SPAC11D3.11c Antibody

What are CD11c and CD11d antibodies and what cellular targets do they recognize?

CD11c (also known as Integrin alpha-X or ITGAX) antibodies recognize a heterodimeric glycoprotein consisting of an α- and β-subunit with seven repeating integrin domains. This transmembrane receptor type I plays crucial roles in T cell killing and mediates intercellular adhesions during inflammation. CD11c is predominantly expressed in dendritic cells, monocytes, macrophages, neutrophils, and a small subset of B cells .

CD11d antibodies target the CD11d/CD18 integrin, which is being studied as a potential therapeutic target for several pathophysiologies including neurotrauma, sepsis, and atherosclerosis. The CD11d subunit must pair with CD18 for functional expression on the cell surface .

What species reactivity can be expected from commercially available antibodies?

Antibody specificity varies significantly between species and must be carefully selected for the target organism:

When selecting antibodies, researchers should verify published reactivity data and perform appropriate validation for their specific experimental system .

What are the recommended storage and handling conditions for these antibodies?

For optimal performance and stability, researchers should adhere to specific storage guidelines:

CD11c antibody (HS-375 003): The lyophilized antibody should be stored at +4°C. After reconstitution with 200 μl H₂O, aliquot and store at -20°C to -80°C until use. Importantly, do not freeze when still lyophilized. Azide is typically added before lyophilization as a preservative .

Humanized anti-CD11d antibodies: While specific storage conditions were not detailed in the search results, monoclonal antibodies generally require similar careful handling to maintain their binding characteristics and functionality .

What experimental models are suitable for studying CD11d antibody therapeutic effects?

Researchers have successfully employed several experimental models to assess CD11d antibody therapeutic efficacy:

In vitro models:

• THP-1 monocytic cell line: This cell line can be differentiated with PMA (phorbol 12-myristate 13-acetate) to upregulate CD11d/CD18 expression, creating a reliable model for studying antibody binding dynamics and signaling effects .

• Primary human leukocytes: Both monocytes and neutrophils express CD11d and can be used to assess antibody binding characteristics through flow cytometry .

In vivo models:

• Rat spinal cord injury model: Clip compression injury at T4 has been successfully used to evaluate the therapeutic potential of CD11d antibodies. Key parameters measured include:

  • Myeloperoxidase (MPO) activity as a surrogate marker for neutrophil infiltration

  • BBB open-field locomotor assessment for functional recovery evaluation

  • Histological detection of leukocyte infiltration

  • ED-1 western blot macrophage detection

  • Myelin sparing post-injury

How can I determine the binding affinity and specificity of an anti-CD11d antibody?

Rigorous characterization of antibody binding properties is essential for research applications:

• Binding affinity determination:

  • Using PMA-differentiated THP-1 cells as an endogenous CD11d/CD18 model

  • Measuring the maximum binding (Bₘₐₓ) and dissociation constant (Kd)

  • For example, anti-CD11d-2 demonstrated a Bₘₐₓ of 85.5 ± 3.13% and a Kd of 3.55 × 10⁻¹¹ ± 0.872 × 10⁻¹¹ M

• Conformation-specific binding assessment:

  • Treatment with Mn²⁺ to force the active β2 integrin conformation

  • Treatment with EDTA to force the inactive confirmation

  • Comparison of binding under both conditions to determine conformation specificity

• Target specificity verification:

  • Testing binding on non-expressing cell lines (e.g., Jurkat T cells for CD11d) as negative controls

  • Comparing binding across different leukocyte subsets (e.g., monocyte subpopulations)

What flow cytometry protocols are recommended for detecting CD11d expression on different leukocyte populations?

Flow cytometry is a valuable tool for characterizing CD11d expression across leukocyte subsets:

• Sample preparation:

  • Isolate fresh primary human leukocytes or use established cell lines

  • Use appropriate buffer solutions to maintain cell viability and prevent non-specific binding

• Staining protocol:

  • Include markers to identify monocyte subsets (CD14, CD16) alongside CD11d antibodies

  • Include appropriate isotype controls to determine background staining levels

  • Consider using markers for activation status when analyzing expression

• Analysis strategies:

  • Quantify both percentage of positive cells and mean fluorescence intensity (MFI)

  • Compare expression across subpopulations (for example, nonclassical CD14+CD16+ monocytes exhibited the highest level of surface-expressed CD11d among monocyte subsets)

  • Analyze data using appropriate statistical methods to identify significant differences

How can I assess whether an antibody induces outside-in signaling upon binding to CD11d/CD18?

Antibody binding may potentially trigger signaling cascades, which can be beneficial or detrimental depending on research objectives:

• NF-κB activation assay:

  • Use reporter cell lines (e.g., THP-1 Luc2 cells) that express luciferase under NF-κB promoter control

  • Compare NF-κB expression following antibody treatment to positive controls (LPS, VCAM-1) and negative controls (isotype antibody, untreated wells)

  • Monitor expression over time (e.g., 24-hour period) to capture peak activation

• Tyrosine phosphorylation analysis:

  • Assess general tyrosine phosphorylation patterns and specific phosphorylation of key signaling proteins (e.g., FAK at Tyr397)

  • Stimulate cells with soluble antibody for defined time periods (e.g., 1 hour)

  • Use western blot analysis to quantify phosphorylation levels

  • Compare to appropriate controls to determine significance

• Functional consequence assessment:

  • Measure downstream cellular responses (adhesion, migration, cytokine production)

  • Correlate with signaling pathway activation to establish causality

For example, research on anti-CD11d-2 showed no significant difference in tyrosine phosphorylation or NF-κB activation compared to isotype controls, suggesting it does not induce inflammatory signaling upon binding .

What are the key differences between therapeutic applications of CD11c versus CD11d antibodies?

CD11c and CD11d antibodies have distinct therapeutic profiles based on their molecular targets and effects:

CD11c antibodies:

• Primarily used as research tools and diagnostic markers

• In pathological conditions, CD11c serves as a marker for hairy cell leukemia, acute non-lymphocytic leukemias, and some chronic lymphocytic leukemias

• Function as fibrinogen receptors involved in cell-cell interaction during inflammation

CD11d antibodies:

• Developed as potential immunomodulatory therapeutic agents

• Target specific pathophysiologies including neurotrauma, sepsis, and atherosclerosis

• Mechanism involves reducing leukocyte infiltration into affected tissues, particularly the central nervous system

• Provide neurological benefits by:

  • Reducing free radicals in the CNS

  • Decreasing oxidative/nitrosative damage

  • Increasing myelin sparing post-injury

  • Improving locomotor recovery in spinal cord injury models

What methodological approaches effectively demonstrate therapeutic efficacy of anti-CD11d antibodies in neurotrauma models?

A multi-faceted approach combining histological, biochemical, and functional assessments provides comprehensive evidence of therapeutic efficacy:

• Leukocyte infiltration measurement:

  • Myeloperoxidase (MPO) assay: Quantifies neutrophil infiltration in tissue homogenates

  • Histological detection: Visual confirmation of reduced leukocyte presence in affected tissues

  • ED-1 western blot: Specific detection of macrophage infiltration

• Tissue damage assessment:

  • Myelin sparing analysis: Quantifies preserved myelin following injury

  • Oxidative/nitrosative damage markers: Measures reduction in free radical-induced damage

• Functional recovery evaluation:

  • BBB open-field locomotor assessment: Gold standard for measuring recovery in rat SCI models

  • This approach revealed significantly higher BBB scores in anti-CD11d-3 treated rats compared to isotype controls, similar to results with the original mouse 217L antibody

• Comparative analysis:

  • Side-by-side comparison of humanized antibody clones with established murine antibodies

  • Statistical analysis to determine significant differences in outcomes between treatment groups

How do I interpret differences between total versus surface-level CD11d expression?

Research has uncovered interesting disparities between total and surface-level expression of CD11d/CD18:

• Expression mismatch phenomenon:

  • Using anti-CD11d-2 as a detection tool revealed a mismatch between total and surface-level CD11d and CD18 expression

  • This mismatch was not altered by CK2 inhibition in PMA-differentiated THP-1 cells

• Potential explanations:

  • Intracellular retention of CD11d/CD18 heterodimers

  • Regulation of surface transport mechanisms

  • Post-translational modifications affecting trafficking

• Methodological approach to investigate:

  • Compare flow cytometry (surface detection) with western blotting (total protein)

  • Use cell fractionation methods to isolate membrane versus cytoplasmic proteins

  • Employ immunofluorescence microscopy to visualize subcellular localization

• Research implications:

  • Experimental designs must consider potential differences between total and surface expression

  • Interpretation of knockout or inhibition studies should account for these differences

  • Therapeutic targeting strategies may need to consider both pools of protein

What factors should be considered when screening humanized antibody clones for preserved functionality?

When developing humanized antibodies from original murine clones, careful screening is essential to ensure therapeutic function is maintained:

• Binding characteristics assessment:

  • Flow cytometric analysis to determine percentage binding and mean fluorescence intensity

  • Comparison across different target cell populations (monocytes, neutrophils)

  • Testing for non-specific binding using non-expressing cell lines

• Functional screening approaches:

  • In vitro assays to measure expected cellular responses

  • In vivo models to assess therapeutic efficacy (e.g., rat SCI model)

  • Direct comparison with original murine antibody performance

• Key parameters to evaluate:

  • Neutrophil infiltration (MPO activity)

  • Behavioral/functional recovery (BBB locomotor scores)

  • Target engagement in relevant tissues

  • Minimal off-target effects

• Statistical considerations:

  • Appropriate sample sizes for detection of significant differences

  • Multiple comparison corrections when screening several antibody clones

  • Reproducibility across independent experiments

The successful humanization of anti-CD11d antibodies demonstrated that therapeutic benefits can be maintained while reducing immunogenicity, as shown by the preserved ability to improve neurological outcomes in rat models .

What are the emerging applications for CD11d-targeted therapeutics beyond neurotrauma?

Based on current research trends, CD11d-targeted therapeutics show promise in multiple areas:

• Sepsis management:

  • CD11d/CD18 targeting may modulate overwhelming immune responses in sepsis

  • Potential to reduce organ damage from excessive leukocyte infiltration

  • Could complement existing sepsis treatment approaches

• Atherosclerosis treatment:

  • Modulation of inflammatory processes in vascular disease

  • Potential reduction in plaque formation or progression

  • Integration with existing lipid-lowering therapies

• Broader inflammatory conditions:

  • The ability of anti-CD11d to reduce leukocyte infiltration could benefit various acute and chronic inflammatory conditions

  • Mechanistic focus on reducing oxidative/nitrosative damage is broadly applicable

What techniques can advance our understanding of CD11d/CD18 binding dynamics and epitope mapping?

Several advanced methodological approaches could further characterize CD11d/CD18 interactions:

• Structural analysis:

  • While no crystallized CD11d structure is currently available, computational models (e.g., AlphaFold) can predict structural features

  • The α7-helix, which elongates upon divalent cation binding to the MIDAS motif, is a key structural element

  • Epitope mapping techniques to precisely locate antibody binding sites on the CD11d I-domain

• Conformation-specific binding studies:

  • Comparison of binding in the presence of Mn²⁺ (active conformation) or EDTA (inactive conformation)

  • Analysis of binding to both peripheral blood leukocytes (inactive CD11d/CD18) and tissue-recruited leukocytes (active CD11d/CD18)

• Advanced imaging approaches:

  • Super-resolution microscopy to visualize integrin clustering and activation

  • FRET-based approaches to measure conformational changes in real-time

  • Single-molecule tracking to assess lateral mobility and complex formation

These approaches would significantly enhance our understanding of CD11d/CD18 biology and potentially lead to more targeted therapeutic strategies .