HLA-B27 typing by a group-specific PCR amplification

Combined use of different antibody clones improves the efficiency of human leukocyte antigen B27 detection by flow cytometry

BACKGROUND

Human leukocyte antigen B27 (HLA-B27) is an major histocompatibility complex Class I cell surface antigen that shows strong association with spondylarthropathies. Although polymerase chain reaction (PCR) is the gold standard method for HLA-B27 detection, monoclonal antibodies, and flow cytometric analysis is also frequently used. We aimed to compare the efficiency of two commercially available monoclonal antibody clones and the DuraClone kit that uses simultaneously these clones.

METHODS

Blood samples drawn from 63 patients were analyzed by flow cytometry and PCR. For flow cytometry analysis ABCm3 and FD705 clones were used for flow cytometry as well as the DuraClone Reagent Kit. Results of flow cytometric analysis were confirmed by PCR.

RESULTS

Numbers of false-positive and equivocal samples were high when ABCm3 or FD705 clones were used separately: 34 out of 63 and 27 out of 63, respectively. Simultaneous use of the two antibody clones and pre-selection of CD3+ T cells, in the DuraClone kit, significantly decreased the number of these samples. Using the DuraClone kit, only 11 out of 63 samples were inconclusive. Influence of HLA-B7 expression was detectable in some cases when ABCm3 and FD705 were used separately.

CONCLUSIONS

Our results show that simultaneous use of HLA-B27 monoclonal antibodies and pre-selection of T cells significantly increased the specificity of the flow cytometric assay, however it did not reach the specificity of PCR. Nevertheless, based on our results, performing the PCR test exclusively in equivocal cases by DuraClone kit reduces the burden of PCR assays and the turn-around time.

Real-time PCR based HLA-B*27 screening directly in whole blood

The linkage between the occurrence of human leucocyte antigen B*27 (HLA-B*27) and ankylosing spondylitis or other related spondyloarthritides is well documented. PCR based methods are widely used for HLA-B*27 screening. To refine HLA-B*27 testing we aimed at establishing a real-time PCR protocol to detect the HLA-B*27 allele directly in blood samples, without DNA extraction. HLA-B*27 analysis was performed by two real-time PCRs using TaqMan primer-probe assays for B*27 specific amplification of exon 2 or exon 3 of the HLA-B gene together with a mutant of Taq polymerase for direct blood PCR. Conditions for direct blood PCR were optimized and the reliability of the direct blood PCR protocol was evaluated by re-genotyping over 200 blood samples from patients who previously underwent routine DNA-based HLA-B*27 testing. Heating blood samples at 95°C for 10 minutes significantly improved PCR performance. Results from real-time PCR based HLA-B*27 testing directly in blood of over 200 patients were in 100% concordance with results obtained by routine DNA-based HLA-B*27 genotyping. In summary, we present a reliable real-time PCR protocol for HLA-B*27 screening directly in whole blood supporting fast clarification of the presence of ankylosing spondylitis or other spondyloarthritides in suspected cases.

Polymorphisms of human leukocyte antigen B*27 on clinical phenotype of spondyloarthritis in Chinese

BACKGROUND

In recent years, an ever-increasing number of alleles of human leukocyte antigen B*27 (HLA-B*27) have been identified. This study aimed to establish an updated method for HLA-B*27 subtyping, and to investigate the impact of HLA-B*27 polymorphisms on the clinical phenotype of spondyloarthritis (SpA).

METHODS

Overall, 184 SpA patients were recruited for analyzing diversity of HLA-B*27 via an updated high-resolution polymerase chain reaction amplification with sequence specific primers (PCR-SSP).

RESULTS

The prevalence of HLA-B*27 was 94.0%, and four subtypes were identified including HLA-B*2704 (77.5%), B*2705 (20.2%), B*2707 (1.7%), and B*2724 (0.6%). There was an obvious male predominance (P=.05) and markedly elevated C-reaction protein (CRP) in B*27 positive SpA (P<.01). In multivariate linear regression analysis, the elevated CRP was positively associated with HLA-B*27 positivity (regression coefficient B=46.1, P=.0003), grade of sacroiliitis (B=47.5, P=.0032), and male gender (B=20.4, P=.0041). Notably, a male predilection was also found in B*2705 positive SpA while B*2707 was associated with older age, higher positive family history, and higher prevalence of extra-articular features (all P<.05).

CONCLUSIONS

In this study, an updated PCR-SSP technique to identify increasing alleles of HLA-B*27 was developed and their different effects on clinical manifestations of SpA were demonstrated. Genotyping of HLA-B*27 would shed light on our understanding of the pathogenesis of SpA.

Rapid and reliable genotyping of HLA-B*58:01 in four Chinese populations using a single-tube duplex real-time PCR assay

AIM

HLA-B*58:01 is strongly associated with allopurinol-induced severe cutaneous adverse reactions. This study aimed to develop a new and convenient method for HLA-B*58:01 genotyping and to investigate HLA-B*58:01 distribution in different Chinese populations.

MATERIALS & METHODS

Combining of sequence-specific primers and TaqMan probe, a single-tube duplex real-time PCR assay for HLA-B*58:01 typing was established.

RESULTS

The HLA-B*58:01 genotyping result in Buyei (n = 100) by real-time PCR showed 100% concordance with those by sequence-based typing. The prevalence of HLA-B*58:01 carrier in Buyei (17%, n = 100) was significantly higher than those in Northern Han (4%, n = 100), Tibetan (5.1%, n = 99) and Uighur (2%, n = 50) populations (p < 0.05).

CONCLUSION

The newly developed reliable assay was appropriate for HLA-B*58:01 detection prior to allopurinol administration in clinical settings.

Application of a Simple In-House PCR-SSP Technique for HLA-B* 27 Typing in Spondyloarthritis Patients

Background. Microlymphocytotoxicity (MLCT) and flowcytometry (FC) are the conventional serological methods to detect HLA-B* 27. Due to some disadvantages in these methods, most of the HLA laboratories have now switched over to molecular methods. Molecular techniques based on commercial kits are expensive; as such many laboratories with limited funds in developing countries cannot afford these techniques. Aims. Our main aim was to standardize a simple inexpensive in-house PCR-SSP technique for HLA-B* 27 typing. Materials and Methods. Sequence Specific primers were designed to amplify all the subtypes of B* 27 using IMGT-HLA sequence database. Accuracy was checked by retyping of 90 PCR-SSOP typed controls. Results. The presence of 149 bp specific band with control band on 2% agarose gel showed B* 27 positivity. No discrepancies were found when compared with PCR-SSOP results. The frequency of HLA-B* 27 was found to be significantly increased (68.75% versus 4.40%, O.R 46.909: P value 6.62E − 32) among 700 SpA patients as compared to controls. Clinically, 54% of patients had polyarticular arthritis with SI joints involvement (68%) and restricted spine flexion (60%). Conclusion. In-house PCR-SSP technique is very simple and inexpensive technique to detect B* 27 allele, which was strongly associated with SpA patients from Western India.

Both baseline clinical factors and genetic polymorphisms influence the development of severe functional status in ankylosing spondylitis

Functional severity in ankylosing spondylitis (AS) patients is variable and difficult to predict early. The aim of our study was to assess whether a combination of baseline clinical factors and genetic markers may predict the development of severe functional status in AS. We performed a cross-sectional association study on AS patients included in the Spanish National Registry of Spondyloarthropathies—REGISPONSER. Bath Ankylosing Spondylitis Functional Index (BASFI) was standardized by adjusting for disease duration since the first symptoms (BASFI/t). We considered as severe functional status the values of BASFI/t in the top of the 60th (p60), 65th (p65), 70th (p70), and 75th (p75) percentile. We selected 384 single nucleotide polymorphisms (SNPs) distributed in 190 genes to be analyzed. The study cohort included 456 patients with mean age 50.8(±10.5) years and with mean disease duration since first symptoms 24.7 (±10.1) years. Older age at disease onset and neck pain at baseline showed statistical significant association with severe BASFI/t. Polymorphisms associated in the allele frequencies test with severe BASFI/t in all classifications were: rs2542151 (p60 [P = .04], p65 [P = .04], p70 [P = .001] and p75 [P = .001]) and rs2254441 (p60 [P = .004], p65 [P = .02], p70 [P = .01] and p75 [P<.001]).. Genotype association, after adjustment for covariates, found an association in three of the four patients' classifications for rs2542151 and in two of the classifications for rs2254441.Forward logistic regression did not identify any model with a good predictive power for severe functional development.

In our study we identified clinical factors and 24 polymorphisms associated with development of severe functional status in AS patients. Validation of these results in other cohorts is required.

Methods for diagnostic HLA typing in disease association and drug hypersensitivity

This chapter describes the application of diagnostic HLA typing for disease association and five methods used for specific HLA genotypes. The methods utilise a combination of polymerase chain reaction (PCR) amplification to detect sequence polymorphism by the presence or absence of amplification, nucleotide sequencing of the PCR product, and hybridisation of the PCR product with labelled probes. The probes are specific for sequence polymorphism associated with the genotype and are attached to either a Micro Bead or a Solid Phase. In addition, the detection of single nucleotide polymorphism(s) which "tag" for the genotype using a real-time PCR is described.

ERAP1 polymorphisms and haplotypes are associated with ankylosing spondylitis susceptibility and functional severity in a Spanish population

OBJECTIVES

The aim of this study was to assess the involvement of the endoplasmic reticulum aminopeptidase 1 (ERAP1) gene in AS susceptibility and functional severity in a Spanish population.

METHODS

Eight single nucleotide polymorphisms (SNPs) spanning the ERAP1 gene were genotyped by allele-specific fluorescent PCR in 300 AS Spanish patients and 300 spondylarthritis-free controls. The influence of the ERAP1 SNPs on the functional severity of AS was analysed with the BASFI corrected for disease duration. Association analyses with AS susceptibility and functional severity were performed.

RESULTS

Significant ERAP1 single marker association with AS susceptibility was found for five SNPs, namely rs30187 (allele T: P = 0.035), rs17482078 (allele C: P = 0.030), rs2287987 (allele T: P = 0.028), rs26653 (allele C: P = 0.041) and rs10050860 (allele C: P = 0.018). Three of the associated SNPs (rs17482078, rs2287987 and rs10050860) were in strong linkage disequilibrium. After imputing genotypes with the HapMap CEU data as reference, the strongest association was with rs41135 (P = 0.0046) in the 5'-upstream region of ERAP1. In addition, the SNP rs17481856 was found to be a risk factor for functional severity in AS and a borderline trend was observed for rs27044.

CONCLUSIONS

These results suggest that the ERAP1 gene is associated with genetic predisposition to AS and influences the functional severity of the disease in a Spanish population.

Rapid HLA-B27 screening with real-time TaqMan PCR: a clinical validation in the Dutch population

Human leukocyte antigen B27 (HLA-B27) is strongly associated with ankylosing spondylitis. The B27 allele is present in 90% of patients with this disease, whereas it is present in only 9% of Caucasians. Molecular detection of HLA-B27 is traditionally based on allele specific amplification of exon 2 (Olerup method) or exon 3 (Dominguez method) by PCR, followed by gel analysis.

We developed a real-time TaqMan PCR based on the Dominguez method with a β-Globin PCR as internal control.

A total of 544 clinical samples were used to compare the real-time TaqMan PCR with the traditional Dominguez PCR, the traditional Olerup PCR and a commercial Olerup based HLA-B27 detection kit (

With a correct result for 543 out of 544 samples (99.8%), we consider our real-time HLA-B27 PCR is a reliable method to detect HLA-B27 in the Dutch population, with reduced hands-on time and contamination risk compared to traditional PCR methods.

Association of the intergenic single-nucleotide polymorphism rs10865331 (2p15) with ankylosing spondylitis in a Spanish population

OBJECTIVE

A recent genome-wide association study has identified 2 single-nucleotide polymorphisms (SNP) associated with ankylosing spondylitis (AS), rs10865331 (2p15) and rs2242944 (21q22). We assessed the association of these SNP with AS in a Spanish population.

METHODS

Four hundred fifty-six patients with AS fulfilling the modified New York Criteria and 300 healthy donors were analyzed. Result. SNP rs10865331 (allele A: p = 0.039; genotype: p = 0.016) was significantly associated with AS, while no association was found for rs2242944.

CONCLUSION

This is the first study that replicates in an independent cohort the association of the intergenic SNP rs10865331 with susceptibility to AS.

Human plasmacytoid dendritic cells from patients with chronic hepatitis B virus infection induce the generation of a higher proportion of CD4(+) and CD25(+) regulatory T cells compared with healthy patients

This study was undertaken to investigate whether plasmacytoid dendritic cells (PDC) are involved in the generation of a higher proportion of CD4(+) and CD25(+) regulatory T (Treg) cells in chronic hepatitis B virus (HBV) infection compared with healthy patients. The amount, phenotype, and function of Treg cells in CD4(+) T cells primed by PDC from 46 chronic HBV patients, 25 healthy controls, and 10 individuals with resolved HBV infection were studied by flow cytometry, reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, and proliferation assay. CD4(+) T cells primed by PDC from chronic HBV patients were more effective than CD4(+) T cells primed by PDC from the healthy controls and the resolved HBV patients in suppressing the hepatitis B core antigen-specific proliferation and the interferon production. The interleukin-10 and transforming growth factor-beta1 could also be detected in the supernatants of the PDC-primed CD4(+) T cells. A higher percentage of Treg cells, defined as CD4,CD25, CD45RO, and cytotoxic T-lymphocyte-associated antigen 4-positive cells, was detected within the population of CD4(+) T cells primed by PDC from chronic HBV patients compared with the healthy controls and individuals with resolved HBV infection. Accordingly, CD25(+) Treg cells from PDC-primed CD4(+) T cells displayed a high Fox P3 messenger RNA level. Depleting CD4(+) and CD25(+) Treg cells from CD4(+) T cells primed by PDC from the chronic HBV patients, the healthy volunteers, and the resolved HBV patients made PDC-primed CD4(+) T lose the capability in suppressing HBV-specific T cells. PDC from the patients with chronic HBV infection induced the generation of a higher proportion of CD4(+) and CD25(+) Treg cells compared with the healthy patients.

Long-term stabilized blood samples as controls for flow cytometric HLA-B27 screening: a feasibility study

BACKGROUND

Long-term stabilized blood samples are potentially useful as positive or negative procedure controls for flow cytometric HLA-B27 screening, and could serve as test samples in an external quality assessment (EQA) scheme. We evaluated long-term stabilized whole blood specimens as prepared for the UK NEQAS for Leucocyte Immunophenotyping EQA scheme (Sheffield, UK).

METHODS

Peripheral blood samples were obtained from nine blood bank donors with known HLA-B typing. Short-term stabilization with Trans-FIXtrade mark was performed before shipment to Sheffield. Thereafter, long-term stabilization was performed. Commercially available HLA-B27 mAb were tested periodically between 1 week and 12 months on (i) fresh, (ii) short-term stabilized, and (iii) long-term stabilized blood samples using a stain, lyse, and wash technique. We compared the forward scatter (FSC), sideward scatter (SSC), and fluorescence signals of lymphocytes as a function of time. Furthermore, a pilot send-out with stabilized blood samples of four blood bank donors was distributed among the participants to the Benelux EQA scheme for HLA-B27 screening, and results were compared with historical EQA data obtained using nonstabilized blood samples from the same donors.

RESULTS

There were no major effects on FSC and SSC characteristics of lymphocytes. Background fluorescence of stabilized samples increased and specific fluorescence of stabilized HLA-B27 positive samples decreased as compared with fresh samples. However, discrimination between the investigated HLA-B27 positive and HLA-B27 negative samples remained feasible poststabilization. In the pilot send-out, the results obtained with stabilized samples were less concordant than with the corresponding fresh samples due to variable quality of the stabilized samples.

CONCLUSION

Long-term stabilized whole blood samples are potentially useful as true HLA-B27 positive and true HLA-B27 negative control cells for daily and longitudinal quality control of flow cytometric HLA-B27 screening. In the same way, long-term stabilized samples may be used for EQA purposes. However, these samples are currently not feasible for reagent validation purposes. Extensive quality control of long-term stabilized samples is necessary before distribution in multicenter surveys.

EQUAL-qual: a European program for external quality assessment of genomic DNA extraction and PCR amplification

BACKGROUND

Despite the rapid transition into routine clinical practice of molecular techniques based on PCR, external quality assessment (EQA) is still not widely available. The European Union and European Communities Confederation of Clinical Chemistry have supported the EQUAL project as a series of 3 different EQA programs for the assessment of molecular methods independently from analytes. We present the results from the EQUAL-qual program designed to evaluate the analytical aspects of DNA analysis by means of a conventional qualitative PCR experiment.

METHODS

The EQUAL-qual program provided DNA, blood samples, and primer sets to participant laboratories to assess DNA extraction and PCR amplification. We have developed statistical procedures to identify laboratories performing poorly in DNA extraction (quality and quantity), PCR efficiency, and data interpretation after electrophoresis.

RESULTS

An application to participate was obtained from 213 laboratories (from 25 countries), and 175 (82%) of laboratories submitted results for assessment. Questionable results in terms of quality and/or quantity of DNA derived from blood extractions were returned by 27% of laboratories (46 of 166). PCR efficiency showed high variability, with 3% of laboratories (5 of 163) showing a consistently low rate of amplification and 10% (18 of 175) not reporting the expected number of bands of the amplified targets.

CONCLUSIONS

The results showed considerable variability in all phases of the experiment. The approach confirms the validity of EQA as a method for evaluating analytical aspects of PCR-based tests.

A simple and practical agglutination assay for human leucocyte antigen-B27 typing

BACKGROUND AND OBJECTIVES

The human leucocyte antigen (HLA) B27 is the most frequently typed single antigen that is associated with diseases. Here, we describe a simple and rapid particle agglutination assay (PaGIA) for HLA-B27 typing.

MATERIALS AND METHODS

Superparamagnetic particles were coated with a monoclonal antibody to HLA-B27 and subsequently used for testing. Anticoagulated whole-blood samples were obtained from healthy blood donors (n = 194) with known HLA patterns and from patients (n = 51) who had been typed positive for HLA-B27 by flow cytometry.

RESULTS

The particles agglutinated only after incubation with HLA-27-positive blood samples, using the ID-microtyping system. Positive reactions were clearly distinguishable from negative reactions in all samples tested. Flow cytometric HLA-B27 typing revealed an indeterminate result in one patient.

CONCLUSIONS

The new HLA-B27 PaGIA is suitable for rapid typing of HLA-B27. The assay is simple and easy to perform, and can be implemented in any routine laboratory.

Polymorphism of HLA-DRB1 gene shows no strong association with ulcerative colitis in Chinese patients

The genetic factors predisposing to ulcerative colitis (UC) have remained totally unclear to date. This study aimed to investigate the role of HLA-DRB1 genetic polymorphism in the susceptibility to develop UC in Chinese patients. HLA-DRB1 genotyping was carried out in 72 unrelated patients with UC and 314 healthy controls by using polymerase chain reaction-sequence-specific primers (PCR-SSP). All of the patients and healthy controls are Han people in China. The frequency of DRB1*07 allele was increased in UC patients compared with healthy controls (19.4% vs. 9.2%, P = 0.0229, OR = 2.372, 95%CI: 1.181-4.766), but the significance disappeared when given Bonferroni correction (P(C) = 0.2977). Furthermore, compared with healthy controls, although HLA-DRB1*07, DRB1*16/DRB1*09 and DRB1*07/DRB1*12 genotypes were increased in frequency in the patients with extensive colitis, and the patients without extraintestinal manifestations (EIMs) carried an increased frequency of HLA-DRB1*07 and DRB1*07/DRB1*12 genotypes, these differences did not reach statistical significance after Bonferroni correction. HLA-DRB1 alleles showed no strong association with UC, and no HLA-DRB1 alleles or genotypes were strongly associated with clinical subgroups of UC in Chinese patients.

HLA-B27 testing in Thai patients using the PCR-SSP technique

We develop the HLA-B27 test kit using the PCR-SSP technique. Five hundred forty blood samples were tested for HLA-B27 by microlymphocytotoxicity test (LCT) and PCR-SSP. It was found that 127 (23.5%) and 134 (24.8%) of these samples were positive for HLA-B27 by LCT and PCR-SSP, respectively. The sensitivity and specificity of the PCR-SSP were 94.8 and 100%, respectively, when using LCT as the standard method. The PCR-SSP positive predictive value was 100%, negative predictive value was 98.3%, and a concordance rate of 98.7%. This study shows that the PCR-SSP is simple, convenient, and a more cost-effective in-house test kit.

Rapid detection of all HLA-B*27 alleles (B*2701-B*2725) by group-specific polymerase chain reaction

Human leucocyte antigen-B*27 is strongly associated with a number of rheumatic diseases, including ankylosing spondylitis and reactive arthritis. Targeted detection of the B*27 group by molecular methods is hampered by the extreme heterogeneity of the serological B*27 group. Here, we describe a simple, rapid sequence-specific primer-based method for detection of all 28 B*27 alleles defined to date. The method involves an initial screening with two sequence-specific polymerase chain reactions (PCRs), which has to be followed by two additional PCR amplifications in samples carrying a few rare subtypes of B*27, B*4202 or B*7301. The described protocol should be useful for laboratories involved in diagnostics and research of rheumatoid diseases.

HLA-B27 genotyping by Fluorescent Resonance Emission Transfer (FRET) probes in real-time PCR

Several polymerase chain reaction (PCR)-based human leukocyte antigen (HLA) genotyping methods are in use, but none is fully satisfactory. The introduction of real-time PCR (rt-PCR) with fluorescence resonance energy transfer (FRET) probes provides a powerful tool to overcome the drawbacks of current methods such as the long processing time and the requirement for post-PCR manual procedures. Here we present evidence that the FRET-fluorotyping principle may resolve HLA-B27 variants, providing a higher resolution in less time than the techniques currently in use. The protocol uses between one and three consecutive amplification reactions depending on the resolution required. The first reaction, aimed at detecting HLA-B27-positive samples, uses beta-globin coamplification as control. The second reaction, aimed at resolving most frequent B27 alleles, uses two hybridization probes whose melting temperatures curves allow the classification of HLA-B27 alleles into eight groups. By adding a third reaction, even the rarest alleles associated and not associated to ankylosing spondylitis (AS) may be discriminated. The technique was blindly tested on 60 samples from individuals previously typed and confirmed by standard PCR sequence-specific oligoprobes-PCR sequence and PCR-based typing PCR-SBT (30 B27+, 30 non-B27). There was a complete concordance rate, thus confirming the potential of this new technique for clinical HLA-B27 typing and for HLA typing in general.

Rapid screening for HLA-B27 by a TaqMan-PCR assay using sequence-specific primers and a minor groove binder probe, a novel type of TaqMan trade mark probe

HLA-B27 is strongly associated with ankylosing spondylitis (AS). As typing for HLA-B27 is routinely performed by serological methods, false-positive results can be generated. Therefore, several more accurate molecular methods have been developed for HLA-B27 genotyping. We describe a real-time PCR method for the detection of the HLA-B27 allele using sequence-specific primers (SSP) combined with a fluorogenic MGB probe (minor groove binder probe), a novel type of TaqMan probe. The MGB increases the melting temperature (T(m)) of the probe, allowing the use of shorter probes. Moreover, the use of a non-fluorescent quencher (NFQ) attached to the MGB probe improves the efficiency of fluorescence quenching, thus providing a very low fluorescent background. We tested this method on 150 subjects (41 HLA-B27 positive and 109 HLA-B27 negative) who underwent routine HLA-B27 serological testing by flow cytometry (FC). Serology and our TaqMan assay gave identical results in all cases and no false positive or negative results were observed. A graphical representation of fluorescence and normalized reporter signal (DeltaRn) values demonstrated that HLA-B27 positive and HLA-B27 negative samples formed two tight clusters making it possible to clearly differentiate between HLA-B27 positive and negative samples. This single tube PCR method for the detection of HLA-B27 should be particularly suitable for the routine analysis of large numbers of samples in the laboratory.

Roles of HLA-B, HLA-C and HLA-DPA1 incompatibilities in the outcome of unrelated stem-cell transplantation

In unrelated stem-cell transplantation, the value of matching at the HLA-A, -B and -DR loci between donor and recipient is well documented. The effect of HLA-C, DPB1 and DPA1 mismatches on transplantation outcome is unclear. In this study, 104 donor recipient-pairs, transplanted at Huddinge University Hospital between 1988 and 1999, were retrospectively HLA class I- and class II-typed by PCR-SSP. The samples were typed for HLA-A, -B and -C and HLA-DRB1, -DRB3, -DRB4, -DRB5, -DQA1, -DQB1, -DPB1 and -DPA1 with allele level resolution. Isolated HLA-B allele level mismatches were associated with an increased incidence of acute graft versus host disease grades II-IV and grades III-IV. HLA-C-mismatched, but killer cell immunoglobulin-like receptor (KIR) ligand motif-matched stem-cell grafts were significantly associated with improved survival rates and relapse-free survival (RFS). In patients receiving HLA-DPA1-mismatched stem cell grafts, reduced survival and shorter RFS were seen. These patients also had an increased frequency of relapses (64%vs 26%). We conclude that genomic HLA class I- and class II-typing may improve the outcome after unrelated stem-cell transplantation. The awareness of HLA class I- and II-mismatches in a recipient-donor pair makes it possible to give appropriate pre- and post-transplantation treatment.

Flow cytometric HLA-B27 screening: cross-reactivity patterns of commercially available anti-HLA-B27 monoclonal antibodies with other HLA-B antigens

BACKGROUND

Some 50 clinical laboratories in the Benelux perform flow cytometric HLA-B27 screening and participate in the Benelux external quality assessment scheme operational since 1995. Results from this scheme indicate that cross-reactivity of HLA-B27 monoclonal antibodies (mAbs) is a major problem.

METHODS

We analyzed cross-reactivity patterns of commercially available mAbs for HLA-B27 screening. Three clones of HLA-B27 mAb (ABC-m3, n = 3; FD705; and GS145.2) from five manufacturers were evaluated. Test cells were selected as to express HLA-B antigens with known serologic cross-reactions (HLA-B7, B12, B13, B16, B17, B22, B37, B40, B41, B42, B47, and B48). Cells without B27 cross-reactive antigens (B5, B8, B14, B15, B21, and B35) and cells positive for B27 were included as controls. All tests were performed and interpreted as recommended by the manufacturers. Cross-reactivity was defined as increased fluorescence intensity in comparison with the baseline reactivity observed with the corresponding immunoglobulin G isotype control mAb.

RESULTS AND CONCLUSIONS

All mAbs tested showed cross-reactivity, ranging from weak (+/-) to strong (+), with different antigens and different degrees of intensity-ABC-m3: (+/-) B12, B16, B17, B41, B47, and B48 and (+) B7, B13, B22, B37, B40, and B42; GS145.2: (+/-) B13, B17, B22, B40, and B47 and (+) B7, B16, B37, B42, and B48; FD705: (+/-) B12, B13, B16, and B48 and (+) B17, B37, and B47. If one mAb had been used for HLA-B27 screening, ABC-m3 would have yielded nine false-positive B27 assignments, FD705 would have yielded seven, and GS145.2 would have yielded two. This problem largely canbe avoided by the combined use of two different mAb clones. The combination of FD705 and GS145.2 yielded the best results, with one false-positive HLA-B27 assignment among the 99 HLA-B27(-) samples of this highly selected panel.

B*27 in molecular diagnostics: impact of new alleles and polymorphism outside exons 2 and 3

HLA-B*27 is known to be associated with ankylosing spondylitis and several methods have been applied to determine its presence or absence. In this report two molecular methods were used for detection of B*27. The polymerase chain reaction sequence-specific primer (PCR-SSP) method was performed to detect the presence or absence of B*27, whereas the sequence-based typing method (SBT) was used to identify the B*27 subtype. The PCR-SSP method used to detect B*27 was updated to enable the detection of all B*27 alleles. The typing results obtained by this method were compared with the serological typings of 262 individuals. Fifty of them were found to be B*27 positive by PCR-SSP and 46 also showed positive serological reactions with B27-specific sera. The four discrepancies were the result of the presence of B*2712 in three individuals and B*2715 in one individual; both alleles showed no serological reactions with B27-specific antisera. With SBT the sequences of exons 1 through 4 were determined to unequivocally assign the B*27 alleles. Eleven different subtypes were detected in 78 individuals, including three new B*27 alleles: B*27054, B*2715 and B*2717. The allele B*27054 showed an allelic drop out when exon 3 was amplified. Three differences with B*27052 were demonstrated; one in exon 1, one in intron 1 and one in intron 2, the latter being responsible for the allelic drop out. The B*2715 allele was serologically not detectable with several B27-specific sera, but showed Bw4-positive reactions. The sequence of B*2715 showed two mismatches with B*2704. The sequence of B*2717 showed one mismatch with B*27052 at position 248 (A-->T), which was considered to be a conserved position in all B alleles.

HLA-DPB1 typing by polymerase chain reaction amplification with sequence-specific primers

DPB1 is the second most polymorphic class II locus with currently 84 recognized alleles, i.e. DPB1*0101 to DPB1*8101. Most of the alleles have been described during the last few years using oligonucleotide and sequencing techniques and relatively little is known about the role and importance of the polymorphic residues as regards to the function of DP molecules. In the present study, polymerase chain reaction (PCR) primers were designed for identification of all the phenotypically different DPB1 alleles by PCR amplification with sequence-specific primers. Forty-eight standard genomic PCR reactions per sample were performed in order to achieve this resolution. Unique amplification patterns were obtained in 2983 of 3160 (94.4%) possible genotypes. The primers were combined so that only very rare genotypes gave rise to ambiguous patterns. Sixty-four Histocompatibility Workshop cell lines and 150 DNAs provided by the UCLA DNA exchange were investigated by the DPB1 primer set. All typing results were conclusive. Analysis of the distribution of DPB1 alleles was performed in 200 Caucasian samples, 100 African samples and 40 Oriental samples. The population study by the DPB1 PCR-SSP method showed a characteristic distribution of HLA-DPB1 alleles. Each ethnic group had one, or two, frequent DPB1 allele(s) and the frequency of homozygotes was high, suggesting that balancing selection does not appear to be affecting the evolution of the DPB1 locus.

Direct amplification of rRNA genes in diagnosis of bacterial infections

A broad-range bacterial PCR targeting rRNA genes (rDNAs) was used to directly analyze 536 clinical samples obtained from 459 hospitalized patients during a 4-year study period. The molecular diagnosis based on DNA sequencing of the PCR product was compared to that obtained by bacterial culture. The bacteriological diagnosis was concordant for 447 (83%) specimens. Broad-range rDNA PCR was the only method that yielded an etiologic diagnosis for 11 (2.4%) of 459 patients. Compared to culture and clinical assessment, the sensitivity of the PCR method combined with sequencing was 74.2%, and the specificity was between 98.7 and 99.6%. At present, the described molecular approach proved superior to bacterial culture in two clinical situations: infections caused by bacteria with unusual growth requirements and specimens taken during antimicrobial treatment of the patient.

HLA-B*27 typing by sequence specific amplification without DNA extraction

HLA-B27 appears to play a direct role in the pathogenesis of ankylosing spondylitis and almost all patients with this disease have HLA-B27. Therefore, a diagnosis of ankylosing spondylitis can virtually be excluded in the absence of HLA-B27. Many techniques have been used for HLA-B*27 typing. Of these, molecular methods are the most sensitive and specific but require extracted DNA as the testing material. A technique where HLA-B*27 is amplified directly from whole blood using sequence specific primers has been developed. This technique uses small sample volumes, is not restricted by choice of anticoagulant or sample age up to at least six weeks, and can be applied to other clinical polymerase chain reaction based procedures.

Variability in the interpretation of microsatellite patterns with different electrophoretic conditions

Microsatellite markers permit the analysis of microsatellite instability and loss of heterozygosity. Frequently, the allelotypes of microsatellites are interpreted in the presence of numerous bands in gels. The importance of different gel electrophoresis conditions in the interpretation of microsatellite patterns was tested. Microsatellite markers were used to amplify DNA from gastric cancer samples and adjacent gastric mucosa. Polymerase chain reaction (PCR) products were separated by electrophoresis through 7% polyacrylamide gels containing either 5.6 M urea and 32% formamide or 7 M urea. PCR reactions separated on urea/formamide gels resulted consistently in clear allele definition (one or two bands), whereas 7 M urea gels resulted in allele patterns that comprised multiple bands. Analysis of microsatellite abnormalities using nonformamide gels gave false negative results in just under a third of cases (four of 13). In conclusion, the interpretation of microsatellite alterations in cancer DNA is improved by using electrophoresis conditions that result in complete DNA denaturation, such as urea/formamide/acrylamide gel electrophoresis.

The immunogenetics of the seronegative spondyloarthropathies

In none of the rheumatic diseases has the genetic contribution to pathogenesis been so well characterized as in the seronegative spondyloarthropathies. Most important has been the elucidation of the structure and effect on disease expression of HLA-B27, where 11 subtypes have been distinguished to date. These vary in frequency in different ethnic groups and seem to show differential disease associations. The high frequency of this gene in patients with the seronegative spondyloarthropathies, especially ankylosing spondylitis (AS) and Reiter's syndrome (RS)/reactive arthritis (ReA), has emerged as probably the best example of a disease association with a hereditary marker. Other HLA genes, in addition to HLA-B27, have been implicated in psoriasis and psoriatic arthritis. These include those from the HLA-C locus and from HLA-DR. In addition, recent family studies have implicated other genes outside the MHC that further enhance the susceptibility to AS.

Fluorotyping of HLA-A by sequence-specific priming and fluorogenic probing

The aim of our study was to develop a fluorotyping strategy for the HLA-A locus. In contrast to conventional sequence-specific primed PCR (PCR-SSP), which is based on an agarose gel electrophoresis, fluorotyping eliminates the drawback of low sample throughput, low potential for automation and problems related to contamination. Additionally, fluorotyping is capable of delivering quantitative results depending on the system set-up. The fluorescence-based PCR-SSP assay relies on target-specific and individually labeled fluorogenic probes allowing a simultaneous and differential detection of the specific HLA and the internal control product. The probe used to detect the HLA-A specific amplicons was labeled at its 5' end with 6-carboxyfluorescein (FAM) as the reporter and at its 3' end with 6-carboxy-tetramethylrhodamine (TAMRA) as the quencher. The probe hybridized within the 2nd intron to a conserved region which was found to be identical in all HLA-A alleles and was covered by all primer mixes. During successful PCR the cleavage of the FAM-labeled probe through the 5'-3' exonuclease activity of the Taq DNA-polymerase led to an interruption of the TAMRA-mediated quenching effect and generated a significant increase of the FAM fluorescence. The specific HLA-A typing information was based on the FAM fluorescence released by 24 individual PCR primer mixes. The internal control amplicon was detected with a tetrachloro-6-carboxyfluorescein-TAMRA-labeled fluorogenic probe. Since the HLA-A amplicons had to include the 2nd intron as the target for the fluorogenic probe, the sequence motifs which could be used as priming sites were limited. Therefore, some primer mixes covered more than one specificity resulting in ambiguous amplification patterns in 31 of 231 possible allele or group combinations of HLA-A1-A80. These ambiguities, which all involved the inability to discriminate a particular heterozygous genotype from a homozygous genotype, may be resolved by the quantitative data revealed by fluorotyping. This feature is also helpful to detect new alleles which are not amplified by the current primer mixes.

Detection of HLA-B27 alleles by group-specific amplification and time-resolved fluorometry

This newly developed HLA-B27 assay combines a polymerase chain reaction (PCR) from blood spot samples with solution hybridisation in microtitration plate and with time-resolved fluorometry (TRF) as the detection system. In a multiplex amplification reaction, the 144 base pair region of HLA-B27 alleles is amplified with allele-specific primers simultaneously with the region of beta-actin gene as an internal control. Amplified products are collected onto streptavidin (SA)-coated microtitration wells, denatured and hybridised with a europium (Eu)-labelled HLA-B27 specific probe and a samarium (Sm)-labelled beta-actin specific probe. Finally, Eu and Sm fluorescence is enhanced and detected in a time-resolved fluorometer. The typing results obtained with 110 blood spot samples showed an exact match with serological class I HLA-typing. When this technique was further evaluated, 348 blood spot samples were clearly categorised into two populations, HLA-B27 positives and negatives. This new PCR-TRF method permits the automation of HLA-B27 assays and saves time and labour in routine diagnostics.

HLA-B27 and the seronegative spondyloarthropathies

In the 25 years since the initial reports of the association of HLA-B27 with ankylosing spondylitis (AS) and subsequently with Reiter's syndrome, psoriatic spondylitis, and the spondylitis of inflammatory bowel disease, the association of HLA-B27 with the seronegative spondyloarthropathies has remained one of the best examples of a disease association with a hereditary marker. HLA-B27 has been recognized as representative of a spectrum of diseases, ranging from the majority of HLA-B27-positive individuals who have no disease at all, through those with isolated eye or skin involvement, to those with critical eye, heart, and peripheral joint compromise of full-blown AS. Yet HLA polymorphism has evolved in response to environmental stresses, and even the presence of HLA-B27 itself appears to confer advantages in certain infectious diseases, such as acquired immune deficiency syndrome (AIDS). This article will review what is currently known about HLA-B27 and disease, especially in the seronegative spondyloarthropathies. The structure-function relationship of HLA-B27 will be presented, including differences between the B27 subtypes both in their ethnic variation and possible disease implications. The disease spectrum conferred by the presence of HLA-B27 will also be discussed, and the theories of how HLA-B27 contributes to the pathogenesis of the spondyloarthropathies will be considered.

HLA-B*27 typing by group-specific hybridization in microtiter plates

We have developed and evaluated a test for HLA-B*27 based on PCR and DNA hybridization in microtiter plates. A region within exon 2 of the HLA-B gene is amplified and labeled by PCR and the amplification product is hybridized to a group-specific HLA-B*27 and a generic control oligonucleotide probe in two separate cavities of the plate. Bound sequences are detected using an ELISA-like protocol. The assay has been evaluated on 254 DNA samples routinely received for B27 testing in parallel with serological and SSP-PCR typing. Results were concordant in typing 102 HLA-B27-positive and 152 HLA-B27-negative individuals except for two samples containing HLA-B*73, which stained B27 positive in the microwell test. The new procedure is rapid and simple to perform, and the microwell format is particularly suitable for automation.

Localised sequence regions possessing high melting temperatures prevent the amplification of a DNA mimic in competitive PCR

The polymerase chain reaction is an immensely powerful technique for identification and detection purposes. Increasingly, competitive PCR is being used as the basis for quantification. However, sequence length, melting temperature and primary sequence have all been shown to influence the efficiency of amplification in PCR systems and may therefore compromise the required equivalent co-amplification of target and mimic in competitive PCR. The work discussed here not only illustrates the need to balance length and melting temperature when designing a competitive PCR assay, but also emphasises the importance of careful examination of sequences for GC-rich domains and other sequences giving rise to stable secondary structures which could reduce the efficiency of amplification by serving as pause or termination sites. We present data confirming that under particular circumstances such localised sequence, high melting temperature regions can act as permanent termination sites, and offer an explanation for the severity of this effect which results in prevention of amplification of a DNA mimic in competitive PCR. It is also demonstrated that when Taq DNA polymerase is used in the presence of betaine or a proof reading enzyme, the effect may be reduced or eliminated.

TAP2 alleles in inflammatory arthritis

Sixty patients with reactive arthritis (ReA) and 40 with rheumatoid arthritis (RA), were typed for H LA-B27 and class II antigens DR and DQ, and studied for TAP2 gene polymorphism in comparison with 60 healthy controls. TAP2 polymorphisms at positions 379, 565, 665, and 687 were analyzed using amplification refractory system-based PCR and polymorphisms at positions 386 and 651 using oligonucleotide hybridization. The frequency of the TAP2A/A genotype was 30%(12/40) in RA, in contrast to 13% (8/60) in the controls. This genotype was further associated with DRB1*04 positive RA (10/24, 42%, P=0.01), as well as the TAP2A allele (31/48, 65%, P =0.012). Thr/Thr dimorphism at TAP2 position 665 (24/40, 60%, P=0.024) and Stop/Stop dimorphism at TAP2 position 687 (24/40, 60%, P=0.024) were found to be increased in RA patients as compared to controls. When TAP2I/J polymorphism was studied, TAP2J positivity was found associated with the HLA-B27DR4-DQB1*0301-haplotype in ReA patients. 9/12 of these were positive as compared to 20/60 in random controls (P=0.010). Polymorphisms of the TAP2 gene were found to be associated with subgroups of RA and ReA patients with disease associated markers (e.g. TAP2A in DRB1*04 positive RA, or TAP2J in HLA-B27-DRB1*04-DQB1*0301 positive ReA). These may thus serve as additional markers of specific haplotypes associated with susceptibility to inflammatory arthritis.

Ten-year experience in transplantation of A2 kidneys into B and O recipients

BACKGROUND

This article summarizes our 10-year multicenter experience with transplantation of 50 blood group A2 and A2B kidneys into B and O patients.

METHODS

Since 1986, we have transplanted kidneys from 46 cadaver donors and 4 living donors who were blood group A2 (47 donors) or A2B (3 donors) into 19 B and 31 O patients. In 1991, we began allocating these kidneys preferentially to B and O recipients who were selected based on a history of low (< or =4) anti-A IgG isoagglutinin titers. Immunosuppression was no different from that used in ABO-compatible grafts.

RESULTS

The 1-month function rate before thus selecting the patients was 68% (19/28), but is now 94% (17/18). Two-year cadaver-donor graft survival with this selection method is 94%, compared with 88% for 640 concurrent and consecutive ABO-compatible transplants (log-rank, 0.15). All four living-related transplants are still functioning, with a mean follow-up of 71 months. Since we began allocating A2 kidneys preferentially to B and O recipients, the percentage of the B patients who received A2 or A2B kidneys has increased from 29% (8/28) to 55% (10/18).

CONCLUSIONS

Transplantation of A2 or A2B kidneys into B and O patients is clinically equivalent to that of ABO-compatible transplantation when recipients are selected by low pretransplant anti-A titer histories. This approach increases access of blood group B recipients to kidneys.

Invasion and persistence of Salmonella in human fibroblasts positive or negative for endogenous HLA B27

OBJECTIVE

Analysis of the interaction of enteropathogenic bacteria with HLA B27 transfected murine fibroblasts showed a specific influence of HLA B27 on microbial invasiveness. This possible novel mechanism for the action of HLA B27 should be verified by using endogenous HLA B27 positive and negative human fibroblasts as a model for the direct interaction of arthritogenic bacteria and host cells.

METHODS

Fibroblasts were obtained from healthy donors positive or negative for HLA B27; cultivated as monolayers; and infected with Salmonella enterica serovar enteritidis.

RESULTS

Invasion and survival of bacteria in human cells was not influenced by the presence of HLA B27. Enhancement of HLA class I molecule expression by treatment of cultures with interferon gamma decreased invasion and survival of bacteria in both HLA B27 positive and negative cells. After disappearance of live bacteria lipopolysaccharide antigens persisted within cells.

CONCLUSION

Endogenous HLA B27 does not modulate the direct interaction of Salmonella with human cells. Non-professional phagocytes are able to limit bacterial survival in cells, and interferon gamma accelerates killing of bacteria, but arthritogenic antigens persist after disappearance of live bacteria.

Error rate for HLA-B antigen assignment by serology: implications for proficiency testing and utilization of DNA-based typing methods

Until recently, the majority of HLA class I typing has been performed by serology. Expensive commercial typing trays are frequently used for testing non-Caucasian subjects and new strategies using DNA-based methods have been adopted for improving clinical histocompatibility testing results and adapted as supplements in proficiency testing. A double-blind comparison of the typing of HLA-B specificities in 40 samples was carried out between serology and two polymerase chain reaction (PCR) methods, PCR amplification with sequence-specific primers (PCR-SSP) and PCR amplification and subsequent hybridization with sequence-specific oligonucleotide probes (PCR-SSOP). The results demonstrated 22.5% misassignments of HLA-B antigens by serology. There was complete concordance between the results obtained with the two PCR based typing methods. A second panel of 20 donor samples with incomplete or ambiguous serologic results was analyzed by PCR-SSP and SSOP Both PCR methods identified correctly the HLA-B antigens. Our results suggest that more accurate typing results can be achieved by complementing serologic testing with DNA-based typing techniques. The level of resolution for HLA-B antigen assignment can be obtained by this combination of serology and limited DNA-based typing is equivalent to the HLA-B specificities defined by the WHO-HLA Committee. This level of resolution cannot routinely be achieved in clinical histocompatibility testing or in proficiency testing using serologic reagents only.

DNA typing of HLA-B27 by polymerase chain reaction

To find a specific method for HLA-B27 typing, we tested an HLA-B27-specific polymerase chain reaction. This method was used for screening 100 randomly selected blood donors, 10 of them being HLA-B27 positive. A flow cytometric method and this PCR method were compared.

Sequencing of HLA class I genes based on the conserved diversity of the noncoding regions: sequencing-based typing of the HLA-A gene

We present a sequencing-based typing strategy for the HLA-A locus that is generally applicable to all HLA class I genes. Sequencing-based typing is the method of choice for matching in unrelated bone marrow transplantation on the allelic level. We determined the noncoding sequences of all serological antigens and most of their subtypes and discovered a remarkably conserved diversity characterized by polymorphic sequence motifs. In this study we took advantage of this diversity we uncovered in the 5' flanking region, 5' untranslated region and in the introns 1, 2 and 3, which was related to serological families. We established 12 primer mixes for setting up a PCR-based template preparation. Our strategy is based on the separate amplification of haplotypes and therefore defines the cis/trans linkage of polymorphic sequence motifs. This allowed individual sequencing of the haplotypes in all samples heterozygous for the broad antigens as well as the complete analysis of the polymorphic exons 2 and 3. All templates included the 2nd intron which was used as a priming site for the gene-specific 5' and 3' universal sequencing primers regardless of the amplified haplotypes. The independent sequencing of the haplotypes allows the application of the dye terminator cycle sequencing technique, which is less time-consuming and less-laborious than dye primer chemistry. The lack of heterozygous positions essentially facilitates on the one hand the data analysis and on the other hand the detection of new alleles. Sequencing is only required in one direction due to the absence of peak shift problems. The results will remain unambiguous regardless of a growing HLA sequence data bank since this sequencing technique defines the cis/trans linkage of sequence motifs in more than 95% of the cases.

HLA-B*27 typing by PCR-restriction fragment length polymorphism

In this study we describe the use of PCR-RFLP for genotyping HLA-B*27. A 557 bp fragment from HLA-B locus is amplified and subjected to digestion with StyI. The presence of B*27 is detected on electrophoresis by the appearance of 431 + 126 bp pattern. The same pattern could be obtained only for the very infrequent allele B*7301. However, this allele was not amplified in the B73 sample tested with the primers and conditions used in this study. Nevertheless, we have designed two PCR-RFLP approaches for separating these alleles. The PCR-RFLP method was tested on a panel of forty-three cell lines and applied to fifty spondyloarthritic patients and one-hundred-eighty healthy subjects. Given its robustness, technical simplicity and cost-effectiveness, we think that this method can be incorporated for routine use in most laboratories.

HLA markers and prediction of clinical course and outcome in rheumatoid arthritis

OBJECTIVE

To evaluate HLA markers as early prognostic factors for disease severity in rheumatoid arthritis (RA).

METHODS

HLA genotyping was carried out in a retrospective analysis of 66 RA patients and in a prospective study of 55 RA patients and 87 healthy controls using polymerase chain reaction-based methods for HLA-DRB1 specificities, DR4 alleles, and their linked DQB1 alleles, as well as HLA-B27. The clinical course of RA was assessed by clinical and radiologic scores. The impact of HLA markers was evaluated by epidemiologic means in addition to modeling using multiple logistic regression analysis.

RESULTS

Shared epitope-positive (HVR3+) DR4 alleles and the HVR3 amino acid cassette QKRAA were associated with RA in both longstanding (relative risk [RR] 3.34 and 3.19) and recent-onset (RR 2.1 and 2.37) RA. In longstanding RA, radiologic evidence of severe joint destruction (Larsen score > 1.62) was seen more often in HVR3 shared epitope-positive patients than in epitope-negative patients (odds ratio [OR] = 25.67, chi 2 = 13.59, P = 0.0003). Moreover, rank sum analysis of Larsen indices indicated significantly higher ranking for the presence of the RA-associated HVR3 cassettes (QKRAA, QRRAA) when expressed on a DR4 allele (P < 0.0001). In the prospective study, DR4-positive patients had a significantly increased risk (OR = 13.75, P = 0.00083) of developing bony erosions. In addition, HVR3 epitope-positive DR4-positive individuals had significantly higher Larsen indices than did epitope-negative patients (P = 0.0083). In particular, the presence of the HVR3 epitope on DR4 resulted in an increased a posteriori likelihood (0.91) of developing early erosive disease compared with an a priori risk of 0.62. Conversely, the likelihood decreased to a minimum of 0.35 when the HVR3 epitope was absent.

CONCLUSION

While the contribution of HLA typing to establishing the diagnosis of RA is limited, HLA-DR genotyping and DR4 subtype determination provide valuable markers for the prognosis of joint destruction in RA.

Increase of HLA-DRB1*0408 and -DQB1*0301 in HLA-B27 positive reactive arthritis

OBJECTIVE

To study HLA class II association in reactive arthritis.

METHODS

63 patients with reactive arthritis and 46 with rheumatoid arthritis were included in the study. HLA-DR alleles were determined by using a sequence specific PCR method. Oligonucleotide hybridisation was used for definition of DRB1*04 subtypes and DQB1 alleles. HLA-B27 was determined by standard microcytotoxity test or by PCR. HLA-B27 subtyping was made by sequencing.

RESULTS

46 (73%) of 63 patients with reactive arthritis were HLA-B27 positive and 24 (38%) were HLA-DRB1*04 positive. When haplotypes were inferred according to the known associations between DRB1 and DQB1 alleles, the frequency of DRB1*04-DQB1*0301 haplotype was found to be 13% (12/92) in HLA-B27 positive reactive arthritis patients, in contrast to 0% in HLA-B27 negative reactive arthritis (P = 0.04) and 1% in random controls (P = 0.0009). However, this combination was also found in 5% of 84 HLA-B27 positive control haplotypes, showing a linkage disequilibrium between B27 and this particular class II haplotype. HLA-DRB1*0408 subtype was found in 8/24 (33%) of the HLA-DRB1*04 alleles in patients with reactive arthritis, accounting for most DQB1*0301 haplotypes, but only in 5/55 (9%) of the DRB1*04 alleles in random controls (P = 0.017). All reactive arthritis patients with this subtype were positive for HLA-B27. DRB1*04-DQB1*0302 haplotype was increased in patients with rheumatoid arthritis (28/92, 30%) compared with reactive arthritis (12/126, 10%) or with the controls (12/100, 12%; P = 0.003). HLA-B*2705 was by far the dominant B27 subtype both in reactive arthritis patients with the particular DRB1*0408-DQB1*0301 haplotype and in controls. It was found in 11 out of 12 DR analysed patients, as well as in 10 out of 11 randomly selected B27 positive controls.

CONCLUSIONS

Although no single class II allele was found to be increased among patients with reactive arthritis, HLA-B27, DRB1*0408, and DQB1*0301 might exert a haplotypic effect in the pathogenesis of reactive arthritis, or they may be markers of a subset of B27 haplotypes conferring susceptibility.