Mouse IgG_2a Isotype Control [Clone C1.18.4] — Purified in vivo GOLD™ Functional Grade

Clone C1.18.4 is a mouse IgG2a isotype control antibody that serves as a negative control in various in vivo mouse studies rather than targeting specific antigens. Its primary function is to account for non-specific binding and background effects in experimental settings where antigen-specific mouse IgG2a antibodies are being tested.

Primary Role in In Vivo Research

The C1.18.4 clone functions as an isotype-matched negative control to distinguish specific biological effects from non-specific antibody interactions. This antibody has been specifically tested against mouse cells and tissues to ensure minimal cross-reactivity, making it particularly suitable for in vivo mouse experiments.

Common Experimental Applications

In mouse studies, C1.18.4 is used to control for potential confounding factors including:

• Fc receptor-mediated effects: Non-specific binding to Fc receptors on immune cells
• Complement activation: Background immune system activation unrelated to the target antigen
• General antibody administration effects: Physiological responses to antibody injection itself

Researchers typically administer C1.18.4 alongside the test antibody to separate target-specific effects from these non-specific responses.

Technical Specifications for In Vivo Use

The clone is manufactured to meet stringent requirements for in vivo applications, including low endotoxin levels (less than 1.0 EU/mg or even below 0.5 EU/mg for ultra-low endotoxin versions). The antibody achieves high purity (>95%) through protein A or G affinity chromatography and undergoes 0.2 µm filtration for sterility. These specifications are critical for minimizing inflammatory responses and other artifacts in living animals.

Fc-Modified Variants

A specialized version of C1.18.4 with LALA-PG mutations is available for experiments requiring Fc silencing. This Fc-muted variant eliminates effector functions while maintaining the isotype control properties, useful when researchers need to isolate antigen-binding effects from Fc-mediated immune responses.

Commonly Used Antibodies and Proteins Alongside C1.18.4

C1.18.4 is a well-characterized mouse monoclonal antibody of the IgG2a, kappa isotype, used almost exclusively as a negative (isotype-matched) control in immunological and cell biology experiments. Its primary function is to provide a benchmark for non-specific binding and background signal when evaluating antigen-specific antibodies of the same isotype.

Typical Experimental Pairings

• Antigen-Specific Mouse IgG2a Antibodies: C1.18.4 is most often paired with other mouse IgG2a antibodies targeting specific cell surface markers or antigens. For example, in the context of murine MHC class I studies, C1.18.4 is used alongside antibodies such as 34-1-2S, SF1.1.10, and AF6-88.5, which are specific for different MHC class I alleles (e.g., H-2Kd, H-2Kb). This allows researchers to distinguish specific antigen binding from non-specific background.
• Other Isotype Controls: In multiplexed experiments, C1.18.4 may also be used together with isotype controls for other mouse antibody subclasses (e.g., IgG1, IgG2b) to control for subclass-specific effects across multiple markers.
• Experimental Systems: While C1.18.4 itself has no known antigen specificity, it is frequently employed in both in vitro assays (e.g., flow cytometry, immunohistochemistry) and in vivo mouse models to validate the specificity of experimental antibodies.

Example Applications in the Literature

• Flow Cytometry and Immunohistochemistry: C1.18.4 is included as an isotype control whenever mouse IgG2a primary antibodies are used to detect specific targets, ensuring that observed signals are due to specific antigen-antibody interactions rather than non-specific Fc receptor binding.
• In Vivo Studies: In animal experiments, C1.18.4 serves as a negative control for antibody therapeutics or probes, helping to rule out artifact or toxicity due to the antibody isotype itself.
• Complement Studies: Although not a common use case, some complement activation studies may include C1.18.4 as a control alongside complement-activating IgG2a antibodies (e.g., 34-1-2S), but C1.18.4 itself does not activate complement.

Summary Table: Typical Antibodies Used with C1.18.4

Key Points

• C1.18.4 is almost always used as a negative control alongside mouse IgG2a primary antibodies, especially those targeting cell surface antigens like MHC class I molecules.
• It is rarely, if ever, the subject of investigation itself—its role is to ensure experimental rigor by accounting for non-specific binding.
• In complex experiments, C1.184 may be used with isotype controls of other subclasses to provide comprehensive background assessment.

If you have a specific experimental context or citation, more tailored examples of antibody pairings may be available. For the most common uses, however, the above covers the typical antibodies and proteins used alongside C1.18.4 in the literature.

Clone C1.18.4 is a mouse IgG2a isotype control antibody used extensively in immunological and biomedical research to control for non-specific binding—rather than to study any biological target or effect itself. Key findings from its citations in scientific literature focus on its role as an experimental control, not as a probe for a biological process or marker.

Key supported roles and findings:

• Standard Isotype Control: C1.18.4 is cited across immunology, oncology, and cell biology literature as the gold standard for negative control, matching the isotype, subclass, and species of experimental antibodies but lacking known binding specificity to targets in the host system.
• Control for Nonspecific Binding: In experiments measuring antibody binding (e.g., flow cytometry, immunohistochemistry), C1.18.4 allows researchers to differentiate true signal from background or non-specific interactions, ensuring the specificity of primary antibody staining.
• In Vivo and In Vitro Applications: This clone is validated for both live animal studies and cell/tissue analyses, chosen for its consistent lack of reactivity with mouse, rat, and human tissues—making it broadly applicable.

Nature of Citations:

• Experimentally Focused, Not Conceptual Discovery: Publications cite C1.18.4 to document the rigorous use of proper controls rather than to attribute any mechanism or discovery to the antibody itself. For example, in studies assessing checkpoint inhibitor effects or cancer immune evasion, C1.18.4 is listed as the negative control group for IgG2a isotype antibodies (see also for typical experimental contexts, though no explicit biological results are tied to C1.18.4).
• Methodological Reference: Research does not report unique biological findings or effects attributed to C1.18.4 beyond confirming its performance as a non-binding negative control.

Summary Table: Key Points about Clone C1.18.4

If you are seeking findings related to biological activity, mechanism, or phenotype linked specifically to C1.18.4, no such results exist in scientific literature; citations exclusively validate its use as a negative control.

Dosing Regimens of Clone C1.18.4 in Mouse Models

Clone C1.18.4 is a mouse IgG2a isotype control antibody, widely used as a negative control in immunological experiments to assess non-specific binding and establish baseline immune responses. Its primary utility lies in experimental control rather than therapeutic targeting, which influences how it is used and dosed in mouse studies.

General Dosing Approach

• No Standardized Dosing: There is no universally standardized dosing regimen for C1.18.4 in mouse models. Its administration is typically matched to the dosing strategy (route, concentration, frequency) of the active experimental antibody it is being compared against, rather than being individually optimized for efficacy.
• Route of Administration: C1.18.4 is commonly delivered via intraperitoneal (IP) injection, mirroring the route used for the primary experimental antibody. This ensures comparability when assessing the effects of the treatment antibody versus the isotype control.
• Dosing Frequency and Duration: The schedule (e.g., weekly, biweekly) and duration of administration are also matched to the experimental protocol of the primary antibody. This alignment is critical for interpreting whether observed effects are due to specific antibody-antigen interactions or non-specific immune modulation.

Specific Examples and Variability

• Recent Study Example: In a study published in Nature, an afucosylated version of mouse IgG2a (C1.18.4) was administered intraperitoneally at 5 mg/kg, once daily. This demonstrates that dose and schedule can vary based on the experimental design and the specific modification of the antibody.
• Lack of Therapeutic Indication: Because C1.18.4 lacks biological activity, its dosing is not tailored to achieve a pharmacodynamic or pharmacokinetic endpoint. Instead, it is used to control for the non-specific effects of antibody administration.
• Application-Dependent Variations: The actual dose, frequency, and duration may differ across studies depending on the primary antibody’s regimen, the model (e.g., tumor, infection, autoimmunity), and the scientific question being addressed. For instance, a study investigating cancer immunotherapy might administer C1.18.4 alongside a checkpoint inhibitor, using the same schedule and route as the therapeutic antibody.

Key Considerations

• Experimental Design: Researchers must ensure that C1.18.4 is administered in a manner that allows direct comparison with the experimental antibody, minimizing confounding variables.
• Documentation: Published methods sections often note that C1.18.4 was given “at the same dose and schedule” as the test antibody, but specific details (e.g., mg/kg, IP vs. IV, daily vs. weekly) are determined by the primary experimental protocol.
• No Biological Endpoint: There is no evidence that C1.18.4 dosing is optimized for safety or efficacy, as it is not intended to have a biological effect.

Summary Table

Conclusion

Dosing regimens for clone C1.18.4 in mouse models are not fixed but are instead tailored to match the administration protocol of the experimental antibody under investigation. The primary goal is to provide a valid negative control, ensuring that any observed effects can be confidently attributed to the specific action of the test antibody rather than non-specific immune modulation. Researchers should carefully document the dosing strategy used in their specific model to ensure reproducibility and accurate data interpretation.