CARD9 Antibody

What are the recommended applications for CARD9 antibodies in research settings?

CARD9 antibodies have been validated for multiple research applications with varying protocols:

Most commercial CARD9 antibodies target the full-length protein or specific domains and show reactivity with human and mouse samples, with predicted reactivity in rat, pig, zebrafish, bovine, and other species based on sequence homology . For optimal results, validation in your specific experimental system is recommended, as observed molecular weights may vary between 55-62 kDa depending on sample preparation and post-translational modifications .

How should researchers verify CARD9 antibody specificity for their experimental system?

Antibody validation should include multiple complementary approaches:

• Positive and negative controls: Use samples with known CARD9 expression (e.g., THP-1 cells as positive controls)

• Knockout/knockdown validation: Test antibody specificity using CARD9 knockout or knockdown samples

• Peptide competition assay: Pre-incubate antibody with immunizing peptide to confirm specific binding

• Cross-reactivity assessment: Test against related CARD family proteins

• Multiple antibody comparison: Use different CARD9 antibodies targeting distinct epitopes to confirm staining patterns

Published literature has utilized CARD9 knockout models to validate antibody specificity, with several studies using the CARD9 antibody in knockout validation experiments .

What is the expression pattern of CARD9 across different tissues and cell types?

Understanding CARD9 expression is crucial for experimental design and interpreting antibody staining results:

Human CARD9 expression:

• Highest expression: Monocytes, granulocytes, testicle, blood, spleen

• Moderate expression: Bone marrow stromal cells, endometrium, lung

• Also detected in: Liver, placenta, peripheral blood leukocytes, brain

Mouse Card9 expression:

• Highest expression: Granulocytes, bone marrow, ileum, olfactory bulb

• Also expressed in: Thymus, lung, cerebellum, jejunum, spleen, cerebellar cortex

Recent research has revealed that CARD9 expression extends beyond myeloid cells to include T and B lymphocytes in both humans and mice, suggesting previously unrecognized roles in lymphoid function . This finding has important implications for experimental design when studying CARD9 in the context of adaptive immunity.

How should researchers design experiments to study CARD9 signaling complexes?

CARD9 functions within multiprotein signaling complexes that can be studied using antibody-based approaches:

• Co-immunoprecipitation (Co-IP):

  • Use anti-CARD9 antibodies to pull down the protein complex

  • Identify interaction partners (BCL10, MALT1, TRIM62) by western blot

  • Include appropriate controls (IgG control, lysate input)

• Proximity Ligation Assay (PLA):

  • Combine anti-CARD9 antibody with antibodies against suspected interaction partners

  • Visualize protein-protein interactions in situ within cells

• CBM Complex Evaluation:

  • Co-transfect CARD9 with TRIM62, MALT1, and BCL10 expression plasmids

  • Perform co-immunoprecipitation to evaluate complex composition

Research has identified that CARD9 forms a trimolecular complex with BCL10 and MALT1 (the CBM complex) after receptor stimulation, which activates the canonical NF-κB pathway . Advanced methodologies can help elucidate how mutations affect this complex formation.

How can researchers study CARD9 activation states using antibodies?

CARD9 undergoes specific structural changes and post-translational modifications during activation that can be monitored using antibody-based approaches:

• Phosphorylation-specific antibodies:

  • Monitor CARD9 phosphorylation status following stimulation

  • Key sites include those modified by PKCδ and Syk kinases

• Structural conformation assays:

  • CARD9 exists in an autoinhibited state prior to activation

  • The CARD-coiled-coil interface is crucial for autoinhibition

  • Use antibodies recognizing exposed epitopes during activation

• Oligomerization detection:

  • Upon activation, CARD9 homooligomerizes to form a nucleating helical template

  • Use crosslinking followed by western blot to detect oligomers

• Ubiquitination analysis:

  • CARD9 ubiquitination at Lys125 by TRIM62 is required for signal propagation

  • Use anti-ubiquitin antibodies in combination with CARD9 IP

Research has revealed two distinct mechanisms of CARD9 activation: (1) CARD11-like activation through phosphorylation and (2) CARD9-specific ubiquitination that disrupts the autoinhibitory interface .

How can CARD9 antibodies be utilized to study fungal infection models?

CARD9 plays a critical role in antifungal immunity, particularly against Candida species:

• Infection response monitoring:

  • Track CARD9 expression changes in infected vs. uninfected tissues

  • Compare wild-type and CARD9-deficient models using antibody staining

  • Monitor recruitment of CARD9+ cells to infection sites

• CLR-dependent vs. CLR-independent pathways:

  • Use stimulation with specific fungal PAMPs (e.g., β-glucans, mannans)

  • Monitor CARD9 activation in response to different stimuli

  • Compare responses across different tissue environments

• Organ-specific roles:

  • CARD9 exhibits different functions depending on tissue context

  • For kidney infection models: Monitor cytokine profiles (IL-1α, IL-1β, IL-6, CCL2, TNF-α)

  • For CNS infection models: Assess neutrophil migration via CXCL1 production

Research has shown that CARD9 plays species- and organ-specific roles in neutrophil accumulation during Candida infections, with both CLR-dependent and CLR-independent functions documented .

How can CARD9 antibodies be used to investigate inflammatory bowel disease mechanisms?

CARD9 has been implicated in inflammatory bowel disease (IBD) pathogenesis:

• CARD9 variant analysis:

  • The c.IVS11+1G>C variant creates two mutant transcripts:

    • Out-of-frame c.1358-1434 deletion (~55 kDa protein)

    • In-frame c.1417-1434 deletion (~61 kDa protein)

  • Use appropriate antibodies to distinguish these variants

• Mycobiota influence assessment:

  • CARD9 regulates intestinal fungal communities (mycobiota)

  • Use intestinal tissue staining to correlate CARD9 expression with fungal presence

• Dendritic cell-driven inflammation:

  • CARD9 mediates Toll-like receptor signaling in dendritic cells

  • Compare wild-type and CARD9-deficient dendritic cells

  • Assess cytokine production (TNF, IL-23, IL-6) following stimulation

Research has demonstrated that CARD9 amplifies Toll-like receptor signaling and cytokine production in Lyn-deficient bone marrow-derived dendritic cells. Deletion of Card9 reduced the development of both spontaneous autoimmune disease and DSS- or IL-10 deficiency-associated colitis in Lyn-/- mice .

What are the methodological approaches for studying CARD9 structure-function relationships?

Understanding CARD9 structure-function relationships requires specialized techniques:

• Domain-specific antibodies:

  • Target specific regions (CARD domain, coiled-coil domain, linker region)

  • Use for mapping functional domains in cellular assays

• Structure-guided mutagenesis:

  • Target residues at the CARD-coiled-coil interface

  • Assess effects on autoinhibition and activation

  • The L85Y mutation is known to be activating despite lowered protein expression

• Filament formation analysis:

  • CARD9 forms helical filaments during activation

  • Use electron microscopy and in vitro reconstitution assays

  • CARD9-templated Bcl10 polymerization can be visualized with appropriate antibodies

Recent structural studies have elucidated the autoinhibited state of CARD9, showing an extensive interface between its caspase recruitment domain (CARD) and coiled-coil domain. Disruption of this interface leads to hyperactivation and formation of Bcl10-templating filaments .

How can researchers analyze CARD9 mRNA splice variants?

CARD9 alternative splicing produces functionally distinct protein variants:

• Transcript analysis protocol:

  • Extract total RNA from PBMCs

  • Reverse transcribe to cDNA

  • PCR-amplify using exon-specific CARD9 primers

  • For quantitative analysis, use exon-specific TaqMan probes (e.g., CARD9 exon 11-specific probe)

• Protein variant detection:

  • Select antibodies recognizing regions common to all variants

  • Use western blotting to identify size differences

  • Expected sizes: Wild-type (~62kDa), Δexon11 variant (~55kDa), Δ18nt variant (~61kDa)

Research has shown that CARD9 splice variants differ in their ability to form functional CBM complexes. Neither the Δexon11 nor the Δ18nt variant can form a complete functional CBM complex that includes TRIM62 .

How can CARD9 antibodies be utilized in Alzheimer's disease research models?

Recent research has identified a novel role for CARD9 in Alzheimer's disease pathology:

• Amyloid-β (Aβ) clearance studies:

  • Compare CARD9 wild-type and knockout models in 5xFAD mice

  • Use immunohistochemistry to quantify Aβ burden

  • Assess microglial activation states with co-staining approaches

• Pharmacological CARD9 activation:

  • Monitor effects on Aβ clearance in the hippocampus

  • Evaluate microglial phenotypes before and after treatment

  • Assess cognitive outcomes in treated vs. untreated models

• Downstream signaling analysis:

  • CARD9 may connect innate immune receptors (TREM2, CD33, CD22) to intracellular signaling

  • Use phospho-specific antibodies to monitor activation of downstream pathways

Research has demonstrated that genetic ablation of CARD9 in the 5xFAD mouse model results in exacerbated amyloid beta deposition, increased neuronal loss, worsened cognitive deficits, and alterations in microglial responses. Conversely, pharmacological activation of CARD9 promotes improved clearance of Aβ deposits .

What are the methodological considerations when studying CARD9 in central nervous system fungal infections?

CARD9 is critical for CNS antifungal immunity:

• CARD9-dependent neutrophil recruitment:

  • Assess neutrophil migration to fungal-infected CNS

  • Monitor CXCL1-dependent pathways

  • Evaluate p38/c-fos-dependent IL-1β production in microglia

• Blood-brain barrier studies:

  • CARD9 deficiency impacts neutrophil migration across the blood-brain barrier

  • Use immunofluorescence to track labeled neutrophils in relation to CARD9 expression

• Organ-specific protection mechanisms:

  • Human CARD9 deficiency is associated with CNS fungal infections

  • Compare tissue-specific CARD9 expression and function

  • Assess pathogen-specific responses within the CNS microenvironment

Research has shown that CARD9 mediates p38/c-fos-dependent IL-1β production in microglia, which promotes CXCL1-dependent neutrophil migration to the fungal-infected central nervous system, a critical mechanism for CNS protection against fungal pathogens .

How can researchers investigate CARD9's role in antibody responses to fungal pathogens?

CARD9 mediates connections between innate and adaptive immunity:

• Antifungal IgG production assays:

  • Compare serum antifungal IgG levels in wild-type vs. CARD9-deficient models

  • Assess germinal center (GC)-dependent B cell expansion in extraintestinal lymphoid tissues

  • Evaluate protection against disseminated Candida infection

• CX3CR1+ macrophage involvement:

  • Use co-staining to identify CARD9+CX3CR1+ macrophages

  • Assess their role in antifungal IgG production

  • Compare findings in models with CARD9 mutations vs. wild-type

• Gut mycobiota influence:

  • Analyze how commensal fungi in the gut shape antibody responses

  • Evaluate CARD9-dependent systemic protection mechanisms

  • Correlate with antifungal IgG titers in circulation

Research has shown that fungal colonization of the gut induces germinal center-dependent B cell expansion in extraintestinal lymphoid tissues and generates systemic antibodies that confer protection against disseminated Candida infections. This process depends on CARD9 and CARD9+CX3CR1+ macrophages .

What methods can be used to study CARD9's role in T cell responses?

CARD9 influences T cell polarization and function:

• Th17 commitment evaluation:

  • Isolate total PBMCs from control and CARD9-deficient subjects

  • Assess Th17 polarization by flow cytometry

  • Evaluate IL-17 production in response to fungal stimuli

• T cell-specific CARD9 expression:

  • Sort T cells from spleen using appropriate markers

  • Perform western blotting to detect CARD9 expression

  • Compare with expression in myeloid cells

• Cytokine production assessment:

  • Stimulate PBMCs with heat-killed Candida (HKC) or LPS

  • Evaluate cytokine production profiles using Luminex or ELISA

  • Compare responses between normal controls and CARD9-deficient patients

Recent research has revealed CARD9 expression in T and B lymphocytes in both humans and mice, suggesting a previously unrecognized role in lymphoid function beyond the well-established role in myeloid cells .

How can CARD9 antibodies be used to identify patients with CARD9 deficiency?

CARD9 deficiency is an autosomal recessive primary immunodeficiency:

• Protein expression analysis:

  • Use western blotting on patient-derived PBMCs

  • Compare expression levels with healthy controls

  • Identify truncated or absent CARD9 protein

• Functional assays:

  • Assess cytokine production after fungal stimulation

  • Evaluate NF-κB pathway activation

  • Compare with known CARD9-deficient controls

• CBM complex assessment:

  • Evaluate ability to form functional complexes with BCL10, MALT1, and TRIM62

  • Distinguish between complete loss-of-function and hypomorphic variants

Clinical research has identified CARD9 deficiency patients with both homozygous and compound heterozygous mutations. These patients often present with chronic mucocutaneous candidiasis, invasive fungal infections, and sometimes a CVID-like phenotype with hypogammaglobulinemia .

What are the emerging areas of CARD9 antibody applications in research?

Several cutting-edge applications are expanding our understanding of CARD9 biology:

• Single-cell analysis:

  • Single-cell protein expression profiling

  • Integration with transcriptomic data

  • Identification of novel CARD9-expressing cell populations

• Therapeutic targeting:

  • Development of CARD9 activators for neurodegenerative diseases

  • Targeting CARD9 to modulate inflammatory responses in IBD

  • Enhancing antifungal immunity in immunocompromised patients

• Microbiome-immune interactions:

  • CARD9's role in regulating intestinal mycobiota

  • Effects on bacterial microbiome composition

  • Influence on systemic immunity beyond the gut