Anti-Mouse CD40 [Clone FGK4.5] — Purified in vivo PLATINUM™ Functional Grade

Clone FGK4.5 is an agonistic anti-mouse CD40 monoclonal antibody widely used in in vivo mouse studies to activate CD40-expressing antigen-presenting cells (APCs), such as B cells, dendritic cells, and macrophages. This activation simulates CD40-CD154 (CD40L) interactions, leading to downstream immune stimulation and modulation in experimental models.

Key uses and experimental details in in vivo mouse studies:

• Immune Cell Activation: FGK4.5 (sometimes labeled FGK45, as nomenclature varies across sources but refers to the same clone) is typically administered intraperitoneally (i.p.), with a commonly effective dose cited as 100??g per mouse.
• Mechanism: The antibody acts as an agonist for the CD40 receptor and its bioactivity critically depends on engagement of Fc?RIIB receptors on immune cells in vivo. This means its stimulatory activity is partly mediated via the Fc domain interacting with Fc? receptors, which modulates signal strength and cellular outcomes.
• Readouts: After administration, mice are typically evaluated for upregulation of activation markers (e.g., MHC class I/II, CD80, CD86) on B cells and macrophages using flow cytometry, usually 24–48 hours post-injection.
• Experimental Applications: The clone is used to:
  • Activate the immune system to study pathways of inflammation, tolerance, or autoimmune disease.
  • Test immunotherapeutic strategies in cancer or infection models by stimulating dendritic cell and T cell activation.
  • Investigate CD40 signaling in B cell development, isotype switching, and germinal center formation.

Summary of recommendations and considerations:

• FGK4.5 is most potent in wild-type mice, since some activation effects (especially full marker upregulation) are reduced in Fc?RIIB-deficient strains.
• Used primarily at 100??g i.p. per mouse, but titration may be necessary for specific models or endpoints.
• Control antibodies (isotype controls) are used to distinguish specific effects of anti-CD40 engagement.

Alternative uses:

• Besides in vivo activation, clone FGK4.5 can be used for flow cytometry, immunoprecipitation, and immunohistochemistry to detect CD40 on tissues or cells.

In summary, FGK4.5 is injected into mice to activate CD40, thereby stimulating APCs and modulating immune responses to study immune function or intervention strategies.

Commonly used antibodies or proteins in combination with FGK4.5 (an agonistic anti-mouse CD40 monoclonal antibody) in the literature include immune activation and co-stimulatory markers such as MHC class II, MHC class I (H-2D^b^), CD80, and CD86.

Essential context and supporting details:

• FGK4.5 is primarily used to activate mouse antigen-presenting cells, including B cells and macrophages, via CD40 ligation.
• Studies evaluating FGK4.5 effects typically monitor upregulation of activation markers. Most notably:
  • MHC class II and MHC class I (H-2D^b^) for antigen presentation.
  • CD80 and CD86 as co-stimulatory molecules that are critical in T-cell priming and activation.
• In experimental settings, isotype control antibodies are commonly used alongside FGK4.5 to establish specificity of immune effects.
• FGK4.5 is frequently used in combination immunotherapy experiments, sometimes with other immune checkpoint or co-stimulatory reagents, such as agonists to CD28, anti-CTLA-4, anti-PD-1/PD-L1, or with CD40L (CD154) for further modulation of T-cell and B-cell responses (though direct combinations with these were not explicitly stated in the retrieved search—this inference is based on common immunological practice).

Summary Table: Commonly Used Antibodies/Proteins with FGK4.5

Additional relevant information:

• Other anti-mouse CD40 monoclonal antibodies (such as 1C10 and 3/23) are sometimes reported in the same experimental settings for methodological comparisons.
• The activity of FGK4.5 itself is shown to involve Fc gamma receptor engagement (especially Fc?RIIB), so antibodies targeting Fc?R may also be relevant in mechanistic immunology studies.

There is limited evidence in the provided results for use with particular therapeutic antibodies (e.g., anti-PD-1), but such combinations are common in the field, as inferred from general immunology practice (this is acknowledged as an informed extrapolation rather than explicit citation from the listed search results).

Clone FGK4.5 (also referred to as FGK45) is a widely used monoclonal antibody that specifically targets mouse CD40 and is extensively cited in immunology research. Key findings from scientific citations of clone FGK4.5 include:

• Potent Agonist of CD40: FGK4.5 is functionally active for both in vitro and in vivo activation of CD40-expressing antigen-presenting cells, including dendritic cells, B cells, and macrophages. Activation of CD40 by this antibody promotes T-cell dependent immunoglobulin class switching, germinal center formation, and memory B cell development.
• Activation and Polarization of Macrophages: Recent literature demonstrates that FGK4.5 stimulation of macrophages induces a profound metabolic reprogramming. It increases lipid uptake, mitochondrial activity, and rewires fatty acid/glutamine metabolism to promote pro-inflammatory gene expression and cytokine production in a manner dependent on metabolic enzymes like ACLY and LDHA.
• Epigenetic Regulation: FGK4.5 engagement of CD40 leads to increased histone acetylation (notably H3K27ac) through acetyl-CoA generated from fatty acid oxidation, which is essential for the induction of pro-inflammatory genes.
• Tumor Immunotherapy Applications: In preclinical models, FGK4.5-mediated CD40 activation improves responses to immune checkpoint blockade (such as anti-PD-1 therapy), and its anti-tumor efficacy is linked to the metabolic state and polarization of tumor-associated macrophages.
• B Cell Activation: FGK4.5 directly stimulates mouse B cell proliferation and can block the binding of certain other anti-CD40 antibodies (such as HM40-3).
• Versatile Experimental Use: The antibody is used for cell surface staining (flow cytometry), in vitro activation, in vivo immune modulation, and functional neutering/blocking experiments in mice.

Summary Table: Key Research Applications of Clone FGK4.5

Notable Citations: Landmark studies using FGK4.5 include research into immune activation (Andersson J et al., Immunity 1996; Melief CJ et al., Nature 1998), immunotherapy (Tominaga T et al., Neuro Oncol 2015), and mechanistic studies of metabolic-epigenetic crosstalk in macrophages (Nature, 2023).

FGK4.5 remains a foundational tool for delineating CD40-mediated immune mechanisms in mouse models, particularly in the fields of immunometabolism, infectious disease, and cancer immunology.

Dosing regimens of clone FGK4.5 (anti-mouse CD40 antibody) vary by mouse model, disease context, and experimental goals, typically ranging from single to repeated doses between 3–5 mg/kg administered intraperitoneally.

Essential context from the search results:

• Pancreatic tumor (Pan02) model: FGK4.5 was given at 3 mg/kg on days 7, 14, and 21 (i.e., three weekly doses), with effects evaluated shortly after the last dose.
• B cell and macrophage activation (general in vivo model): A related antibody, FGK45 (equivalent to FGK4.5), was administered at 100 ?g per mouse intraperitoneally as a single dose, which gave optimal immune activation in wild-type mice. Higher doses (e.g., 5 mg/kg) have been used when direct comparison to human therapeutic antibodies was required.
• Glioma mouse models: FGK45 was used in a dose-dependent manner, but the specific range is not stated in the search results.

Additional details:

• Route of administration: Doses are most commonly given intraperitoneally. Some protocols may use intravenous routes for specific purposes, but intraperitoneal is standard.
• Schedule: The schedule varies—some studies use single doses, while others use multiple doses spaced a week apart (common in tumor therapy settings).
• Mouse strain and disease setting: Regimens may need modification depending on mouse strain, model, and tissue target due to differences in antibody clearance and immune context.

Regimen selection rationale:

• Higher or repeated doses are typically used for tumor immunotherapy to sustain immune activation.
• Lower, single doses may be sufficient for acute immune activation studies.
• Crosslinking and Fc? receptor engagement are critical for this antibody's agonist function in vivo, which can influence dosing efficacy.

If specific mouse strains or disease models are of interest, protocols may need further adjustment based on published literature for those settings.