Anti-Mouse CD137 (4-1BB) [Clone 3H3] — Purified in vivo PLATINUM™ Functional Grade

Clone 3H3 is primarily used as an agonistic monoclonal antibody targeting mouse CD137 (4-1BB), with several important in vivo applications in mouse research models.

Cancer Immunotherapy Studies

The predominant application of clone 3H3 is in cancer immunotherapy research. This antibody stimulates 4-1BB signaling to enhance anti-tumor immunity, particularly by activating CD8+ T cell responses. When administered in vivo, 3H3 has been shown to delay tumor growth in mouse models. The mechanism involves inducing more effector molecules from CD8+ T cells, increasing their proliferation, and decreasing apoptosis, all of which contribute to a more robust anti-tumor immune response.

Immune Modulation Research

Beyond cancer models, clone 3H3 is widely used to investigate immune modulation in infectious disease models. The antibody works by providing costimulatory signals to both CD4 and CD8 T cells, boosting T cell proliferation, IL-2 secretion, survival, and cytolytic activity. This makes it valuable for studying how enhancing T cell responses can combat various pathogens.

T Cell Activation Studies

Researchers utilize 3H3 to study T cell-mediated immune responses more broadly. The antibody's agonistic properties make it an effective tool for investigating how 4-1BB costimulation regulates CD28 co-stimulation in targeted cell subsets and favors Th1 development while maintaining long-term cell growth. It also helps researchers understand the duration and immunogenicity of dendritic cell-T cell interactions.

The antibody is typically administered at doses determined by individual research protocols, with functional grade preparations containing endotoxin levels ≤1.0 EU/mg to ensure minimal confounding effects in in vivo experiments.

Commonly used antibodies and proteins studied alongside 3H3 (an agonistic anti-4-1BB/CD137 antibody) in the literature include:

• Other anti-4-1BB antibodies: LOB12.3 and CTX-471-AF are frequently compared with 3H3 to evaluate differences in agonistic strength and mechanism.
• Immune checkpoint inhibitors: Antibodies against PD-1, PD-L1, and CTLA-4 are regularly used in combination with 3H3 to explore co-stimulatory and checkpoint pathways, particularly in cancer immunotherapy contexts.
• Other co-stimulatory antibodies: Anti-OX40 and anti-GITR are used in combinatorial studies to dissect synergistic effects in T cell activation and anti-tumor immunity.
• Cytokines: IL-2 and IL-15 are sometimes studied in combination with 3H3 to further enhance T-cell responses.
• Markers for immune cell subsets: Flow cytometry panels with antibodies against CD3ε, CD4, CD8β, CD25, NK1.1, IFN-γ, CD44, CD49b, CD62L, CD11c, Gr-1, and others are routinely used to profile immune responses to 3H3 treatment.
• Antibodies for checkpoint/activation markers: Anti-TIGIT and anti-Galectin-9 (Gal-9) are used when investigating mechanisms of T-cell exhaustion, activation, and immune regulation in the context of 3H3-based interventions.
• Fc receptor (FcγR)-related proteins and engineered cell lines: To distinguish the requirement for crosslinking in different agonistic antibodies including 3H3.

In summary, combinatorial approaches with 3H3 in the literature frequently include:

• Other anti-4-1BB antibodies (LOB12.3, CTX-471-AF)
• Immune checkpoint inhibitors (anti-PD-1, anti-PD-L1, anti-CTLA-4)
• Co-stimulatory pathway antibodies (anti-OX40, anti-GITR)
• Cytokines (IL-2, IL-15)
• Immune cell and functional markers (CD3, CD4, CD8, IFN-γ, Gal-9, TIGIT, etc.).

These combinations reflect ongoing efforts to maximize immunotherapeutic efficacy and dissect immune-modulating mechanisms in preclinical models.

Clone 3H3 is most frequently cited as a rat monoclonal antibody that acts as a strong agonist for mouse CD137 (4-1BB), a costimulatory receptor important for T-cell activation in immunotherapy, especially in cancer contexts. Key scientific findings from literature citing clone 3H3 include:

• Potent T-cell Activation and Tumor Infiltration: Clone 3H3 induces a robust and sustained increase in T-cell proliferation and infiltration within tumors, with notably higher activation compared to other CD137 agonist antibodies. This broad activation extends to both peripheral and intra-tumoral immune compartments, including significant expansion of cytotoxic (CD8+) T cells in the liver and spleen.

• Immunotherapy Efficacy and Toxicity: While 3H3 displays strong anti-tumor activity in preclinical models, it is often associated with wider immune activation, including increased levels of PD1+TIGIT+ T cells (markers of T cell exhaustion/activation) and induction of hepatic inflammation. These effects distinguish it from newer anti-4-1BB antibodies that aim to limit off-tumor toxicity.

• Fc Domain and Isotype Effects: The activity and safety profile of 3H3 is influenced by its rat IgG2a isotype, which in mice shows reduced ability to mediate antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis compared to human IgG4, but still effectively triggers receptor clustering and T cell co-stimulation. Comparisons highlight the importance of Fc/isotype selection in designing anti-4-1BB immunotherapies.

• Experimental Standard in Mouse Models: 3H3 is widely used as a benchmark antibody for preclinical evaluation of CD137/4-1BB–targeted therapies, immune activation, and anti-tumor efficacy in murine systems.

Other Contexts:
The search results also reference other "3H3" clones unrelated to immunology (such as anti-H3.3 histone antibodies and an amyloid-binding antibody disrupting Salmonella biofilms), but these are distinct reagents and not related to anti-CD137/4-1BB clone 3H3.

Summary Table: Clone 3H3 (anti-4-1BB/CD137) Key Findings

For most immunology and cancer biology citations, clone 3H3 refers specifically to the anti-mouse CD137 (4-1BB) antibody with the properties summarized above.

Dosing regimens of clone 3H3, an agonistic anti-mouse CD137 antibody, vary across mouse models depending on tumor type, mouse strain, and the isotype used, typically ranging from 100–300 μg per mouse per dose, often administered intraperitoneally every 3–7 days.

• Mouse Strain and Tumor Model Dependence: Most studies use immunocompetent strains such as C57BL/6 or BALB/c bearing subcutaneous tumors. The strain may influence pharmacokinetics and liver toxicity outcomes.

• Isotype Variation: 3H3 is available in multiple isotype forms (e.g., rat IgG2a, mouse IgG1, mouse IgG2a), each influencing efficacy and liver toxicity. For example, mouse IgG1 tends to produce less liver toxicity than mouse IgG2a due to differential Fcγ receptor binding. Modified isotypes (e.g., DANA mutants) with reduced FcγR binding can exacerbate liver toxicity, indicating the importance of Fc interaction.

• Dose and Frequency:

  • A typical regimen is 100–300 μg per mouse per injection, delivered via intraperitoneal route.
  • Dosing frequency ranges from every 3 days to once weekly for 2–4 weeks, depending on desired immune activation and study duration.

• Application Context: In tumor immunotherapy models, 3H3 is dosed to maximize peripheral immune activation without exceeding toxicity thresholds. Peripheral expansion of CD8⁺ T cells and upregulation of activation markers like PD1 and TIGIT are common endpoints; the dose may be lowered if adverse effects (e.g., liver enzyme elevations) are observed, which can be more pronounced with higher doses or specific isotypes.

• Special Mouse Models: Enhanced liver toxicity from 3H3 is observed in knockout models lacking specific Fcγ receptors (e.g., Fcgr3^−/−^, Fcer1g^−/−^), affecting ALT levels. This has led to the use of modified isotypes with lower activating/inhibitory FcγR binding ratios to fine-tune immune responses and toxicity.

Summary Table: Dosing of Clone 3H3 in Mouse Models

• Key insight: The dosing regimen is adjusted in response to observed toxicity and peripheral immune activation, with isotype selection and mouse genetic background being the major variables that dictate protocol optimization in different models.

If you need details for a specific mouse strain, tumor type, or dosing schedule, please specify for a targeted summary.