Anti-Mouse CD4 [Clone GK1.5] — Purified in vivo GOLD™ Functional Grade

The GK1.5 clone is a widely used monoclonal antibody in in vivo mouse studies for several purposes, particularly focused on the depletion of CD4+ T cells. Here's an overview of its use:

Uses of GK1.5 in In Vivo Mouse Studies

1. CD4+ T Cell Depletion: GK1.5 is primarily used to deplete CD4+ T cells in vivo. This depletion is crucial for studying the role of CD4+ cells in immune responses, autoimmune diseases, and infections. By administering the GK1.5 antibody to mice, researchers can effectively reduce or eliminate CD4+ T cells, thereby analyzing their impact on various biological processes.

2. Blocking Helper T Cell Responses: The GK1.5 antibody can also block helper T cell responses to MHC class II antigens. This includes functions such as cytolysis, proliferation, allogeneic B cell help, and lymphokine release. This capability makes it useful for investigating the mechanisms of immune responses and potential therapeutic targets.

3. Research Models: GK1.5 has been utilized in various research models, including studies on autoimmune arthritis and HIV infection. For example, it has been shown to reduce disease severity in models of autoimmune arthritis by decreasing cytokine production and joint injury.

4. Immunological Studies: Beyond depletion, GK1.5 can be used in flow cytometry for identifying CD4+ T cells, allowing researchers to analyze cell populations and their changes following depletion.

Technical Considerations

• Isotype Control: When using GK1.5 for in vivo studies, researchers often use a rat IgG2b isotype control to ensure that observed effects are specific to CD4+ T cell depletion and not due to non-specific binding.
• Conjugation and Buffer: The antibody is typically unconjugated but can be conjugated for specific applications. It is recommended to use buffers like InVivoPure pH 6.5 Dilution Buffer for in vivo applications to minimize endotoxin levels and ensure compatibility with animal models.

In summary, the GK1.5 clone is a powerful tool in immunology research, enabling the study of CD4+ T cell functions and their impact on various diseases in mouse models.

Based on the available information, several antibodies and proteins are commonly used alongside or in comparison with the GK1.5 anti-CD4 antibody in research applications.

Competing and Related CD4 Antibodies

The RM4-5 antibody is frequently mentioned in conjunction with GK1.5, as it can block the binding of GK1.5 to CD4+ T cells, indicating they likely target overlapping or adjacent epitopes on the CD4 molecule. In contrast, the RM4-4 antibody does not interfere with GK1.5 binding, suggesting it recognizes a different epitope.

The YTS 177 and YTS 191 clones have been shown to compete directly with GK1.5 for CD4 binding, making them important comparative reagents in studies examining CD4 epitope mapping and functional blocking.

Isotype and Control Antibodies

For proper experimental controls, the LTF-2 monoclonal antibody serves as the recommended rat IgG2b isotype control for GK1.5. This antibody reacts with keyhole limpet hemocyanin (KLH), which is not expressed by mammals, making it an ideal negative control for both in vivo and in vitro applications.

Specialized Formats and Derivatives

Researchers have developed modified versions of GK1.5 for specific applications. The GK1.5 cys-diabody (cDb) represents an engineered antibody fragment designed for positron emission tomography (PET) imaging of CD4+ T cells. This format has been radiolabeled with ??Zr for immunoPET studies and has shown promise as a biologically inert imaging probe when used at appropriate doses.

Buffer Systems

The InVivoPure pH 6.5 Dilution Buffer is specifically formulated for use with GK1.5 and other in vivo antibodies. These buffers are designed with ultra-low endotoxin levels and have been screened for murine pathogens to meet the stringent requirements of in vivo research applications.

The literature suggests that GK1.5 is most commonly used in conjunction with these related CD4-targeting antibodies for comparative studies, appropriate isotype controls for experimental validation, and specialized buffer systems optimized for in vivo applications.

Key Scientific Findings Related to Clone GK1.5

Clone GK1.5 is a monoclonal antibody that specifically targets mouse CD4, a 55 kDa cell surface glycoprotein critical for T helper cell function, thymocyte development, and immune regulation. Below is a synthesis of the most significant findings from the scientific literature based on the citations and sources provided.

Functional Properties of GK1.5

• Blocking CD4-Mediated Cell Adhesion and T Cell Activation: GK1.5 is well documented for its ability to block CD4-mediated cell adhesion and inhibit T cell activation, which makes it a powerful tool for modulating immune responses in mouse models.
• Epitope Specificity: The binding of GK1.5 to CD4+ T cells can be competitively blocked by the RM4-5 antibody, but not by RM4-4, indicating distinct, non-overlapping epitopes on the CD4 molecule.
• Depletion of CD4+ T Cells In Vivo: GK1.5 is frequently used for the in vivo depletion of CD4+ T cells in mice. Studies have shown that GK1.5-mediated depletion can significantly reduce disease severity in models of autoimmune arthritis and attenuate progression in models of viral infection.
• Applications Beyond Depletion: In addition to depletion, GK1.5 is used in immunoprecipitation, immunohistochemical staining, and spatial biology techniques such as IBEX.

Impact on Immune Studies

• Therapeutic Potential in Autoimmunity: In a murine model of autoimmune arthritis, GK1.5-mediated CD4+ T cell depletion led to decreased disease severity, reduced cytokine production, and less joint injury, highlighting its therapeutic potential for autoimmune diseases.
• Viral Infection Models: In a mouse model of HIV infection, treatment with GK1.5 antibodies reduced viral load and delayed disease progression, demonstrating the critical role of CD4+ T cells in viral pathogenesis and the utility of GK1.5 in studying host–pathogen interactions.
• Molecular Imaging: Low doses of a GK1.5-based antibody fragment (cys-diabody) enabled high-contrast immunoPET imaging of CD4+ T cells with minimal impact on T cell biology, suggesting its utility for non-invasive monitoring of immune responses in vivo. However, higher doses caused transient downmodulation of CD4 expression and inhibited T cell proliferation, underscoring the importance of dose optimization in experimental designs.

Technical Considerations

• Antibody Purity for Sensitive Assays: For in vivo studies or highly sensitive applications, ultra-low endotoxin (Ultra-LEAF™) formulations of GK1.5 are recommended to minimize potential confounding effects from endotoxin contamination.
• Distinct Epitopes for Flow Cytometry: Because GK1.5 can induce CD4 downmodulation or block staining by other GK1.5-based reagents, flow cytometry studies of CD4 expression after GK1.5 treatment should use antibodies like RM4-4 that recognize non-overlapping epitopes.

Summary Table: Key Applications and Findings

Conclusion

Clone GK1.5 is a cornerstone reagent in mouse immunology, enabling precise manipulation and study of CD4+ T cell biology. Its ability to deplete, block, and image CD4+ cells has advanced our understanding of autoimmunity, infection, and immune regulation, while careful consideration of dose and antibody purity is essential to avoid experimental artifacts.

Dosing regimens of clone GK1.5, an anti-mouse CD4 monoclonal antibody, vary widely across mouse models depending on experimental objectives, mouse strain, route of administration, and required depletion depth.

Key contexts and details:

• Typical Dose Range: The commonly reported dose range is 50–500 ?g per injection for effective CD4 T cell depletion in mice. A more specific standard dosing regime for depletion studies is 200–250 ?g per mouse, typically given intraperitoneally 2–3 times per week. Some protocols recommend as little as 5–50 ?g per mouse (intravenous), though such low doses are generally not used for robust depletion.
• Route & Frequency: The preferred route is usually intraperitoneal injection, though intravenous has been used, notably at lower doses. The frequency depends on the desired length of depletion but is most commonly every 2–3 days.
• Experimental Variables: The optimal dose can vary by mouse strain, age, health status, and experimental goal. For instance, young or immunodeficient mice may require lower doses. Studies focusing on blocking helper function rather than full depletion may also use lower or single doses.
• Dose-dependent Effects: Lower doses (e.g., 2–40 ?g) can cause partial and tissue-dependent effects on CD4 expression or function rather than complete depletion. For example, 40 ?g of a cys-diabody format of GK1.5 transiently suppressed CD4 expression and T cell proliferation in lymph nodes, but not in spleen; by contrast, 2 ?g had minimal impact.
• Alternative Clones/Species: GK1.5 is mouse-specific; for rat models, W3/25 is used for analogous depletion.

Summary Table: GK1.5 Dosing Across Common Mouse Models

Critical points:

• Dose should be titrated for each experiment; complete depletion is not always required or desirable.
• Overdosing can cause off-target effects or toxicity, so confirmation via flow cytometry is standard practice after initial dosing.
• For other species or models, verify cross-reactivity or use a species-appropriate depletion antibody.

In sum, dosing of GK1.5 for CD4+ T cell depletion in mice is typically 200–250 ?g per injection intraperitoneally, 2–3 times per week, but can range from 50–500 ?g per injection and should be tailored to mouse strain, age, and experimental needs. Lower or single doses can be used for functional blocking rather than outright depletion.