Search PubMed⌕ Search

Biomedical subjects

M Abbal

Publications and source records attributed to M Abbal.

At least 19 recordsLinked to original sources
PubMed1992

[Study of CD45 isoforms on T CD8 lymphocytes, in the peripheral blood and the graft in patients after kidney transplantation].

We report characterization of CD45 isoforms expressed by CD8+ lymphocytes in peripheral blood and in the graft of 40 kidney transplanted patients who underwent kidney biopsy on the basis of clinical signs suggesting rejection. Standard histological examination of the biopsy fragments and three-color cytofluorimetric analysis of lymphocytes extracted from the same fragments by mechanical and enzymatic treatment were performed simultaneously and compared to the peripheral blood lymphocytes. In 14/40 biopsies where lymphocyte extraction succeeded, the predominant subset was CD8 (CD4/CD8 mean ratio was 0.53). Almost all CD8+ cells were activated: among these CD8+ cells, 55 percent were HLA-DR+, and 68 percent CD45RO+, i.e. of a memory cell type with cytotoxic activity. This situation resembles the in vitro observation made during mitogenic stimulation of lymphocytes by phytohemagglutinin, OKT3 or CML ("culture mixte lymphocytaire"). Beside their evident interest for the diagnosis, these data could be useful for our understanding of the physiopathology of the rejection crisis.

Biopsy, Needle↗
PubMed1992

Apparently non-expressed alleles of factor B (BF) code for hypomorphic proteins.

In three families with an apparent non-expressed factor B (BF) allele (BF*Q0), advanced methods of isoelectric focusing for the determination of BF F subtypes revealed different hypomorphic BF products (BF QL) with functional hemolytic activity expressed by the assumed BF*Q0 allele. A Taq I and a Msp I restriction fragment length polymorphism as well as the Ba fragment of the expression products showed banding patterns for the BF*QL alleles corresponding to BF S types, whereas an altered Bb fragment was seen in two BF QL products. In one family an intragenic recombination site within the Bb part of the BF gene was assumed. Investigations of factor B and its conversion fragments, as demonstrated by the used methods, allow to complement molecular genetic investigations of BF*Q0 alleles in heterozygous genotypes on a protein level. We conclude that apparently non-expressed alleles of factor B code for hypomorphic but functionally active proteins.

Alleles↗
PubMed1991

Computer-assisted kinetic assay for quantification of total complement activity.

Using apparatus available in any laboratory we developed a semiautomated kinetic technique for complement activity assay. Hemolysis of sensitized red blood cells is performed in the thermostated microflow cell of a spectrophotometer connected to a computer. The computer controls, displays on the screen, and analyzes all the different phases of the assay. After definition of optimal operating conditions, we compared the results obtained by this technique and by Kabat and Mayer's. On 221 patients' sera the regression coefficient was 0.94. The values for samples deficient in one fraction or after in vitro activation were very similar. The coefficient of variation was close to 1% for within series studies and better than 3% between series. This technique is very easy to perform even in a routine nonspecialized laboratory and up to 30-40 sample/h can be tested.

Antibodies↗
PubMed1991

[Immunogenetic markers (BF, C2, C4, 21-OH, TNF alpha, TCR beta, Ig) and insulin-dependent diabetes in the Tunisian population: serological and molecular study].

48 Tunisian people suffering from the IDDM auto-immune disease were compared to 35 control healthy persons for the polymorphisms of the complement BF, C2 and C4 proteins and genes, of the IgG (Gm allotypes) as well as of the TNF alpha and TCR C beta genes. Our study shows that the BFF1-C4A3-C4BQO and BFS-C4AQ0-C4B1 complotypes are associated to IDDM (RR of 2.97 and 3.07 respectively), as previously reported for other circummediterranean populations. The frequency of the Gm 21.28; 1.17; .. haplotype is increased, but not significantly, among the patients. The RFLP analysis reveals that the 2.65 kb SacI allelic restriction fragment of the C2 gene may be considered as a genetic marker of susceptibility to IDDM because its frequency raises to 0.206 among the patients vs 0.021 in the healthy individuals (p less than 0.001). The frequencies of the C4AQ0 and C4BQ0 alleles are more important among the IDDM patients than within the control sample, but the only C4BQ0 allele frequency is significantly increased. Both C4AQ0 and C4BQO result mainly from deletions. The frequencies of the allelic restriction fragments of the TNF alpha and TCRC beta genes are not significantly different among the patients and the controls. But the small sample size don't allow us to conclude definitively. It would be very interesting to extend the RFLP analysis to the TCR V beta and V alpha gene regions on more numerous samples.

Adolescent↗
PubMed1990

Defective, deleted or converted CYP21B gene and negative association with a rare restriction fragment length polymorphism allele of the factor B gene in congenital adrenal hyperplasia.

Defects in the enzyme, steroid 21-hydroxylase, result in congenital adrenal hyperplasia (CAH), a common autosomal recessive disorder of cortisol biosynthesis. The gene encoding this protein (CYP21B) and a closely linked pseudogene (CYP21A) have been mapped in the HLA complex on chromosome 6p, adjacent to the complement genes C4B and C4A, about 80 kb from the factor B gene. Molecular analyses of patients with CAH have shown that the cause of the defect may be either a deletion, a point mutation or a conversion of the active gene. Linkage of the disease to HLA has previously been studied by several groups. We have analyzed DNAs from patients with classical and non-classical CAH and from their family members, by probing with CYP21, C4 and BF cDNAs. In 70% of the CAH haplotypes studied, the defective CYP21B gene was indistinguishable from its structurally intact corresponding gene in Southern blot analysis, and presumably bore point mutations. In the remaining chromosomes, evidence for gene conversions, deletions and various deleterious mutations of the CYP21B gene is given. Moreover, our linkage studies show that a polymorphic TaqI cleavage site in the factor B gene, recently described by us, may be a new and useful genetic marker, because we found this TaqI restriction site only in unaffected haplotypes carrying functional CYP21B genes and, therefore, in negative association with the defective CYP21B gene.

Adrenal Hyperplasia, Congenital↗
PubMed1990

Molecular characterization of human complement factor B subtypes.

While several laboratories have agreed that there are two subtypes of the BF*F alleles, no information has been available until now at the molecular level. The region of the BF gene corresponding to the Ba fragment [1.7 kilobases (kb)] of the BF*S, BF*FA, and BF*FB alleles has been sequenced after specific amplification using the polymerase chain reaction (PCR). A point mutation at codon 7 has been revealed converting a cytosine in the BF*S allele to a thymidine in BF*FB. At the translational level an arginine residue in BF*S is substituted for a tryptophan residue in BF*FB. The amino-terminal sequencing of factor B immunoprecipitated from serum has been carried out from microquantities of protein blotted onto polyvinylidene fluoride (PVDF) membranes. We have shown that the difference between the BF*FA and the BF*FB subtypes in characterized by a glutamine at position 7 in BF*FA and a tryptophan in BF*FB.

Base Sequence↗
PubMed1990

Factor B reference typing report.

In a factor B (BF) Reference Typing of the VIth Complement Genetics Workshop and Conference, Mainz, FRG, 1989, 99 samples from 13 laboratories, including 18 families, were investigated with the majority of presently known typing procedures. Among the major ('standard') allotypes BF SO4 was found to be new. For the group of common BF F subtypes samples from 11 laboratories including complete family data from 5 laboratories were compared. The subtypes BF FA and FB were recognized and confirmed to be identical in the samples from all groups. Within a third group rare subtype variants of F and S were compared and characterized. In samples submitted from individuals with assumed non-expressed (BF*QO) alleles unexpected and hypomorphic gene products were seen. The investigation of DNA samples for restriction fragment length polymorphisms from the same set of individuals revealed a correlation of the Msp I 0.7-kb fragment with BF F, and confirmed the correlation of a Taq I 6.6-kb fragment with BF FA.

Alleles↗
PubMed1990

BF DNA reference typing.

A study of the RFLP patterns of the samples submitted, using TaqI and MspI restriction enzymes has allowed a confirmation of the correlation previously reported on the BF protein types and subtypes. The 6.6-kb band obtained with TaqI is closely correlated to the BF FA type and the MspI 0.7-kb band with BF F.

Blood Grouping and Crossmatching↗
PubMed1990

Factor B (BF) nomenclature statement.

A common nomenclature for factor B (BF) allotypes is recommended as a result of the BF Reference Typing of the VIth Complement Genetics Workshop and Conference, Mainz, FRG, 1989. It has generally been agreed that the alphanumeric BF nomenclature according to Mauff et al. should also be used in the future for all major BF allotypes distinguishable by standard agarose gel electrophoresis (AGE). The common BF F subtypes and further described rarer subtype variants are not detectable by standard AGE. Therefore, the nomenclature had to be extended. For the subtypes of BF F an alphabetical designation with capital letters will now be used: FA and FB. The designation of the five rarer subtype variants was modified after the reference typing to FB1, FB2, SB1, SB2, and SB3. Hyposynthetic variants detected in samples with previously assumed non-expressed (BF*Q0) alleles are now designated as SQL, M1QL, and M2QL, HQL' characterizing their lower concentration.

Complement Factor B↗
PubMed1988

Improvement of electrophoretic transfer by casting acrylamide gels on a cellophane sheet.

Electrophoretic transfer of protein after isolectric focusing using a polyacrylamide gel of less than 0.5 mm is difficult if the gel is backed to an electrically nonconductive casting support, such as glass plate or plastic films. By casting the gel on a cellophane sheet, it is not necessary to remove the gel from the support prior to electrophoretic transfer. The use of a cellophane support does not alter the quality of the final pattern.

Acrylamides↗
PubMed1988

The susceptibility to insulin-dependent diabetes mellitus is associated with C4 allotypes independently of the association with HLA-DQ alleles in HLA-DR3,4 heterozygotes.

In the genetically homogeneous Danish population, 27 HLA-DR3,4 heterozygous patients with insulin-dependent diabetes mellitus (IDDM) and 19 DR3,4 heterozygous controls without family history of IDDM were investigated for HLA-region markers and Gm and Km immunoglobulin allotypes. The aim was to define susceptibility factors for IDDM development other than HLA-DR using a number of techniques: lymphocytotoxicity (HLA-DR and DQ antigens), cellular methods (Dw and DP typing), restriction fragment length polymorphism (DQ alleles), electrophoresis and immunofixation (BF and C4 allotypes), and passive hemagglutination inhibition (Gm and Km immunoglobulin allotypes). The complement allotype C4A3 and the HLA-DQw8 (DQw3.2) antigen were found in all of the patients, whereas this was the case for only 8 of the 19 controls (P = 6 x 10(-6)): five lacked C4A3, five others lacked DQw8, and one of the controls lacked both of these factors. Fourteen of the patients had the complement allotype C4B3 versus three of the controls (P = 0.01). Previously reported family studies suggest that these alleles are part of the following haplotype: B15, BFS, C4A3, C4B3, DR4, Dw4, DQw8, and these factors were found together in ten of the patients versus one of the controls (P = 0.01). The markers usually associated with DR3 did not show significant differences between IDDM patients and controls, and the non-HLA markers studied showed no significant deviation from what was expected. In addition to the susceptibility factor DQw8, the study suggests the existence of susceptibility genes for IDDM near the complement C4 genes on DR4-carrying haplotypes.(ABSTRACT TRUNCATED AT 250 WORDS)

Complement C4↗
PubMed1988

Polymorphism of MHC class III genes: definition of restriction fragment linkage groups and evidence for frequent deletions and duplications.

The loci for the complement proteins BF and C2 and the two loci for C4 are closely linked to one another, as are the duplicated steroid 21 hydroxylase (21-OHase) genes to the C4A and C4B loci. The alleles of these four loci occur in specific combinations termed "complotypes". We have studied the gene frequencies of their different products in the Lebanese population and compared these values with those found in other populations. We observed a novel complotype (S B 4 6) in one family and a complotype with a so far undescribed variant of the C4A locus. Using several restriction fragment length polymorphisms (RFLPs), we have defined restriction fragment linkage groups. The combined use of C4 and 21-OHase probes allowed us to detect different types of deletions and duplications at these loci in the Lebanese population.

Chromosome Deletion↗
PubMed1988

C4A7: a new variant of human complement C4.

A rare variant of complement C4 was found in 2 related individuals. It has the most anodic mobility found to date, no hemolytic activity detected by the overlay technique and a Bgl II RFLP pattern very similar to that of the C4A6 type.

Alleles↗
PubMed1987

Human MHC class III genes, BF and C4. Polymorphism, complotypes and HLA class I and II associations in the Lombardy population (Italy).

The polymorphisms of the fourth component of human serum complement and factor B (BF) (controlled by class III MHC genes) was investigated in a panel of 250 unrelated individuals from the Lombardy population, previously HLA typed (A, B, C, DR, DQ antigens) and in 25 families. Nine different alleles at the C4A and eight at the C4B loci were detected. At both loci, alleles without a gene product (i.e. "null alleles") were observed with high frequency: 8.2% for C4A "nulL" and 10% C4B "null". As expected from allele frequencies the most common haplotype was C4A*3, C4B*1 (52%). The most common BF alleles, BF*S and BF*F had a frequency of 77.7% and 17.7% respectively, while the gene frequencies of SO.7 and F1 were 2.9 and 0.9% respectively. The association of complotypes and HLA haplotypes was analysed in 50 chromosomes. The most common combination, defined by class I, II and III alleles was B35-S31-DR5 (11%) followed by B16(38)-S31-DR5 with a frequency of 6.5%. Two duplications at the C4B locus were detected. A new variant (C4A*X) strikingly faster than that of the C4A*6 product was identified in two related individuals (aunt and nephew). The practical advantages of complotype determination in disease association studies and in healthy population is discussed.

Alleles↗
PubMed1986

A new HLA-D specificity associated with DR blank: D-BON.

Since 1980, a DR blank specificity undefined by serology but known to segregate in families linked to DQw1 has been recognized. We describe a Caucasoid family, BON... where 4 among 8 children are homozygous for such a specificity; their cells can be used as homozygous typing cells and the specificity defined is provisionally called D-BON. There is no known consanguinity in this family. The homozygous D-BON cells carry DR molecules as shown by their reactivity with monomorphic anti-DR monoclonal antibodies. In a random family material consisting of 210 haplotypes, the gene frequency of D-BON is between 1 and 2%, which corresponds to about 40% of the DR blank frequency. The D-BON specificity seems associated with DQw1 and also with B35 and C4B2.

Adult↗