CAT #: 91010020
IdentiClone® IGH Gene Clonality Assay - Gel Detection
The IdentiClone® IGH Gene Clonality Assay is an in vitro diagnostic product intended for PCR-based detection of clonal immunoglobulin heavy chain gene rearrangements in patients with suspect lymphoproliferations.
Specifically, the IGH Gene Clonality Assay can be used to:
- Identify clonality in atypical lymphoproliferative disorders
- Support a differential diagnosis between reactive lesions and hematologic malignancies
- Assign presumptive lineage in mature monoclonal lymphoproliferative disorders
- Identify tumor-specific markers (IGH gene rearrangements) for post-treatment monitoring
- Monitor and evaluate disease recurrence
- Summary of Explanation of the Test
Rearrangements of the antigen receptor genes occur during ontogeny in B and T lymphocytes. These gene rearrangements generate products that are unique in length and sequence for each cell. Therefore, polymerase chain reaction (PCR) assays can be used to identify lymphocyte populations derived from a single cell by detecting the unique V-J gene rearrangements present within these antigen receptor loci. This IdentiClone® PCR assay employs multiple consensus DNA primers that target conserved genetic regions within the immunoglobulin heavy chain gene. This test is used to detect the vast majority of clonal B-cell malignancies from DNA. Test products can be analyzed using a variety of detection formats, including gel and capillary electrophoresis.
Gene rearrangement analysis can also be performed by Southern Blot (SB)-based techniques. Although SB analysis is very reliable, it is increasingly replaced by PCR techniques because of the greater efficiency and sensitivity of PCR. Moreover, PCR is relatively easy, less labor intensive, and requires much lower quantities of high molecular weight DNA than SB tests. In addition, PCR can often be performed on DNA isolated from paraffin-embedded tissue, whereas SB cannot be performed because the DNA is often degraded. Therefore, there is a strong need to replace SB analysis with reliable PCR techniques.
Invivoscribe’s IdentiClone® assays represent a new approach to PCR-based clonality testing. These standardized assays were carefully optimized testing positive and negative control samples using multiplex master mixes. Assay development was followed by extensive validation including the testing of more than 400 clinical samples using Revised European/American Lymphoma (REAL) Classification. Testing was done at more than thirty prominent independent testing centers throughout Europe in a collaborative study known as the BIOMED-2 Concerted Action. Results from this BIOMED-2 study appear in Leukemia, a leading peer-reviewed journal.
The gel detection based assays cannot reliably detect clonal populations comprising less than 5% of the total lymphocyte cell population. It should be emphasized that the results of molecular clonality tests should always be interpreted in the context of clinical, histological and immunophenotypic data.
This test kit includes 6 master mixes. The IGH Tube A, B, and C master mixes target the framework 1, 2, and 3 regions (respectively) within the variable region, and the joining region of the immunoglobulin heavy chain locus. The IGH Tube D and E master mixes target the diversity and joining regions. Lastly, the Specimen Control Size Ladder master mix, targets multiple genes and generates a series of amplicons of approximately 100, 200, 300, 400, and 600 basepairs to ensure that the quality and quantity of input DNA is adequate to yield a valid result. A single thermocycler program and similar detection methodologies are used with all of our Gene Clonality Assays. This improves consistency and facilitates cross training on a broad range of different assays.
- Principles of the Procedure
Polymerase Chain Reaction (PCR)
PCR assays are routinely used for the identification of clonal B-cell populations. These tests amplify the DNA between primers that target the conserved framework (FR) of the variable (V) regions and the conserved joining (J) regions (IGH Tube A-C), as well as the diversity (D) and joining regions (IGH Tube D & E). These conserved regions lie on either side of an area within the V-J region where programmed genetic rearrangements occur during maturation of all B and T lymphocytes. The antigen receptor genes that undergo rearrangement are the immunoglobulin heavy chain andlight chains in B-cells, and the T cell receptor genes in T-cells. Each B- and T-cell has a single productive V-J rearrangement that is unique in both length and sequence. Therefore, when DNA from a normal or polyclonal population is amplified using DNA primers that flank the V-J region, a bell-shaped curve (Gaussian distribution) of amplicon products within an expected size range is produced. This Gaussian distribution reflects the heterogeneous population of V-J rearrangements. (In certain cases, where lymphocyte DNA is not present, no product is seen.) For DNA from samples containing a clonal population, the yield is one or two prominent amplified products (amplicons) within a diminished polyclonal background.
Since the antigen receptor genes are polymorphic (consisting of a heterogeneous population of related DNA sequences), it is difficult to employ a single set of DNA primer sequences to target all of the conserved flanking regions around the V-J rearrangement. N-region diversity and somatic mutation further scramble the DNA sequences in these regions. Therefore multiplex master mixes, which target several FR regions, are required to identify the majority of clonal rearrangements. As indicated, clonal rearrangements are identified as prominent, single-sized products within the background of different-sized amplicon products that form a Gaussian distribution around a statistically favored, average-sized rearrangement. Note that the primers that amplify the different FR regions, which are located at three distinct sections along the heavy chain gene, produce a correspondingly different size-range of V-J products.
Gel electrophoresis, such as agarose gel electrophoresis or non-denaturing polyacrylamide gel electrophoresisis (PAGE), is commonly used to resolve the different amplicon products based on their size, charge, and conformation. Since DNA is negatively charged, when an electrical potential (voltage) is applied across the gel containing PCR products, the electrical field causes the amplicons to migrate through the gel. Smaller DNA fragments are able to easily migrate through the gel matrix, whereas larger DNA fragments migrate more slowly. This causes a separation of the amplicon products based on size. Ethidium bromide or other DNA intercalating dyes can then be used to stain and detect these products in the gel.
A heteroduplex analysis can also be performed and run on a polyacrylamide gel to differentiate clonal and non-clonal PCR products. A heteroduplex analysis involves denaturing the PCR products at a high temperature, then quickly re-annealing the DNA strands by suddenly reducing the temperature. This causes a large portion of DNA strands to incorrectly bind to other non-homologous strands creating loops in the DNA. These loops cause a significant reduction in the ability of the DNA to migrate through a polyacrylamide gel. However, if the majority of the PCR products are clonal, when a heteroduplex analysis is performed, most of these PCR products will correctly re-anneal with a homologous strand. These PCR products will run normally through the polyacrylamide gel. Therefore, in a clonal sample with a polyclonal background, a heteroduplex analysis will cause most of the polyclonal product to run much slower through the polyacrylamide gel, thereby increasing their separation and the ability to identify the clonal band(s).
- Specimen Requirements
This assay tests genomic DNA from the following sources:
- 5cc of peripheral blood, bone marrow biopsy, or bone marrow aspirate anti-coagulated with heparin or EDTA (stored at 2°C to 8°C and shipped at ambient temperature)
- Minimum 5mm cube of tissue (stored and shipped frozen; or stored and shipped in RPMI 1640 at ambient temperature or on ice)
- 2µg of genomic DNA (stored at 2°C to 8°C and shipped at ambient temperature)
- Formalin-fixed paraffin embedded tissue or slides (stored and shipped at ambient temperature)
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CE-marked IVD products are intended for in vitro diagnostic use. Not available in North America.
This assay is based on the EuroClonality/BIOMED-2 Concerted Action BMH4-CT98-3936.
Use of this product may require nucleic acid amplification methods such as Polymerase Chain Reaction (PCR). No patent license to use amplification processes or enzymes is conveyed expressly or by implication to the purchaser by the purchase of these products.
Purchase of this product includes a limited sublicense for non-commercial uncompensated practice of this technology if and only if the purchaser is registered with IVS as an exclusively non-commercial user of IVS products. No sublicense for such use is granted simply by purchase of these products. To request a form for registration as an exclusively non-commercial product user, to discuss terms for a potential sublicense for broader practice of these methods, or for other questions please contact IVS by email at firstname.lastname@example.org, or by telephone at +1 858 224 6600.
IdentiClone® is a trademark of Invivoscribe, Inc