Routine HLA-B27 typing by flow cytometry: differentiation of the products of HLA-B*2702, B*2705 and B*2708

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.

Human HLA-B27 typing using the BD™ HLA-B27 kit on the BD FACSVia™ system: A multicenter study

The BD FACSVia™ system is a novel flow cytometer with improved workflow efficiencies. To evaluate the HLA‐B27 application developed on the BD FACSVia system utilizing the BD™ HLA‐B27 kit, we conducted a concordance study at three centers to compare with the BD FACSCalibur™ system. Prepared donor samples (n = 594) were analyzed on both the BD FACSVia and BD FACSCalibur for the HLA‐B27 assay. Adjudication of HLA‐B27 discordant results was performed using the reverse sequence‐specific oligonucleotide (rSSO) DNA typing method (LABType® SSO, One Lambda). On the BD FACSVia system 80 B27 positive, 499 B27 negative and 15 “Inconclusive” samples were observed. The corresponding BD FACSCalibur results were 73 B27 positive, 502 B27 negative and 19 “gray zone” samples. The overall concordance of HLA‐B27 determination was 98% between the two systems with seven more positives identified on BD FACSVia as compared to BD FACSCalibur. The equivocal zone between positive and negative on BD FACSVia (named “Inconclusive”) and on BD FACSCalibur (named “gray zone”) is due to antibody cross reactivity of HLA‐B27 clone GS145.2. One negative sample verified with the rSSO DNA method was reported as HLA‐B27 positive by the BD FACSVia system leading to a false positive result. Our study demonstrated concordance results between the BD FACSVia system and BD FACSCalibur. Intersite reproducibility of BD HLA‐B27 assay remained within the limits of acceptability. © 2018 The Authors. Cytometry Part B: Clinical Cytometry published by Wiley Periodicals, Inc. on behalf of International Clinical Cytometry Society

Flow cytometric human leukocyte antigen-B27 typing with stored samples for batch testing

Background

Flow cytometry (FC) HLA-B27 typing is still used extensively for the diagnosis of spondyloarthropathies. If patient blood samples are stored for a prolonged duration, this testing can be performed in a batch manner, and in-house cellular controls could easily be procured. In this study, we investigated various methods of storing patient blood samples.

Methods

We compared four storage methods: three methods of analyzing lymphocytes (whole blood stored at room temperature, frozen mononuclear cells, and frozen white blood cells [WBCs] after lysing red blood cells [RBCs]), and one method using frozen platelets (FPLT). We used three ratios associated with mean fluorescence intensities (MFI) for HLAB27 assignment: the B27 MFI ratio (sample/control) for HLA-B27 fluorescein-5-isothiocyanate (FITC); the B7 MFI ratio for HLA-B7 phycoerythrin (PE); and the ratio of these two ratios, B7/B27 ratio.

Results

Comparing the B27 MFI ratios of each storage method for the HLA-B27+ samples and the B7/B27 ratios for the HLA-B7+ samples revealed that FPLT was the best of the four methods. FPLT had a sensitivity of 100% and a specificity of 99.3% for HLA-B27 assignment in DNA-typed samples (N=164) when the two criteria, namely, B27 MFI ratio >4.0 and B7/B27 ratio <1.5, were used.

Conclusions

The FPLT method was found to offer a simple, economical, and accurate method of FC HLA-B27 typing by using stored patient samples. If stored samples are used, this method has the potential to replace the standard FC typing method when used in combination with a complementary DNA-based method.

Comprehensive evaluation of two HLA-B17 monoclonal antibodies for flow cytometry-based HLA-B57/B58 screening prior to abacavir prescription

Hypersensitivity reactions to the drug abacavir, used to treat HIV/AIDS patients, is associated with possession of HLA-B*57:01. We have carefully assessed two commercially available HLA-B57/B58 murine monoclonal antibodies [0196HA and BIH0243 (One Lambda Inc.)] in a simple flow cytometry-based assay. The evaluation involved tests on 228 reference and random samples covering 91% of all WHO recognized HLA-A, B and C specificities. These involved donors with six different HLA-B*57 alleles and included 19 examples of B*57:01. Both antibodies unambiguously detected B57, but there were small difference in their reactivity against B57-positive non-B*57:01 samples. Importantly, there was no reactivity against B57/B58-negative samples. The possible amino acid motifs involved in the reactivity of these antibodies with B57/B58 were delineated. Thus, HLA-B57/B58, normally present in <10% of patients, can be easily recognized using these two antibodies and further tested by a DNA-based typing method to identify B*57:01.

One-tube HLA-B27/B2708 typing by flow cytometry using two "Anti-HLA-B27" monoclonal antibody reagents

BACKGROUND

Flow cytometry-based methods are widely used to detect the ankylosing spondylitis-associated HLA-B27/B2708 antigens. However, the generally used "HLA-B27" monoclonal antibodies (moabs) cross-react with many HLA specificities, including the common HLA-B7 antigen. Thus, using two "B27" moabs is highly recommended.

METHODS

The assay used two "HLA-B27" reagents, FITC and PE conjugated, respectively and a PE-Cy5 anti-CD3 antibody. Assay verification used 51 reference subjects possessing B*2705, B*2702, and B*2708 and a range of cross-reactive HLA antigens. A total of 1,006 consecutive patients' samples, referred for "HLA-B27 typing", were assayed alongside our standard flow cytometry method. A further 12 low frequency HLA-B*27 specificities were tested. Samples reacting with one "B27" moab only were B*27 allele typed by PCR using sequence-specific primers.

RESULTS

All patient B27/B2708 positives (28.3%) were identified by our one-tube method which detected B*2705, B*2702, B*2708, and 8/12 other B*27 specificities. It was unaffected by HLA-B7 and other cross-reactive antigens but required a minor adjustment, a reduction in the volume of one of the "B27" moabs used, to avoid detecting a minority of HLA-B57 subjects.

CONCLUSIONS

Our one-tube B27/B2708 assay is simple, robust, uses two "B27" moabs for typing precision and security, does not suffer from interference by HLA-B7 or other cross-reactive antigens and has the obvious advantage of using a single tube per typing.

Application of the particle gel agglutination assay in the typing of single human leucocyte antigens

We describe a simple and rapid particle gel agglutination assay (PaGIA) for typing of the human leucocyte antigens (HLA) HLA-A2, HLA-B7 and HLA-B27. Superparamagnetic streptavidin particles were coated with biotinylated monoclonal antibodies (MoAbs) to HLA-A2, HLA-B7 and HLA-B27. Anticoagulated whole blood samples from healthy blood donors (n = 118) with known HLA patterns were incubated with MoAb-coated particles, transferred into a standard ID-gel card, and subsequently centrifuged. Samples were evaluated macroscopically, with antigen-positive samples resulting in a visible agglutination reaction. A clear distinction could be made between all positive and negative samples tested. Fifty-seven samples were found to be positive for HLA-A2 (48%), 26 samples for HLA-B7 (22%) and 5 samples for HLA-B27 (4%).

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.

A high-resolution polymerase chain reaction-sequence-specific primer HLA-B*27 typing set and its application in routine HLA-B27 testing

We designed a set of 35 polymerase chain reaction sequence-specific primers (PCR-SSP) in 29 SSP mixtures to assign 29 HLA-B*27 4-digit level alleles (B*2701-B*2721 and B*2723-B*2730). This was used in conjunction with our 41 PCR-SSP primer mixture low-resolution HLA-B typing set to fully differentiate B*27 from all other HLA-B alleles. Successful typing set validation used 521 B*27 samples covering 13 (B*2701-B*2710 and B*2712, B*2717, B*2723) alleles. The distribution of B*27 alleles was determined in a random population of 4020 local blood donors and the use of PCR-SSP B*27 typing in our routine flow cytometry-based HLA-B27/B2708 typing strategy is described.

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.

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.

An evaluation of Com-B27, a fluorescein-conjugated mouse anti-HLA-B27 reagent

We evaluated the HLA-B27 typing reagent Com-B27, which is claimed to show minimal cross-reactivity with HLA-B7, for use in flow cytometry-based typing. This combination reagent consists of the fluorescein-conjugated HLA-B27 mouse monoclonal antibody ABC-m3 and a non-conjugated HLA-B7 monoclonal antibody that is claimed to block the reactivity of ABC-m3 to B7 without affecting its reactivity to B27. It reacted well with B27 (B*2702, B*2705) and B2708 [mean median channel fluorescence intensity (MCFI) 8.40] and weakly with B7 (including cells from homozygous B*07 donors), B42/B73 and B22/B37/B44 reference cells (mean MCFI 2.05, 3.09 and 1.10, respectively). It showed a uniform discrimination between B7 and B27/B2708 with no 'overlap' in MCFI values, which was seen with the standard ABC-m3 antibody. There was complete agreement when our standard three-antibody-based B27/B2708 flow cytometry assay and the Com-B27 reagent alone were used to independently assign B27/B2708 status to 651 random patients. Thus, the Com-B27 reagent provided improved discrimination between B7 and B27/B2708 over the ABC-m3 antibody, and its B27/B2708 assignments were comparable with our standard flow cytometry assay. However, for consistently reliable B27/B2708 typing we continue to recommend the use of a minimum of two B27 reagents in a protocol that includes DNA-based testing of 'equivocal' B27/B2708 assignments.

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.

HLA-B27 expression by flow cytometry: an analysis of 7 years quality assurance data

The Royal College of Pathologists of Australasia Quality Assurance Programs Pty. Ltd. has been monitoring HLA-B27 assignment by flow cytometry for 7 years as part of the Immunology Program. Here we present data that demonstrates a gradual improvement in reports of false positive and negative results. Many participating laboratories demonstrate an ability to assign HLA-B27 status correctly by flow cytometric means. This ability appears to be independent of reagent and methodology. However a small number of laboratories produce consistently unacceptable results that suggest poor quality assurance practice.

The application of flow cytometry to histocompatibility testing

Flow cytometry is a powerful technique that enables the sensitive and quantitative detection of both cellular antigens and bound biological moieties. This article reviews how flow cytometry is increasingly being used as histocompatibility laboratories for the analysis of antibody specificity and HLA antigen expression. A basic description of flow cytometry principles and standardisation is given, together with an outline of clinical application in the areas of pre-transplant cross-matching, antibody screening, post-transplant antibody monitoring and HLA-B27 detection. It is concluded that flow cytometry is a useful multi-parametric analytical tool, yielding clinical benefit especially in the identification of patients at risk of early transplant rejection.