Detection of antigen receptor gene rearrangements in lymphoproliferative malignancies by fluorescent polymerase chain reaction

Monoclonal rearrangements of antigen receptor genes in lymphoproliferative diseases are characterized by the specific sequence and the length of their junctional region, which can be used as markers of the proliferating clone. PCR techniques have greatly simplified routine detection of monoclonal rearrangements. But on the one hand, identification of the sequences requires sequencing methods and on the other hand, sizing of rearrangements by conventional analysis of PCR products on agarose or nondenaturing polyacrylamide gels may be uncertain. We have developed an approach based on amplification of rearranged IGH, TCRG and TCRD locus by fluorescent PCR associated to a computerized analysis of generated PCR products allowing their objective sizing. We tested this method on DNA samples from patients with acute lymphoblastic leukemia and chronic lymphocytic leukemia, whose pattern of IGH and TCRG rearrangements had been previously identified by Southern blot techniques. TCRG-PCR assay allowed detection of 100% of rearranged samples. No false-negative results were found but a high rate (60%) of Southern-negative and PCR-positive samples were identified. TCRD PCR-assay detected VD1-JD1 or VD2-D2/3 rearrangements in both acute lymphoblastic leukemia and chronic lymphocytic leukemia samples. IGH PCR assay permitted detection of all known rearranged samples. The sensitivity of these three different PCR assays (1% leukemic cells) was equivalent to that of other published PCR protocols. These results show the validity and reliability of the fluorescent PCR method for routine detection of IGH, TCRG and TCRD rearrangements. Sizing of PCR products by computerized analysis was also validated. It provides additional information on rearrangement patterns in lymphoproliferative diseases, as clonal rearrangements can be recognized by their size. This can be of great interest in various circumstances, particularly for detection and follow-up of oligoclonality.

Distribution of HLA-DRB1 alleles of patients with polymyalgia rheumatica and giant cell arteritis in a Mediterranean population

OBJECTIVE

To evaluate HLA-DRB1 associations in polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) compared to rheumatoid arthritis (RA).

METHODS

One hundred twenty-one patients were included and oligotyped: 79 with PMR alone and 42 with GCA (14 also had PMR). We also genotyped 1609 healthy controls and 433 patients with RA. Statistical analysis included Fisher's exact test and calculation of the odds ratio (95% CI).

RESULTS

Compared to controls, the DRB1*04 phenotype was increased in PMR (39.2%; OR = 2.4, p = 0.0005) and GCA (45.2%; OR = 3.1, p = 0.0005). This association was weaker than in RA (p = 0.01). DRB1*07 was more frequent in GCA (31.0%) than in PMR (13.4%; p = 0.03), but the difference was not significant in comparison to controls. The distribution of DRB1*04 subtypes was similar in PMR and GCA, but different from RA and controls. However, the frequency of 0402 and 0403 subtypes could not be distinguished from that in patients with RA. Double occurrence of RA associated alleles was less frequent in PMR and GCA (9.9%; p = 0.005) than in patients with RA (20.8%). There was no significant relationship between markers of disease activity/severity and HLA-DRB1 genes in PMR or GCA.

CONCLUSION

PMR and GCA were associated with HLA-DRB1*04, but more weakly than RA. Nevertheless, these data suggest that HLA-DRB1* genes are closely related to susceptibility in PMR, GCA, and RA and do not support the hypothesis of a different linkage to the 3rd hypervariable region of DRB1 alleles. By contrast with RA, HLA-DRB1* genes do not appear to be indicators of disease severity in PMR and GCA.

Autoantibodies predicting the outcome of rheumatoid arthritis: evaluation in two subsets of patients according to severity of radiographic damage

OBJECTIVE

Autoantibodies such as rheumatoid factor (RF), antikeratin antibodies (AKA), antiperinuclear factor (APF), and anti-RA 33 antibodies are considered of value for the diagnosis of RA. The purpose of this study was to evaluate these autoantibodies as predictors of severe radiographic damage in rheumatoid arthritis (RA).

PATIENTS AND METHODS

Eighty six patients with RA (70 women, 16 men) fulfilling 1987 ACR criteria were selected from a cohort of 469 patients followed up since the first year of RA onset because they could be divided in two groups according to the severity of the radiographic damage. These 86 patients had a mean (SD) disease duration of eight (four) years: 43 patients had severe radiographic damage (Larsen score > or = 2) and 43 had limited radiographic damage (Larsen score < 2). The two groups were matched by disease duration and sex. The following autoantibodies were looked for: RF, ANA, AKA, APF, and anti-RA 33 antibodies. In addition, HLA class II DR beta alleles and standard inflammatory parameters (erythrocyte sedimentation rate, C reactive protein) were determined.

RESULTS

Patients with severe radiographic damage differed from those with limited radiographic damage in that they had higher RF (p = 0.01), APF (p < 0.02), and AKA (p = 0.001) titres. Stepwise regression analysis was done to calculate the odds ratios (OR) for each clinical and laboratory variable; only presence of cutaneous nodules (OR: 14.9; 95% CI: 7, 128), HLA DRB1*04 or DRB1*01 (OR: 7.53; 95% CI: 1.32, 42.9), AKA (OR: 3.11; 95%, CI: 0.58, 16.8), a high erythrocyte sedimentation rate (OR: 2.66; 95% CI: 0.60, 11.9), and a high C reactive protein value (OR: 7.4; 95% CI: 1.43, 38.1) were predictive of severe radiographic damage.

CONCLUSION

These data suggest that the risk of severe radiographic damage in RA patients is higher when cutaneous nodules, HLA DRB1*04 or DRB1*01, and/or AKA are present. The other autoantibodies of diagnostic significance are of little help for predicting joint destruction.

Synergistic effect of two HLA heterodimers in the susceptibility to celiac disease in Tunisia

The DR and DQ HLA genotypes of 94 Tunisian children affected with celiac disease are analyzed so that we can gain a better understanding of the HLA component of this disease. All of them carry at least one of two specific heterodimers: a DQ heterodimer, encoded by DQA1*0501, DQB1*0201 and/or a DR heterodimer, encoded by the nonpolymorphic gene DRA and the DRB4 gene. Quantifying the relative penetrances of all susceptible genotypes gives evidence for a synergistic effect of these two heterodimers and for a dose effect of the alleles encoding the beta chains of these two heterodimers. The DR3DR7 individuals have the greatest risk. They present the two kinds of heterodimers and carry two DQB1*0201 alleles. Celiac disease is the first HLA-associated disease for which the at-risk genotypes are so well delineated.

Synergistic effect of two HLA heterodimers in the susceptibility to celiac disease in Tunisia

The DR and DQ HLA genotypes of 94 Tunisian children affected with celiac disease are analyzed so that we can gain a better understanding of the HLA component of this disease. All of them carry at least one of two specific heterodimers: a DQ heterodimer, encoded by DQA1*0501, DQB1*0201 and/or a DR heterodimer, encoded by the nonpolymorphic gene DRA and the DRB4 gene. Quantifying the relative penetrances of all susceptible genotypes gives evidence for a synergistic effect of these two heterodimers and for a dose effect of the alleles encoding the beta chains of these two heterodimers. The DR3DR7 individuals have the greatest risk. They present the two kinds of heterodimers and carry two DQB1*0201 alleles. Celiac disease is the first HLA-associated disease for which the at-risk genotypes are so well delineated.

Polymorphism of the HLA-DMA and DMB genes in rheumatoid arthritis

OBJECTIVE

To determine whether the HLA-DMA and DMB genes, whose encoded molecules are involved in HLA class II-restricted antigen presentation, contribute to the genetic susceptibility to rheumatoid arthritis (RA).

METHODS

One hundred ninety-one RA patients, 147 control subjects, and 218 HLA-DRB1 genotype-matched control subjects were oligotyped for DMA and DMB genes.

RESULTS

DMA*0103 and DMB*0104 were significantly increased in the RA patients compared with the randomly selected and the matched controls, thus indicating a direct influence of the DM genes. After stratification of the patients and matched controls according to DRB1 genotypes, only DMA*0103 was increased in the RA patients with DRB1*01, as well as in the patients negative for the RA-susceptibility DR alleles.

CONCLUSION

Our results suggest that DMA*0103 could play an additional role in the genetic susceptibility to RA.

Qualitative and quantitative analysis of HLA-DRB gene expression

Determination of the molecular mechanisms influencing HLA-DRB gene expression would allow better understanding of the regulation of the immune response in normal as well as in pathological conditions. We started an extensive sequencing analysis of the proximal promoter regions of the DRB genes and observed a nucleotide polymorphism involving the classical regulatory regions of the DRB promoters. These nucleotide substitutions were observed to induce variations of the promoter activities as assessed by chloramphenicol acetyl transferase assays and the quantification of DRB transcripts. Similar analysis performed in patients with rheumatoid arthritis strongly suggests dysregulation of HLA-DRB gene expression.

Quantitative analysis of the expression of the HLA-DRB genes at the transcriptional level by competitive polymerase chain reaction

In addition to polymorphism of the peptide-binding site, the density of the MHC class II molecules expressed on the membrane of APC could well play a significant role in the MHC-peptide-TCR interaction during the immune response. We therefore investigated the regulation of the expression of the HLA-DRB genes at the transcriptional level. A competitive PCR approach was used to estimate the quantities of the HLA-DRB transcripts in peripheral blood B cells. When comparing the amounts of steady-state mRNAs among the different DRB1 alleles, the DRB1 transcripts in the DR52 haplotype group were found to be 2.5 to 3.5 times more abundant than the DRB1*01 transcripts, 1.5 to 2 times more abundant than the DRB1*04 transcripts, and 7 times more abundant than the DRB1*08 transcripts. Within the DR52 haplotype group, the DRB1 and DRB3 transcripts had the same abundance. Taken together, these results are in good agreement with the previously reported transcriptional activities of the DRB promoters except for DRB1*04, thus suggesting a differential post-transcriptional regulation among the DRB1 mRNAs.

Quantitative analysis of the expression of the HLA-DRB genes at the transcriptional level by competitive polymerase chain reaction

In addition to polymorphism of the peptide-binding site, the density of the MHC class II molecules expressed on the membrane of APC could well play a significant role in the MHC-peptide-TCR interaction during the immune response. We therefore investigated the regulation of the expression of the HLA-DRB genes at the transcriptional level. A competitive PCR approach was used to estimate the quantities of the HLA-DRB transcripts in peripheral blood B cells. When comparing the amounts of steady-state mRNAs among the different DRB1 alleles, the DRB1 transcripts in the DR52 haplotype group were found to be 2.5 to 3.5 times more abundant than the DRB1*01 transcripts, 1.5 to 2 times more abundant than the DRB1*04 transcripts, and 7 times more abundant than the DRB1*08 transcripts. Within the DR52 haplotype group, the DRB1 and DRB3 transcripts had the same abundance. Taken together, these results are in good agreement with the previously reported transcriptional activities of the DRB promoters except for DRB1*04, thus suggesting a differential post-transcriptional regulation among the DRB1 mRNAs.

Sequenase sequence profiles used for HLA-DPB1 sequencing-based typing

Sequencing-based HLA typing (SBT) is a PCR based high resolution HLA typing method in which polymorphic regions of the gene are sequenced and directly used for typing. Currently, for class II SBT, alleles are identified by comparison of the exon 2 sequence with their corresponding allele sequence library. Routine SBT requires reliable identification of heterozygosity, and automated assignment of the alleles. In sequencing strategies different enzymes can be used for primer extension. The most characteristic difference between sequences obtained by two protocols using Sequenaseregistered, or Taq-cycle sequencing, respectively, is a difference in incorporation of nucleotides in the primer extension leading to different sequence profiles. In Taq-cycling sequencing variable nucleotide incorporation results in irregular, but reproducible peak patterns, whereas Sequenase incorporates nucleotides in nearly equal amounts, resulting in more even peak patterns. In a previously published multi-center study we evaluated HLA-DPB1 SBT using Taq-cycle sequencing, and showed that typing can reliably be performed, considering the specific sequence profiles. In this study the applicability of Sequenase for HLA-DPB1 SBT was tested. A panel of samples were typed by SBT at five test sites which participate in the Sequencing Based Typing component of the 12th International Histocompatibility Workshop. The panel represents the existing polymorphism at all known polymorphic positions of exon 2, both in homozygous and heterozygous combinations. The assignment of homozygosity and heterozygosity was validated by Multi-Sequence Analysis, performing cluster analysis of chromatographic data of all sequences at each position. Sequence characteristics were examined and considered for appropriate assignment. Data reveals that Sequenase sequencing can also reliably be used for HLA-DPB1 typing.

An evaluation of a multicenter study on HLA-DPB1 typing using solid-phase Taq-cycle sequencing chemistry

In HLA Class II genes, polymorphism is mainly located in the second exon. Most DNA based typing methods are confined to the identification of specific sequence motifs in the second exon. In contrast, Sequencing Based Typing (SBT) elucidates the entire exon 2 sequence for typing. Comparison of the obtained exon 2 sequence with an allele sequence library results in allele assignment. We tested the applicability of SBT using a protocol for amplification followed by solid phase Taq-cycle sequencing for HLA-DPB1 typing. A panel of 32 samples were typed by SBT at five test sites which are participating in the Sequencing Based Typing component of the 12th International Histocompatibility Workshop. The panel represents the existing polymorphism at all known polymorphic positions of exon 2, both in homozygous and heterozygous combinations. In this multicenter study we focused on the reliability of analyzing heterozygous sequences for HLA typing. A multi-sequence analysis approach, Polall, was developed to evaluate sequences obtained. The assignment of homozygosity and heterozygosity was validated by cluster analysis of chromatographic data of all sequences. Sequence characteristics were examined and considered for appropriate assignment. Differences in sequence characteristics that occurred between the test sites are considered in detail. The evaluation of data of 5 test sites reveals that Taq-cycle sequencing can reliably be performed for HLA-DPB1 SBT.

Prognostic factors in rheumatoid arthritis. Comparative study of two subsets of patients according to severity of articular damage

Clinical and biological profiles at the onset of the disease, obtained retrospectively, and human leucocyte antigen typing were studied in 47 rheumatoid arthritis (RA) patients with severe articular damage (group 1) and in 47 patients with limited radiological abnormalities (group 2). The two groups were matched according to disease duration (mean: 8.1 yr). Systemic manifestations were more frequent in group 1. Erythrocyte sedimentation rate (ESR), platelet counts, C-reactive protein (CRP), rheumatoid factor and IgG titres were higher and haemoglobin level lower in group 1. HLA class II genotyping demonstrated that 95.7% of patients in group 1 were Dw4, Dw14 or DR1 as compared to 55.3% in group 2 and 37.1% in normal controls. Two RA-linked DRB1 genes were detected in 34.1% of patients in group 1, vs 8.5% in group 2 and 7.9% in controls. Multiple logistic regression analysis demonstrated that ESR, CRP and genetic markers were the most relevant independent variables and when combined could indicate the outcome in early RA. These data confirmed that different RA subtypes with different prognoses could be associated with particular clinical, biological and genetic profiles. Moreover, some of these factors could serve as predictive markers for outcome at the onset of RA.

[Can the prognosis of early rheumatoid arthritis be predicted?]

Rheumatoid arthritis is a frequently and potentially severe disease which causes a functional handicap in nearly half the patients 10 years after the identification of the first clinical manifestations. Some patients develop very severe forms with joint destruction and multiple organ involvement while in others the disease remains benign, even after a long clinical course of several years. Theoretically, the future intensity of rheumatoid arthritis in a given patient cannot be predicted at the time of early diagnosis. No prognosis factor has been identified and universally accepted and validated. A marker of prognosis would be highly appreciated by clinicians who could then more closely adapt their management decisions to the disease potential. Clinical and biological data collected to date have provided a limited amount of prognostic information but recent progress in molecular biology suggests that genetic markers could be correlated with disease severity. Several HLA-DRB1 alleles including DR1*0401, DRB1*0404, DRB1*0101 and sometimes DRB1/1001 and DRB1/1402 are potential markers. In France 85% of the patients with rheumatoid arthritis have one of these genes compared with 25% in the general population. In patients with a "high risk" alleles, the second haplotype could also have prognostic value. It would appear possible to distinguish immunogenetically homogeneous subpopulations corresponding to the more severe forms of the disease. It is still too early to propose therapeutic strategies based on current prognosis markers, but a combination of the most pertinent markers should be already used to select homogeneous subsets of patients in fundamental research and clinical trials.

Immunogenetic study of couples with recurrent spontaneous abortions

OBJECTIVES

Clinical observations suggest that genetic and immunologic disparity could be a factor in fecundity. The HLA system (HLA) is polymorphic and TLX (Trophoblast Lymphocyte Cross-Reactive), which is also polymorphic, seems to be linked to it. The immunologic hypothesis follows that excessive HLA and TLX-sharing could explain the rejection of a semi-allogenic blastocyst. Study objectives are therefore twofold; To determine whether or not there is significant HLA-sharing between spouses with unexplained recurrent spontaneous abortions (RSA) and to determine whether or not there is an association between some HLA specificities and RSA.

STUDY DESIGN

The study includes only Caucasian couples that have had three successive spontaneous abortions. These were distributed in two groups: Group E: 18 couples either with known aetiology or with secondary RSA; Group U: seven couples with unexplained primary RSA; Control group C: 21 couples with at least two children and no spontaneous abortions. Tissue typing for HLA-A and B molecules was performed using serotyping methodology based on lymphocytotoxicity reaction. The different DRB1 alleles (class II) were determined by oligotyping with a non-radioactive reverse dot-blot methodology.

RESULTS

Statistical comparison shows that the number of couples without shared specificity is not significantly different between the three groups for each locus independently and for the set of three. Our results show also that the allelic frequencies are not significantly different between the three groups.

CONCLUSIONS

There is no higher HLA-sharing in couples with RSA than in fertile couples. Similarly, no particular HLA specificity can be associated with the RSA.

Lethal acute graft-versus-host disease in a liver transplant recipient: relations with cell migration and chimerism

We report herein the case of a patient who developed fatal acute graft-versus host disease (GvHD) after liver transplantation (LT). GvHD occurred 18 days after LT and was characterized by skin epidermolysis, diarrhea and leucopenia. Skin biopsy showed epidermal dyskeratosis with epithelial necrosis, a lesion consistent with GvHD. Despite immunosuppressive therapy, the patient died within 24 days. In our observation, GvHD occurred although five HLA compatibilities were identified between the donor and the recipient, an apparently favorable and uncommon situation. This case further supports the qualification that LT may be complicated by GvHD and strongly suggests that minor rather than major histocompatibility antigens are the main target of allogenic interactions of GvHD. The involvement of chimerism in GvHD is controversial and requires further investigation.

Differential transcriptional activities of HLA-DR genes in the various haplotypes

The regulation of HLA class II genes is of particular interest with regard to the modulation of the immune response. The polymorphism of their coding regions is directly involved in the specificity of the Ag presentation, and their level of expression affects the extent of T cell activation. Previously, we have described an allelic polymorphism in the proximal promoter regions of HLA-DRB genes. The aim of this study was to compare the transcriptional activities of the promoters of the DRB genes and DRB1 alleles in a transient expression system. We have demonstrated a marked difference in their promoter strengths, as determined by their relative abilities to initiate transcription of the chloramphenicol acetyltransferase reporter gene in human B cell lines. The polymorphism of the promoter regions has been mapped to the regulatory boxes, and, by using gel retardation experiments, we found a differential ability of the nuclear proteins to bind to the partially conserved X box regions. Taken together, our results demonstrate the functional consequences of the allelic polymorphism of the proximal promoter regions of the DRB genes. These findings strongly suggest the existence, for the HLA-DR genes, of an interdependence between the polymorphism of the coding regions, which directly affects the capacity of peptide binding, and the polymorphism of the regulatory regions, which influences the transcriptional activities of the promoters.

Differential transcriptional activities of HLA-DR genes in the various haplotypes

The regulation of HLA class II genes is of particular interest with regard to the modulation of the immune response. The polymorphism of their coding regions is directly involved in the specificity of the Ag presentation, and their level of expression affects the extent of T cell activation. Previously, we have described an allelic polymorphism in the proximal promoter regions of HLA-DRB genes. The aim of this study was to compare the transcriptional activities of the promoters of the DRB genes and DRB1 alleles in a transient expression system. We have demonstrated a marked difference in their promoter strengths, as determined by their relative abilities to initiate transcription of the chloramphenicol acetyltransferase reporter gene in human B cell lines. The polymorphism of the promoter regions has been mapped to the regulatory boxes, and, by using gel retardation experiments, we found a differential ability of the nuclear proteins to bind to the partially conserved X box regions. Taken together, our results demonstrate the functional consequences of the allelic polymorphism of the proximal promoter regions of the DRB genes. These findings strongly suggest the existence, for the HLA-DR genes, of an interdependence between the polymorphism of the coding regions, which directly affects the capacity of peptide binding, and the polymorphism of the regulatory regions, which influences the transcriptional activities of the promoters.

Family studies in narcolepsy

Out of a population of 188 unrelated narcoleptic probands, we identified 14 probands (7.44%) with a family history of narcolepsy, 23 (12.23%) with a family history of isolated repeated episodes of naps and/or lapses into sleep and 151 (80.31%) without a family history of either condition. Clinical, polysomnographic or zygotic differences could not be evidenced in the three groups. Empirical risk for narcolepsy was 40.7 times greater among first-degree relatives of narcoleptics than in the general population. Narcolepsy and the condition characterized by isolated repeated episodes of naps and/or lapses into sleep have a common genetic component. This finding has important implications. Indeed, when the latter condition is included in the spectrum of narcolepsy, the empirical risk figure is relatively close to that expected in cases of simple mode of inheritance. A trend in favor of a more frequent transmission through mothers than fathers is emphasized.

High risk genotypes for celiac disease

It is known that celiac disease is strongly associated with an HLA class II component and that most patients carry the dimer DQA1*0501, DQB1*0201. We show in this study that the risk for a carrier of this heterodimer is independent from the number of possible heterodimers, from whether DQA1*0501 and DQB1*0201 are in cis or trans position and from the number of DQA1*0501 (one or two) but strongly depends on the number of DQB1*0201. In the Tunisian population we studied, the risk of developing celiac disease is estimated to be 6.8 times greater for those having a double dose of DQB1*0201 than for other dimer carriers. We replicated this result in published data of four other populations (Italy, Czekoslovakia, United Kingdom, Norway).

Differential expression of HLA-DRB genes according to the polymorphism of their regulatory region

The polymorphism of the HLA-class II molecules is directly involved in the specificity of the antigen presentation. We have previously described an allelic polymorphism in the proximal promoter region of the HLA-DRB genes. In this study, we demonstrate that this polymorphism has functional consequences on the transcriptional activity of the promoter of the different DRB genes. Indeed, transiently transfected DRB gene promoters into human B cell lines showed a marked difference in their ability to induce transcription of the chloramphenicol acetyl transferase (CAT) reporter gene. These findings suggest the presence of two interdependent effects of the HLA-class II molecules on the specificity of the immune response: one corresponding to the allelic polymorphism of the peptide-binding site and the second resulting from the polymorphism of the promoter regions inducing a variable expression of the DRB genes.

Investigation of the HLA component involved in rheumatoid arthritis (RA) by using the marker association-segregation chi-square (MASC) method: rejection of the unifying-shared-epitope hypothesis

In order to investigate the HLA component involved in rheumatoid arthritis (RA), we tested genetic models by the marker association-segregation chi 2 (MASC) method, using the HLA genotypic distribution observed in a sample of 97 RA patients. First we tested models assuming the involvement of a susceptibility gene linked to the DR locus. We showed that the present data are compatible with a simple model assuming the effect of a recessive allele of a biallelic locus linked to the DR locus and without any assumption of synergistic effect. Then we considered models assuming the direct involvement of the DR allele products, and we tested the unifying-shared-epitope hypothesis, which has been proposed. Under this hypothesis the DR alleles are assumed to be directly involved in the susceptibility to the disease because of the presence of similar or identical amino acid sequences in position 70-74 of the third hypervariable region of the DRBI molecules, shared by the RA-associated DR alleles DR4Dw4, DR4Dw14, and DR1. This hypothesis was strongly rejected with the present data. In the case of the direct involvement of the DR alleles, hypotheses more complex than the unifying-shared-epitope hypothesis would have to be considered.

Polymorphism in the regulatory region of HLA-DRB genes correlating with haplotype evolution

Class II genes of the human major histocompatibility complex (MHC) are polymorphic. Allelic variation of the coding region of these genes is involved in the antigen presentation and is associated with susceptibility to certain autoimmune diseases. The DR region is unique among human class II regions in that multiple DRB genes are expressed. Differential expression of the different DRB loci has been demonstrated, and we sequenced the proximal promoter region of the HLA-DRB genes, known to be involved in the regulation of these genes. We found locus-specific and allele-specific nucleotide variations in their regulatory regions and we determined the relationship between the regulatory regions of HLA-DRB genes. This polymorphism found in the regulatory conserved boxes could be involved in the observed differential expression of DRB loci. In addition, we found a polymorphism between the regulatory regions of DRB1 alleles which might be involved in an allele-specific regulation and therefore could be considered as an additional factor in susceptibility to autoimmune diseases.

Autoimmune hypothesis in narcolepsy

Since the discovery of an almost 100% association of HLA-DR2 with narcolepsy-cataplexy, many efforts have been made to demonstrate the intervention of immune factors in the pathogeny of the disease. Some epidemiological features could support this hypothesis: age of onset around 25, triggering factors, association with multiple sclerosis. Molecular studies at the DNA level have, up to now, failed to uncover an abnormal gene in the HLA system, which would imply that the DR2 antigen acts through its role in the immune response. However, results have been largely inconclusive as far as classical features of autoimmunity in blood and CSF are concerned. In canine narcolepsy, a linkage with a human immunoglobulin-related gene has recently been shown, and may constitute a counterpart of the HLA association in man. Thus, the hypothesis of a transient and discrete autoimmune aggression may be ruled out.

Generic HLA-DRB1 gene oligotyping by a nonradioactive reverse dot-blot methodology

HLA-DRB1 allelic specificities can be determined using SSOs annealing to their complementary PCR-amplified target DNA. To perform HLA-DR oligotyping routinely for donors and recipients of bone marrow transplantation, a "reverse" dot-blot technique has been developed that consists in the hybridization of labeled PCR-amplified target DNA to SSOs that have been first attached to nitrocellulose membranes. The 15 oligonucleotides chosen enabled the following HLA-DRB1 "generic" specificities to be defined: DR1, BON, 2, 3, 4, 11, 11 JVM, 12, 13, 13 HAG, 14, 7, 8, 9, 10. The genomic DNA was amplified by asymetric PCR with incorporation of biotinylated deoxynucleotides predominantly to generate labeled single-stranded DNA. Hybridization between specific immobilized oligoprobes and target DNA was nonradioactively detected by a colorimetric reaction using alkaline phosphatase. The reverse dot-blot methodology was successfully tested, first, for the determination of HLA-DR4 subspecificities, and then the procedure was routinely applied to the generic HLA-DR oligotyping of bone-marrow donors and recipients.