Anti-Mouse IFNAR-1 [Clone MAR1-5A3] — Purified in vivo GOLD™ Functional Grade

Clone MAR1-5A3 is used in in vivo mouse studies to functionally block type I interferon (IFN) receptor signaling by targeting the IFNAR-1 (interferon alpha/beta receptor subunit 1) on mouse cells without depleting the cells that express it.

Key details:

• Mechanism: MAR1-5A3 is a monoclonal antibody that binds specifically to mouse IFNAR-1, a key part of the heterodimeric type I IFN receptor complex (IFNAR-1/IFNAR-2). This prevents type I IFNs (IFN-? and IFN-?) from binding their receptor, thereby blocking downstream signaling and the induction of interferon-stimulated genes (ISGs).
• Typical use: It is administered to mice to create a transient and systemic blockade of type I IFN responses, allowing researchers to study the effects of type I IFN signaling deficiency in various physiological or disease models, such as viral infection, cancer, or autoimmune conditions.
• Administration and dosing: A loading dose is required to saturate all in vivo IFNAR1 binding sites, followed by maintenance dosing due to rapid receptor recycling; for example, studies mention 200?µg every three days or a protocol of 2.5?mg/mouse followed by 0.5?mg/mouse weekly.
• Non-depleting: MAR1-5A3 blocks receptor function without causing cell depletion because it is typically used as mouse IgG1, which, unlike other isotypes, does not mediate antibody-dependent cellular cytotoxicity or complement activation.

Summary of applications:

• Used to mimic a type I IFN receptor knockout in wild-type mice.
• Investigates the role of type I IFN signaling in immune response, pathogen defense, tumor immunity, and autoimmunity.
• Often preferred for temporal and reversible abrogation versus permanent gene deletion.

Special notes:

• Recombinant versions (e.g., MAR1-5A3-CP056) have been engineered (IgG2a isotype, Fc silenced) to further reduce any potential for effector functions, paralleling therapeutic anti-IFNAR1 antibodies.
• The antibody requires regular dosing because of the turnover and recycling of IFNAR-expressing cells; this ensures consistent blockade.

Commonly used antibodies and proteins in the literature alongside MAR1-5A3 include other monoclonal antibodies targeted at interferon signaling components, isotype controls, and antibodies against viral or cellular proteins relevant to the specific experimental context.

Key examples include:

• Isotype controls: Frequently used are IgG2a mAb (2H2) against dengue virus prM protein, GIR-208, and PIP as controls to MAR1-5A3, ensuring experimental specificity.
• Other interferon pathway antibodies: TIF-3C5 and HDβ-4A7 are cited as antibodies blocking or detecting interferon alpha or beta, used in experiments to compare with or complement MAR1-5A3's effects.
• Related receptor antibodies: Since IFNAR-1 and IFNAR-2 form a heterodimeric receptor complex, studies may also utilize antibodies targeting IFNAR-2 to explore the full signaling blockade.
• Cellular marker antibodies: Depending on the study focus (e.g., immunophenotyping after IFNAR blockade), antibodies against immune cell surface markers (CD3, CD4, CD8, CD45, etc.) are often used together for flow cytometry or functional assays.
• Other cytokine or viral protein antibodies: In viral infection models, coworkers such as anti-dengue virus prM protein are used for viral detection or quantification.

Additional details:

• MAR1-5A3 is commonly paired with isotype controls in blocking or depletion experiments for unbiased functional assessment.
• Recombinant or chimeric forms of MAR1-5A3 (e.g., MAR1-5A3-CP056) are available to enable specific functional studies with modified Fc regions for decreased effector functions (preventing ADCC/CDC), which may be co-used with other immune-modulatory antibodies.

In summary, MAR1-5A3 is typically used alongside control antibodies, complementary interferon-targeting clones (such as anti-IFN-?), and standard immunological markers, all tailored to the experimental design and hypothesis.

The monoclonal antibody clone MAR1-5A3 is widely cited in scientific literature for its role as a blocking antibody against mouse type I interferon receptor (IFNAR1), enabling experimental manipulation of interferon signaling in vivo. Key findings from studies citing MAR1-5A3 cover its central use in dissecting the immune response, developing infection models, and understanding pathogenesis mechanisms.

Key findings:

• Mechanism and Specificity: MAR1-5A3 binds to the extracellular domain of mouse IFNAR1, blocking type I interferon (IFN-α/β) signaling, which is central to innate antiviral, antimicrobial, antitumor, and autoimmune responses.

• Immune Modulation: Blocking IFNAR1 with MAR1-5A3 enhances certain aspects of humoral immunity. In particular, it increases the generation of T follicular helper (T_FH) cells, germinal center (GC) B cells, and plasma cells during chronic viral infection (e.g., lymphocytic choriomeningitis virus, LCMV). This blockade results in higher virus-specific antibody levels, demonstrating that type I IFN signaling restrains aspects of the antiviral humoral response.

• Infection Models and Disease Susceptibility: MAR1-5A3 is crucial for creating mouse models permissive to flavivirus infection (e.g., Zika virus, West Nile virus, Usutu virus, dengue virus) in otherwise resistant wild-type mice. Key findings here:

  • Pre-treatment with MAR1-5A3 leads to enhanced viral replication, increased viremia, and in some cases, lethal disease, mimicking immunodeficient mouse phenotypes.
  • The route, dose, and timing of antibody administration can modulate disease severity.
  • Pathogenic outcomes depend on factors such as viral strain, dose, mouse age, and route of inoculation.
  • MAR1-5A3 does not efficiently cross the blood brain barrier, so observed neurovirulence after infection is likely due to enhanced systemic infection and CNS invasion by the virus.

• Technical Considerations: MAR1-5A3 administration is transient, non-cell-depleting, and has a defined half-life (around 5.2 days in wild-type mice), influencing experimental design and virus kinetics in mouse models.

These findings establish MAR1-5A3 as a powerful tool for:

• Temporarily disabling type I IFN signaling in vivo without genetic knockouts.
• Dissecting how type I IFN pathways shape immune responses to infection, vaccination, and tumor immunity.
• Facilitating modeling of severe viral diseases and vaccine evaluation, especially for viruses poorly infectious in immunocompetent mice.

Most studies agree on these findings, although specific pathogenic outcomes and immunological consequences may vary depending on experimental context and viral factors.