RAG2 Antibody

What is RAG2 and what is its role in the immune system?

RAG2 (recombination activating gene 2) is a critical protein involved in V(D)J recombination, which is essential for the development of B and T lymphocytes. The RAG complex (consisting of RAG1 and RAG2) facilitates the rearrangement of variable (V), diversity (D), and joining (J) gene segments during the development of B and T cell receptors, enabling the generation of diverse antibody and T cell receptor repertoires.

RAG2 is specifically expressed in cells of the B- and T-lymphocyte lineages . Defects in RAG2 can lead to various immunodeficiency disorders, including:

• Combined cellular and humoral immune defects with granulomas (CHIDG)

• Severe combined immunodeficiency (SCID) (T-B-NK+ form)

• Omenn syndrome (OS)

• Common variable immunodeficiency (CVID)

• Late-onset combined immunodeficiency (CID)

What applications are RAG2 antibodies typically used for in research?

RAG2 antibodies are versatile tools in immunology research with multiple applications. Based on the available data, the primary applications include:

These applications enable researchers to:

• Detect and quantify RAG2 protein expression levels in different cell types

• Study RAG2 localization within cells

• Assess RAG2 expression in tissue samples

• Isolate RAG2 protein complexes for interaction studies

For optimal results, titration of the antibody is recommended for each specific testing system, as sensitivity may vary between different experimental conditions and sample types .

How do researchers validate RAG2 antibody specificity?

Validating antibody specificity is crucial for reliable research results. For RAG2 antibodies, several validation approaches are commonly used:

• Western blot analysis with positive and negative controls:

  • Positive controls: Tissues or cell lines known to express RAG2 (e.g., thymus tissue, A375 cells)

  • Negative controls: Tissues or cell lines with no or minimal RAG2 expression

  • RAG2 knockout models: Comparing wildtype vs. RAG2-/- samples

• Molecular weight verification:

  • RAG2 is observed at 57-62 kDa on Western blots

  • The calculated molecular weight based on amino acid sequence is 59 kDa (527 amino acids)

• Immunoprecipitation followed by mass spectrometry:

  • This confirms that the antibody is pulling down the correct protein

• Immunostaining pattern consistency:

  • Verification that staining patterns match expected cellular localization

  • For RAG2, expression should be primarily detected in lymphoid tissues and specifically in developing B and T cell populations

• Cross-reactivity testing:

  • Testing the antibody against human, mouse, and rat samples to confirm species reactivity

  • The RAG2 antibody (11825-1-AP) reacts with human, mouse, and rat samples

What cell types or tissues express RAG2?

RAG2 expression has a distinctive pattern in the body, primarily restricted to developing lymphocytes:

• Primary expression sites:

  • Cells of the B- and T-lymphocyte lineages

  • Thymus (particularly in cortical thymocytes)

  • Bone marrow (in developing B cells)

• Developmental stages:

  • Most abundant in CD4+CD8+ double-positive (DP) T cell precursors

  • Expression decreases following positive selection

  • In B cells, expressed at the pro-B and pre-B cell stages

• Expression in research models:

  • Mouse thymus tissue shows detectable levels by Western blot

  • A375 cells (human melanoma cell line) have been used as a positive control

  • HeLa cells have been used for immunofluorescence studies

• Absence or minimal expression:

  • Mature peripheral T and B cells

  • Non-lymphoid tissues

  • Natural killer (NK) cells

This restricted expression pattern makes RAG2 a useful marker for identifying specific stages of lymphocyte development.

How do hypomorphic RAG2 mutations affect B cell development and selection?

Hypomorphic RAG2 mutations, which partially reduce but don't eliminate RAG function, lead to complex alterations in B cell development and selection:

• B cell phenotypic changes:

  • Enrichment of IgM+IgD+CD27+ cells, representing marginal zone (MZ)-like B cells

  • Increased frequency of CD21low B cells

  • Elevated unswitched CD27+ B cells

• Selective expansion of self-reactive B cells:

  • Studies of siblings with identical RAG2 mutations found expansion of B cells utilizing the self-reactive unmutated VH4-34 receptor

  • This suggests that hypomorphic RAG deficiency can promote the expansion of potentially autoreactive B cells

• Antibody repertoire alterations:

  • Features of an autoreactive antibody repertoire

  • Presence of secreted autoantibodies, including:

    • Elevated polyreactive IgM autoantibodies against various autoantigens

    • IgG autoantibodies against type I interferons (IFN-α and IFN-ω)

    • Elevated 9G4+ IgM reactivity

• Clinical spectrum:

  • Despite identical mutations, affected siblings showed divergent phenotypes:

    • Combined immunodeficiency with early mortality

    • Late-onset CID with hyper-IgM phenotype

    • B cell lymphopenia in some cases

  • Interestingly, despite detectable autoantibodies, clinical autoimmunity was not observed

These findings suggest that while hypomorphic RAG2 deficiency can alter B cell selection and promote self-reactive B cell expansion, additional factors may be required for clinical autoimmunity to develop.

What are the technical considerations when using RAG2 antibodies for different applications?

Using RAG2 antibodies effectively requires specific technical considerations for each application:

• Western Blot (WB):

  • Recommended dilution: 1:200-1:1000

  • Expected molecular weight: 57-62 kDa

  • Positive controls: A375 cells, mouse thymus tissue

  • Sample preparation: Standard SDS-PAGE protocols work well, as demonstrated with A375 cells

• Immunohistochemistry (IHC):

  • Recommended dilution: 1:20-1:200

  • Antigen retrieval: Suggested with TE buffer pH 9.0 or alternatively citrate buffer pH 6.0

  • Validated in human lymphoma tissue

  • Background control: Include appropriate isotype controls to distinguish specific from non-specific staining

• Immunofluorescence (IF)/Immunocytochemistry (ICC):

  • Recommended dilution: 1:10-1:100

  • Validated in HeLa cells

  • Counterstaining: Nuclear counterstain recommended as RAG2 has nuclear localization in active lymphocytes

• Immunoprecipitation (IP):

  • Recommended amount: 0.5-4.0 μg antibody for 1.0-3.0 mg of total protein lysate

  • Validated in A375 cells

  • Controls: Include IgG control IP to identify non-specific binding

• General considerations across applications:

  • Species reactivity: Validated for human, mouse, and rat samples

  • Storage: Store at -20°C, stable for one year after shipment

  • Buffer composition: PBS with 0.02% sodium azide and 50% glycerol pH 7.3

  • Titration: Sample-dependent optimization recommended for optimal results

How can RAG2 antibodies be used to study V(D)J recombination defects?

RAG2 antibodies can be valuable tools for investigating V(D)J recombination defects through several research approaches:

• Detection of RAG2 protein expression in patient samples:

  • Western blot analysis can assess RAG2 protein levels in patient-derived lymphocytes

  • Reduced or absent protein may indicate pathogenic mutations affecting protein stability

• Characterization of RAG2 variant effects:

  • Comparing RAG2 protein levels between healthy controls and patients with suspected RAG2 deficiency

  • Immunoprecipitation followed by mass spectrometry can identify altered interaction partners

• T cell development assessment:

  • Immunostaining of thymic biopsies can reveal abnormal patterns of RAG2 expression

  • The loss of distal Vα7.2+ receptor expression on circulating T cells serves as a reliable biomarker for functionally testing recombination activity

• Functional studies in cellular models:

  • Using RAG2 antibodies to confirm successful gene editing in CRISPR-Cas9 modified cell lines

  • Validating RAG2 knockdown or knockout in experimental systems

• Analysis of recombination activity:

  • In vitro recombination assays with patient-derived RAG2 variants

  • Complementation of RAG2-deficient cells with wildtype or mutant RAG2, followed by antibody detection

From research findings, RAG2 deficiency leads to specific developmental blocks:

• Halt of conventional T cell development at the double-positive (DP) T precursor stage

• Prevention of positive selection

• Inability to perform V(D)J recombination, leading to absence of mature B and T cells

What is the relationship between RAG2 deficiency and autoimmunity?

The relationship between RAG2 deficiency and autoimmunity reveals a complex immunological paradox:

• Autoantibody production in RAG2 deficiency:

  • Siblings with hypomorphic RAG2 mutations show:

    • Elevated polyreactive IgM autoantibodies against various autoantigens

    • IgG autoantibodies against type I interferons (IFN-α and IFN-ω)

    • Elevated 9G4+ IgM reactivity (associated with self-reactivity)

• B cell repertoire alterations:

  • Expansion of self-reactive B cells utilizing unmutated VH4-34 receptor

  • Enrichment of marginal zone-like B cells (IgM+IgD+CD27+)

  • Increased frequency of CD21low B cells, which are associated with autoimmunity in other contexts

• Clinical-laboratory paradox:

  • Despite detectable autoantibodies, clinical autoimmunity was not observed in the studied siblings

  • "The presence of self-reactive IgM was not sufficient to mediate or trigger autoimmunity"

• Disease spectrum:

  • RAG2 mutations can cause a range of clinical manifestations including:

    • Combined cellular and humoral immune defects with granulomas (CHIDG)

    • Omenn syndrome (OS), characterized by oligoclonal T cells, hypereosinophilia, and high IgE

    • Severe combined immunodeficiency (SCID)

• Mechanistic insights:

  • Hypomorphic RAG2 deficiency may promote positive selection for self-reactivity during marginal zone B cell development

  • Environmental triggers or secondary genetic factors likely needed for clinical autoimmunity to develop

How do researchers use RAG2 knockout models in immunology research?

RAG2 knockout models serve as valuable tools in immunology research, enabling insights into lymphocyte development, immune system function, and disease mechanisms:

• T cell development studies:

  • RAG2 knockout PSCs (pluripotent stem cells) show halted T cell development at the double-positive (DP) T precursor stage

  • Prevention of positive selection, similar to findings in RAG-deficient patients

  • Research has demonstrated that T cell development from RAG-deficient PSCs arrests at the DP stage

• Generation of TCR-specific T cells:

  • RAG1−/−RAG2−/−B2M− human PSCs can be engineered to express a single TCR

  • This prevents TCR mispairing, resulting in T cells with better tumor control in mice compared to T cells with intact endogenous TCR

  • Overcomes challenges in developing T cell immunotherapies from allogeneic PSCs

• Immunodeficiency disease modeling:

  • RAG2 knockout models recapitulate features of severe combined immunodeficiency (SCID)

  • Used to study mechanisms of immune deficiency and test potential therapeutic interventions

• Reconstitution experiments:

  • RAG2-deficient animals lack mature B and T cells but retain normal NK cells (T-B-NK+ phenotype)

  • Serve as recipients for adoptive transfer studies to investigate cellular reconstitution

  • Used to test gene correction approaches for RAG deficiency treatment

• Control models in antibody validation:

  • RAG2 knockout tissues serve as negative controls for antibody specificity validation

  • Ensure that antibody staining is specific to the target protein

What methods are used to assess RAG2 recombination activity in clinical samples?

Assessing RAG2 recombination activity in clinical samples is crucial for diagnosing and characterizing RAG deficiency. Several complementary approaches are used:

• Biomarkers of recombination deficiency:

  • Loss of distal Vα7.2+ receptor expression on circulating T cells serves as a reliable biomarker for defective recombination activity

  • Research shows that PBMCs from affected siblings lacked detectable CD3+Vα7.2+ cells, while healthy siblings expressed normal percentages (2-9% Vα7.2+ of CD3+ cells)

• In vitro recombination assays:

  • Measurement of recombination efficiency using reporter constructs

  • Can detect hypomorphic activity, where some function is retained

  • Research indicates that "recombination activity is not the only phenotypic driver" of disease severity

• TCR and BCR repertoire analysis:

  • Next-generation sequencing to assess diversity and composition

  • Evaluation of CDR3 length distribution and V/D/J usage patterns

  • Can reveal skewing or oligoclonality characteristic of partial RAG deficiency

• Functional complementation studies:

  • Introduction of wild-type RAG2 into patient cells to rescue defects

  • Comparing activity of different RAG2 variants can assess residual function

  • Research cautions that "compound heterozygous RAG2 variants can manifest a recombination defect only detectable by assessment in the setting of broad RSS target sequences"

• Protein modeling and energetics calculation:

  • 3D variant models of RAG2 mutations (e.g., G243V and C423Y)

  • Created using computational tools like FoldX, followed by energetics calculation

  • Electrostatic visualization using tools such as APBS and PyMOL

How can RAG-deficient pluripotent stem cells be used in T cell development research?

RAG-deficient pluripotent stem cells (PSCs) have emerged as valuable tools for T cell development research and therapeutic applications:

• Generation of TCR-specific mature T cells:

  • RAG1−/−RAG2−/− B2M− human PSCs can be engineered to express a single TCR

  • This approach prevents TCR mispairing, which is a significant challenge in T cell therapy development

  • T cells generated this way showed "substantially better tumour control in mice than T cells with an intact endogenous TCR"

• T cell development pathway investigation:

  • RAG-deficient PSCs can be differentiated towards the T cell lineage using artificial thymic organoid (ATO) systems

  • This allows observation of developmental blockades at specific stages

  • Differentiation profile of RAG1/RAG2 double knockout (DKO) PSCs shows that deletion "halts conventional T cell development at the DP T precursor stage and prevents positive selection"

• Overcoming allogeneic T cell therapy challenges:

  • Introducing T cell selection components into the stromal microenvironment of PSCs "overcomes inherent biological challenges associated with the development of T cell immunotherapies from allogeneic PSCs"

  • This approach may improve efficacy and safety of PSC-derived T cell therapies

• Tracking developmental progression:

  • Similar developmental blocks are observed in RAG-deficient PSCs as in RAG-deficient patients

  • This parallelism validates the model for studying human RAG deficiency

• Therapeutic potential:

  • Engineering single TCR expression in RAG-deficient PSCs offers advantages for immunotherapy development

  • The absence of endogenous TCR rearrangements eliminates the risk of unexpected or self-reactive specificities