to Arg).

Base Sequence↗
PubMed2004

HLA class-I and HLA class-II phenotypic, gene and haplotypic frequencies in Tunisians by using molecular typing data.

The aim of this study is to define a reliable reckoning of gene frequencies and six-locus haplotypic frequencies of HLA-A, HLA-B, HLA-C, HLA-DRB1, HLA-DQA1, HLA-DQB1 and HLA-DPB1 in the Tunisian population. One hundred unrelated random, healthy people originating from various parts of Tunisia were typed for the alleles of the loci mentioned above by using the molecular techniques polymerase chain reaction--hybridization with oligonucleotide probe (PCR-SSO) and sequence specific primers (SSP). The population studied appeared to be in Hardy-Weinberg equilibrium. Allelic frequency distributions were observed at each locus. The most frequent HLA-A alleles were HLA-A*02 (39%) HLA-A*0101 (25%), HLA-A*30 (21%) and HLA-A*2301 (18%). Moreover, HLA-3A*3601, HLA-1A*6601, HLA-1A*3402 and HLA-2A*8001 were found; however, no HLA-A*4301 was detected. For the HLA-B locus, the most common in descending order were HLA-B*44 (22%), HLA-B*5001 (19%), HLA-B*51 (16%) and HLA-B*18 (15%). Among the 28 alleles HLA-Cw detected, HLA-Cw*6 and HLA-Cw*7 were highly predominant with the frequencies of 33 and 30%, respectively. For the HLA class-II loci, HLA-DRB1*0701, HLA-DRB1*11, HLA-DRB1*13 and HLA-DRB1*03 were the most frequent DR alleles. For the HLA-DPB1, HLA-DPB1*0401, HLA-DPB1*0301 and HLA-DPB1*0201 were the most frequent DP alleles. Many haplotypes were in a strong positive-linkage disequilibrium. The most frequent haplotypes for HLA-A, HLA-B, HLA-C and HLA-DRDQ were HLA-A*3301, HLA-B*1402, HLA-Cw*0802, HLA-DRB1*0102, HLA-DQA1*0101 and HLA-DQB1*0501; HLA-A*2402, HLA-B*0801, HLA-Cw*0702, HLA-DRB1*0301, HLA-DQA1*0501 and HLA-DQB1*0201; HLA-A*2902, HLA-B*4403.1, HLA-Cw*1601, HLA-DRB1*0701, HLA-DQA1*0201 and HLA-DQB1*0202; HLA-A*3002, HLA-B*1801, HLA-Cw*0501, HLA-DRB1*0301, HLA-DQA1*0501 and HLA-DQB1*0201, with frequencies between 0.025 and 0.015. These data can be used as control data for HLA disease associations and paternity studies, but they are also important for the evaluation of the probability rate of success in determining the optimal matched donor in unrelated stem transplantation for Tunisian patients or patients of Tunisian origin.

Alleles↗
PubMed2004

HLA antibodies and neonatal alloimmune thrombocytopenia.

A female baby with a severe thrombocytopenia at 18 x 10(9)/l was born to a 29-year-old (gestation 2/partum 2) mother. Scattered petechiae were present on her legs, arms, chest and face, but there was no bleeding, infection, fever or hepatosplenomegaly. A platelet antibody screening immunocapture test was positive, which was performed on the mother's serum 3, 12 and 38 days after delivery, but no platelet-specific antibodies were found by the monoclonal-antibody-specific immobilization of platelet antigen assay. The baby's platelets and lymphocytes and the father's platelets reacted strongly with the HLA antibodies present in the mother's serum. The neonate was treated with intravenous human immunoglobulin (Tegeline), 1 g/kg per day) 1, 2 and 3 days after delivery. The platelet count rose from 18 x 10(9)/l on day 0 to 37 x 10(9)/l on day 3 and to 227 x 10(9)/l on day 12. No platelet transfusion was needed. Several factors which developed hereafter lead us to think that this neonatal alloimmune thrombocytopenia is due to the transplacental passage of maternal HLA antibodies to the baby.

Adult↗
PubMed2003

Outcome of 27 patients with Hurler's syndrome transplanted from either related or unrelated haematopoietic stem cell sources.

Over the last 15 years, we have performed a total of 30 haematopoietic stem cell transplants on 27 children suffering from Hurler's syndrome. These children were of median age 11 months at the time of diagnosis and 25 months at the time of transplantation. The phenotype was severe in 21 cases (78%). The donor was familial in 13 cases: nine genotypically identical, one phenotypically identical father and three HLA-mismatched donors. Unrelated donors were selected in 17 cases: four phenotypically identical and 13 with 1-4 HLA mismatches. The conditioning regimen generally consisted of busulphan 600 mg/m(2) plus cyclophosphamide (Endoxan) 260 mg/kg and cyclosporin with methotrexate for GvHD prophylaxis. Rabbit anti-thymocyte globulin (Thymoglobuline) was given for all unrelated or familial mismatched transplantations. The median nucleated cell dose infused was 6.00 x 10(8) TNC/kg. No bone marrow (apart from one) was T cell depleted. For first transplants, engraftment was observed in 23/27 patients (pts) (85%). Primary graft failure was observed in 4/27 patients (16%), two were retransplanted from an unrelated donor, one with success. Four patients have died. The primary cause of death was infection in three cases (TRM : 11%) and disease progression in one case, after primary graft failure. Of the 23 living patients, two have disease progression after graft failure and 21 (78%) have functional grafts with a favourable long-term outcome after a median follow-up of 4.7 years, having either full or mixed chimaerism. Among surviving patients with functional grafts, 13 (62%) were transplanted from unrelated donors of whom 10 (77 %) had HLA disparities. There was a remarkably low incidence of GvHD. In our experience, haematopoietic stem cell transplantation using an HLA-matched familial donor or an HLA-matched or -mismatched unrelated donor without T cell depletion or irradiation can achieve a favourable outcome in Hurler's syndrome, with improved cognitive function, but with a limited effect on the corneas and skeleton.

Adolescent↗
PubMed2003

Multiple sclerosis-associated retrovirus particles cause T lymphocyte-dependent death with brain hemorrhage in humanized SCID mice model.

A retroviral element (multiple sclerosis-associated retrovirus, MSRV) defining a family of genetically inherited endogenous retroviruses (human endogenous retrovirus type W, HERV-W) has been characterized in cell cultures from patients with multiple sclerosis. Recently, MSRV retroviral particles or the envelope recombinant protein were shown to display superantigen activity in vitro, but no animal model has yet been set up for studying the pathogenicity of this retrovirus. In the present study, the pathogenicity of different sources of MSRV retroviral particles has been evaluated in a hybrid animal model: severe combined immunodeficiency (SCID) mice grafted with human lymphocytes and injected intraperitoneally with MSRV virion or mock controls. MSRV-injected mice presented with acute neurological symptoms and died within 5 to 10 days post injection. Necropsy revealed disseminated and major brain hemorrhages, whereas control animals did not show abnormalities (P <.001). In ill animals, reverse transcriptase-polymerase chain reaction (RT-PCR) analyses showed circulating MSRV RNA in serum, whereas overexpression of proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma was evidenced in spleen RNA. Neuropathological examination confirmed that hemorrhages occurred prior to death in multifocal areas of brain parenchyma and meninges. Further series addressed the question of immune-mediated pathogenicity, by inoculating virion to SCID mice grafted with total and T lymphocyte-depleted cells in parallel: dramatic and statistically significant reduction in the number of affected mice was observed in T-depleted series (P <.001). This in vivo study suggests that MSRV retroviral particles from MS cultures have potent immunopathogenic properties mediated by T cells compatible with the previously reported superantigen activity in vitro, which appear to be mediated by an overexpression of proinflammatory cytokines.

Animals↗
PubMed2002

Cyclosporin A inhibits dendritic cell maturation promoted by TNF-alpha or LPS but not by double-stranded RNA or CD40L.

Here, we investigated the influence of cyclosporin A (CsA) on dendritic cell (DC) generation. With this aim, human DC were propagated from monocytes in serum-free medium with granulocyte macrophage-colony stimulating factor and interleukin-4. DC were then exposed to tumor necrosis factor alpha (TNF-alpha) for maturation. Our results show that CsA does not impair commitment of monocytes into DC, as assessed by loss of CD14 and increase of CD40 and CD1a. However, TNF-alpha-induced DC maturation was affected, as CsA-treated DC expressed lower levels of human leukocyte antigen and costimulatory molecules but sustained levels of CD1a, and less DC expressed DC-lysosomal-associated-membrane-protein (LAMP) and CD83. Accordingly, CsA inhibited the allostimulatory and accessory cell functions of DC. Surprisingly, when other maturation stimuli were used, we observed that CsA significantly inhibited maturation induced by lipopolysaccharides but not by polyribocytidylic acid or CD40 ligand, as assessed by DC phenotype and functions. Therefore, our results indicate that CsA may differentially affect DC maturation.

Antigen Presentation↗
PubMed2001

Multiple sclerosis retrovirus particles and recombinant envelope trigger an abnormal immune response in vitro, by inducing polyclonal Vbeta16 T-lymphocyte activation.

A retroviral element (MSRV) defining a family of genetically inherited endogenous retroviruses (HERV-W) has recently been characterized in cell cultures from patients with multiple sclerosis (MS). To address the possible relationship with MS, direct detection of circulating virion RNA was proposed but revealed technically difficult to perform in standardized conditions, in the face of multiple endogenous HERV-W copies. A parallel approach has evaluated MSRV potential pathogenicity in relation to characteristic features of multiple sclerosis, in particular, T-lymphocyte-mediated immunopathology. We report here that MSRV particles induce T-lymphocyte response with a bias in the Vbeta16 chain usage in surface receptor, whatever the HLA DR of the donor. A recombinant MSRV envelope-but not core-protein reproduced similar nonconventional activation. Molecular analysis of Vbeta CDR3 showed that Vbeta16 expansions are polyclonal. Our results thus provide evidence that MSRV envelope protein can trigger an abnormal immune response with similar characteristics to that of superantigens.

Antigens, Viral↗
PubMed2001

Generation of helper and cytotoxic CD4+T cell clones specific for the minor histocompatibility antigen H-Y, after in vitro priming of human T cells by HLA-identical monocyte-derived dendritic cells.

BACKGROUND: There is now convincing evidence that minor histocompatibility antigens (mHag) may play a significant role in the pathogenesis of graft-versus-host disease after HLA-identical bone marrow transplantation. Indeed, in this clinical situation, T cells specific for mHag have been isolated. Here, we addressed whether one can generate mHag-specific T cells in vitro, without any in vivo immunization, among healthy blood donors. METHODS: We used monocyte-derived dendritic cells (Mo-DCs) as antigen presenting cells to induce primary responses between healthy HLA-identical siblings, in mixed lymphocyte dendritic cell reactions (MLDCRs). RESULTS: We show that CD4+ T-cell clones, specific for the mHag H-Y, can be generated in vitro. These clones were derived from a gender-mismatched positive MLDCR pair of HLA-identical siblings and were restricted by the HLA DQB1*0502 molecule. In addition, these CD4+ T clones were also able to lyse allogeneic targets with the same pattern of restriction and specificity than helper function. Finally, acute myeloid leukemia (AML) blast cells were susceptible to lysis by these clones. CONCLUSIONS: Altogether, these results predict that Mo-DCs could help to generate class II-associated, mHag-specific, T-cell lines or clones in vitro, between healthy blood donors, without any need of transplantation-mediated immunization.

Acute Disease↗
PubMed2000

Distinct subsets of dendritic cells resembling dermal DCs can be generated in vitro from monocytes, in the presence of different serum supplements.

We recently demonstrated that dendritic cells (DCs) can be generated from monocytes in the presence of high concentrations of human serum (HS), provided the extra-cellular pH is maintained at plasma values. Because monocyte-derived DCs (Mo-DCs) can also be generated in the presence of fetal calf serum (FCS) or serum-free medium, we have investigated whether these different culture supplements influence DC generation. With this aim, purified monocytes were cultured with GM-CSF plus IL-4 for 6 days and were further exposed to TNF-alpha for 2 additional days, in the presence of HS, autologous plasma (AP), FCS, or X-VIVO 20, a serum-free medium. Our results show that good yields of functionally mature DCs can reproducibly be obtained in the presence of HS or AP, as assessed by CD83 and CD86 up-regulation, dextran-FITC uptake, allogeneic MLR assays and the induction of an autologous response. Interestingly, the effect of serum on DC generation was probably not only quantitative, but also qualitative, since (i) the majority of HS- or AP-cultured DCs expressed CD83 with very weak levels of CD1a, whereas CD83+ DCs cultured in FCS or X-VIVO were mostly CD1a++; (ii) HS- and AP-cultured DCs were much more granular and heterogeneous than FCS- or X-VIVO-cultured DCs, and (iii) the presence of Birbeck-like granules was preferentially observed in HS- or AP-cultured DCs, as assessed by electron microscopy. That these different cells resemble dermal DCs (DDCs) was further supported by the observations that most of the cells displayed intracytoplasmic FXIIIa in the absence of Lag antigen, and expressed E-cadherin at very low levels. Altogether, our results indicate that starting from the same monocytic population, different subsets of DCs can be generated, depending on the culture conditions. Thus, HS or AP favors the generation of fully mature DCs that resemble activated dermal DCs, whereas FCS, or X-VIVO preferentially leads to the generation of less mature CD1a++ dermal-like DCs.

Antigens, CD1↗
PubMed2000

Outcome of unrelated bone marrow donor searches in 174 children resulting in 45 patients transplanted in the HLA-matched and -mismatched situation.

The aim of the study was to evaluate the outcome of unrelated bone marrow donor (UBMD) searches initiated for 174 children between 1986 and 1997. Seven patients were registered twice so that a total of 181 UBMD searches took place. At the time of registration, patients suffered from hematological malignancies (n = 121), non-malignant hemopathies (n = 26) and inborn errors (n = 34). Forty-five of the patients (26%) were given transplants from unrelated donors of whom 26 (58%) were HLA-mismatched transplants. Our strategy accepted HLA mismatches at the time of donor selection, using Thymoglobuline as part of the conditioning regimen. Of the 45 patients given unrelated donor transplants, overall survival was 60% at 3 years and concerned 27 patients of whom 14 were from HLA-mismatched donors. Disease-free survival for hematological malignancies was 65% in HLA-matched transplants and 50% in HLA-mismatched transplants. For some patients (16%) urgency led us to use alternative options: non-identical related donor (n = 14), autograft (n = 10), related cord blood transplant (n = 4). For others, UBMD searches were stopped because of favorable evolution (n = 29), death (n = 24), disease progression (n = 22) or other reasons (n = 21). By the end of the follow-up period, 88 patients had died (50%), 75 (43%) are currently alive with or without being transplanted of whom eight are still having active searches and 11 are no longer contactable. In conclusion, in severe disease in children, an immediate transplant from a partially matched donor might be preferable to a prolonged search for a full match. Consequently, this strategy increases the number of patients for whom a suitable donor can be found. We have chosen this option in order not to delay BMT; in so doing we have obtained encouraging results which include high overall survival, low incidence of acute GVHD grade III-IV and low percentage of relapse even in mismatched pairs.

Adolescent↗
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↗