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

Clone GK1.5 is a rat anti-mouse monoclonal antibody specifically targeting the CD4 antigen, and in in vivo mouse studies, it is primarily used for the depletion of CD4+ T cells to study their functional roles in immunity, disease, and therapeutic models.

Key uses and details:

• CD4+ T cell depletion: The main in vivo application of GK1.5 is to selectively remove (deplete) CD4+ T cells from mice by systemic administration of the antibody. This allows researchers to assess the role of CD4+ T cells in physiological or pathological processes, such as autoimmunity, infection, cancer, or transplantation models.

• Mechanism: GK1.5 binds to the CD4 glycoprotein on the surface of helper T cells (as well as thymocytes and some dendritic cells and macrophages), marking them for depletion through Fc-mediated immune mechanisms.

• Blockade of CD4 function: Besides cell depletion, GK1.5 can functionally block CD4, inhibiting helper T cell responses to MHC Class II antigens, thus providing insight into T cell–dependent immune interactions.

• Experimental applications: GK1.5 is also employed for flow cytometry, immunohistochemistry, and cell separation, though its depletion/blocking function is the primary in vivo use.

Typical protocols involve repeated intraperitoneal or intravenous injections of GK1.5, leading to effective and often near-complete depletion of peripheral CD4+ T cells for several days to weeks, depending on the dosing regimen. These experiments often use isotype controls and low-endotoxin preparations to avoid nonspecific effects.

Examples from the literature:

• In a mouse model of autoimmune arthritis, GK1.5-mediated CD4+ T cell depletion reduced disease severity by lowering cytokine production and joint injury.
• In infectious disease models, such as HIV mouse models, GK1.5 treatment reduced viral load and disease progression.

Preparation for in vivo use: GK1.5 antibodies formulated for in vivo work are usually highly purified, low in endotoxin, and free of preservatives and carrier proteins to reduce immunogenicity and toxicity.

In summary, clone GK1.5 is a critical experimental tool enabling the controlled removal or functional blockade of CD4+ T cells in mice, illuminating their roles across a range of immunological studies.

Commonly used antibodies or proteins paired with GK1.5 (anti-mouse CD4) in the literature depend on the experimental goal but often include markers relevant to T cell subsets, isotype controls, and depletion strategies.

Frequently Used Antibodies/Proteins with GK1.5

• CD8 Antibodies (such as 53-6.7): These identify and/or deplete CD8+ T cells and are often used together with CD4 (GK1.5) for characterizing or sorting lymphocyte populations in flow cytometry, immunohistochemistry, or in vivo depletion experiments.

• Isotype Controls for Rat IgG2b: These are used to control for non-specific binding of GK1.5, which is a rat IgG2b. For example, anti-keyhole limpet hemocyanin (KLH, clone LTF-2) is a common isotype control.

• Other T cell markers:

  • CD3 antibodies: Target all T cells, often used in multi-marker panels for flow cytometry or immunohistochemistry alongside CD4.
  • CD45 (pan-leukocyte marker): Helps further identify leukocyte populations in conjunction with CD4 and other T cell markers.

• Alternative anti-CD4 antibodies: Such as clones YTS 191.1 and RM4-5 for experimental comparisons. These may have different blocking or depleting properties and competitive binding relationships with GK1.5.

• Functional/Activation Markers:

  • CD25 (IL-2R?), CD44, CD62L: Distinguish active or memory vs. naive T cells, frequently stained together with CD4 (GK1.5) in phenotyping panels.

• Antibodies for additional cell types:

  • Gr-1, F4/80, B220/CD19: For studying myeloid or B cell populations in parallel with CD4+ T cells.

Experimental Controls and Other Protein Tools

• Isotype-Matched Rat IgG2b Antibodies: Used as negative controls to distinguish specific from non-specific binding effects.
• Dilution Buffers and Ultra-Low Endotoxin Formulations: For in vivo studies, special buffers and highly purified antibody preparations (e.g., Ultra-LEAF™) are recommended to avoid confounding immune effects.

Recently Cited Literature Practices

• Studies depleting both CD4+ (GK1.5) and CD8+ (53-6.7) T cells to examine specific immune roles in autoimmunity, infection, and cancer models.
• Use of antibodies such as RM4-5 (another anti-CD4 clone) alongside GK1.5 to study competitive epitope binding or to compare blocking vs. depleting capabilities.

Summary Table: Common Markers Used with GK1.5

The exact combination depends on your experimental question, but most studies involving GK1.5 routinely use complementary T cell subset markers, appropriate isotype controls, and sometimes other depletion antibodies to interrogate complex immune populations.

Clone GK1.5 is a well-established monoclonal antibody targeting mouse CD4, widely cited for its ability to deplete, block, and identify CD4? T cells in immunological research. Key findings from scientific literature cite the following core applications and insights:

• In Vivo and In Vitro T Cell Depletion and Blockade:

  • GK1.5 is routinely used to efficiently deplete CD4? T cells in mice, enabling studies on immune responses, autoimmune diseases, viral infections, and transplantation. CD4 depletion using GK1.5 is a foundational technique for dissecting the role of T cells in experimental models.
  • For instance, in a murine autoimmune arthritis model, GK1.5-mediated depletion led to reduced disease severity, diminished cytokine production, and less joint injury, highlighting its role in studying pathogenesis and potential therapies.

• Mechanistic and Functional Studies:

  • GK1.5 blocks CD4-mediated cell adhesion and T cell activation by interacting with the CD4 molecule. Its binding can be specifically blocked by another clone, RM4-5, which recognizes a different CD4 epitope; but it is not blocked by RM4-4. This precise epitope targeting is important when selecting antibody combinations for multiparameter flow cytometry or depletion protocols.

• Immunophenotyping and Imaging:

  • GK1.5 is used in immunohistochemistry and flow cytometry for identifying and quantitating CD4? T cells in tissue and blood samples.
  • Modified fragments of GK1.5 (e.g., cys-diabody, cDb) are employed in immunoPET to nondestructively image CD4? T cell distributions in vivo. Studies show that low-dose GK1.5 cDb allows high imaging contrast with minimal, reversible impacts on T cell viability or function, making it a preferred approach for in vivo cell tracking.

• Effect on CD4 Expression and Function:

  • High doses of GK1.5 or its fragments can transiently downregulate CD4 expression on T cells—with effects reversing within days of administration. Very high concentrations can inhibit CD4? T cell proliferation and IFN-? production in vitro, so dosing and application must be carefully considered especially in functional studies.

• Breadth of Experimental Use:

  • Beyond depletion, GK1.5 is used for:
    • Blocking assays to study cell adhesion.
    • Immunoprecipitation of CD4 and its complexes.
    • Spatial biology techniques, such as multiplexed imaging.
    • Immunohistochemical staining of frozen tissue sections.

Summary Table: Core Applications and Findings for Clone GK1.5

Caveats:

• CD4 expression may be transiently reduced after antibody administration.
• Biological effects on T cell function and proliferation are dose-dependent, particularly for imaging and in vivo depletion protocols.

In summary, GK1.5 is one of the most cited and versatile tools for mouse CD4? T cell analysis, depletion, and blockade, underpinning fundamental discoveries in immunology, autoimmunity, infection, and therapeutic interventions.

Dosing regimens for the anti-mouse CD4 antibody clone GK1.5 vary across mouse models primarily in terms of dose, frequency, route of administration, and experimental objective. The most commonly reported regimens for in vivo CD4+ T cell depletion in mice are single or repeated intraperitoneal injections of 200–250??g per mouse, administered 2–3 times per week. However, doses as low as 50–500??g per injection have been used depending on the mouse strain, age, health status, and specific research goals.

Key variables and reported regimens:

• Dose per injection:

  • Most studies use 200–250??g per mouse.
  • Lower doses (as low as 50??g or even 2–40??g for engineered antibody fragments) may be sufficient for partial depletion or blocking studies, with higher doses yielding greater suppression of CD4 expression or function.
  • High doses (up to 500??g) are sometimes reported, especially in models requiring complete and fast depletion, or in older/larger mice.

• Dosing frequency:

  • 2–3 times per week is standard for sustained depletion.
  • Some protocols use a single high dose or daily low-dose regimens, particularly for short-term experiments.

• Route of administration:

  • Intraperitoneal injection is the most common, but intravenous injection (e.g., tail vein) and subcutaneous administration have also been used for specific applications.
  • Dosing adjustments may be necessary when switching routes due to differences in pharmacokinetics and tissue distribution.

• Mouse model variables:

  • Strain sensitivity: Some mouse strains may require dose adjustment due to inherent immunological differences.
  • Age and size: Juvenile mice may require lower doses relative to adults; individual optimization is recommended.

• Experimental goals:

  • Depletion (cell removal): Higher doses are typically used for robust depletion of CD4 T cells in autoimmune, cancer, transplant, or infection models.
  • Blockade (functional inhibition): Lower doses may be employed to transiently inhibit CD4 function without full depletion, particularly for imaging or mechanistic studies.

• Special antibody formats: Modified GK1.5 antibodies (e.g., cys-diabodies) can show dose-dependent effects distinct from standard monoclonals; for instance, 2??g caused mild effects while 40??g blocked proliferation in lymph nodes.

Summary Table: GK1.5 Dosing Regimens in Mouse Models| Application | Dose Range | Frequency | Route | Model Considerations ||----------------------------|---------------|-----------------|-------------------|----------------------------------|| Depletion | 200–250??g | 2–3x/week | Intraperitoneal | Standard, most strains || Partial depletion/blockade | 2–50??g | Single/multiple | Intravenous/IP | Imaging/blocking studies || Robust depletion | up to 500??g | Once or repeated| IP/IV | Large/older mice, fast effect |

Optimization is critical: Researchers are advised to run dose-response and time-course experiments to find the minimal sufficient dose for their specific strain, health context, and experimental aim. Off-target effects and incomplete depletion can occur if regimens are not tailored.

Alternative animal models and clones: GK1.5 is optimized for mouse models; other species may require alternative clones (e.g., W3/25 for rats).

In summary, while a regimen of 200–250??g intraperitoneally 2–3 times/week is commonly used for mouse T cell depletion, significant variation exists based on mouse model and experimental requirement, warranting pilot calibration before critical studies.