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.

The correct storage temperature for sterile packaged clone GK1.5 depends on the supplier and specific product formulation, but the most common recommendation is 2–8°C (refrigerator temperature), protecting the product from light, and without freezing. Some functional or in vivo grade formulations allow long-term storage at -20°C to -70°C, especially if aliquoted, but short-term storage (up to 1 month) is still 2–8°C.

Key details:

• For standard, ready-to-use or fluorescent conjugated GK1.5: 2–8°C; do not freeze.
• For functional-grade or in vivo-grade recombinant antibody: 2–8°C for up to one month, or -20°C to -70°C for long-term (avoid repeated freeze-thaw cycles).
• Always check the product datasheet, as diluents, preservatives, and conjugations may alter storage requirements.

If you have a sterile, undiluted, or conjugated GK1.5 antibody, store it at 2–8°C, avoiding freezing and light exposure unless the datasheet for your exact product explicitly states freezer storage is appropriate.

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.