SIRPB1 Antibody

What is SIRPB1 and what are its key biological functions?

SIRPB1 (Signal-Regulatory Protein Beta 1), also known as CD172b, is a member of the signal-regulatory-protein (SIRP) family and belongs to the immunoglobulin superfamily. It functions as a cell surface signaling receptor primarily expressed in leukocytes and the central nervous system .

Key biological functions include:

• Acts as a receptor-type transmembrane glycoprotein involved in the negative regulation of receptor tyrosine kinase-coupled signaling processes

• Interacts with TYROBP/DAP12, a protein bearing immunoreceptor tyrosine-based activation motifs

• Participates in the recruitment of tyrosine kinase SYK

• Regulates inflammatory factor expression in certain disease contexts, particularly in gliomas

• Modulates immune cell activation through SYK phosphorylation and subsequent activation of calcium, MAPK, and NF-κB signaling pathways

What are the recommended applications for SIRPB1 antibodies?

Based on validated research applications, SIRPB1 antibodies can be used in the following techniques:

Researchers should note that optimal dilutions may be sample-dependent and should be determined empirically for each experimental system .

What is the expression profile of SIRPB1 in normal and pathological tissues?

SIRPB1 expression patterns:

• Normal tissues: Primarily expressed in monocytes, macrophages, and dendritic cells

• Pathological contexts: Significantly upregulated in gliomas compared to normal brain tissue

• Cellular localization: Functions as an integral plasma membrane protein

Validation data from Human Protein Atlas projects have demonstrated SIRPB1 expression in various tissues through immunohistochemistry and immunofluorescence approaches .

Research has shown that SIRPB1 expression levels correlate with clinical parameters in gliomas, including WHO grade, IDH mutation status, and 1p/19q co-deletion status .

How can researchers effectively validate SIRPB1 antibody specificity?

Validating antibody specificity for SIRPB1 requires a multifaceted approach:

• Western blot verification:

  • Compare observed molecular weight (43 kDa) with the calculated molecular weight

  • Test in validated positive cell lines: U-937, A375, and PC-3 cells

  • Include SIRPB1 knockout controls generated using CRISPR/Cas9

• Cross-reactivity testing:

  • Be aware that some antibodies (e.g., OX130 MAb) can cross-react with other SIRP family members, particularly SIRPα

  • Validate in cells expressing different SIRP family members

  • Consider epitope mapping to determine regions specific to SIRPB1

• Genetic validation:

  • Use siRNA knockdown or CRISPR/Cas9 knockout models to confirm signal specificity

  • Prepare rescue experiments with ectopic expression of SIRPB1

• Isoform considerations:

  • Be aware that SIRPB1 has at least 3 identified isoforms

  • Check antibody recognition of specific isoforms, especially when working with isoform-specific antibodies

What methods are used to study SIRPB1 signaling in myeloid cells?

To investigate SIRPB1 signaling in myeloid cells, researchers employ several methodologies:

• Phosphorylation assays:

  • Monitor SYK phosphorylation following SIRPB1 activation with specific antibodies

  • Evaluate downstream targets including calcium signaling, MAPK, and NF-κB pathway activation

• Co-culture systems:

  • Establish co-cultures of macrophages with target cells (e.g., glioma cells)

  • Measure cytokine production (IL1RA, CCL2, IL-8) in response to SIRPB1 activation or inhibition

• Inhibitor studies:

  • Employ SYK inhibitors (e.g., GS9973) to validate the specificity of SIRPB1-mediated signaling

  • Compare responses between wild-type and SIRPB1 knockout macrophages

• Flow cytometry:

  • Use multi-parameter flow cytometry to analyze SIRPB1 expression alongside activation markers

  • Assess polarization states (M1/M2) of macrophages in relation to SIRPB1 expression

• CRISPR/Cas9 gene editing:

  • Generate SIRPB1 knockout THP-1 cell lines to study functional consequences

  • Validate knockouts using T7E1 digestion and Sanger sequencing

How does SIRPB1 contribute to tumor progression in gliomas?

SIRPB1's role in glioma progression has been elucidated through several research approaches:

• Expression analysis:

  • Analysis of 1152 normal samples from GTEx database and 670 glioma samples from TCGA revealed significantly higher SIRPB1 expression in gliomas

  • Higher expression correlates with poor patient survival

• Mechanistic studies:

  • SIRPB1 activation results in SYK phosphorylation and activation of calcium, MAPK, and NF-κB signaling pathways

  • This signaling cascade occurs primarily in myeloid-derived cells rather than glioma cells themselves

• Functional studies:

  • Macrophages with SIRPB1 knockout showed decreased production of IL1RA, CCL2, and IL-8

  • Cytokine production was restored when SIRPB1 was ectopically expressed

  • SYK inhibitor GS9973 reduced cytokine production, confirming pathway specificity

• Clinical correlations:

  • SIRPB1 expression correlates with WHO grade, IDH mutation status, and 1p/19q co-deletion status in gliomas

  • A prognostic model incorporating SIRPB1 expression and clinicopathological variables showed high prediction accuracy for patient outcomes

These findings suggest that SIRPB1 in tumor-associated macrophages contributes to an immunosuppressive tumor microenvironment, promoting glioma progression.

What are the technical challenges in developing SIRPB1 knockout models?

Researchers developing SIRPB1 knockout models face several technical challenges:

• Target specificity:

  • SIRP family members share sequence homology, requiring careful sgRNA design

  • Validation must confirm specific targeting of SIRPB1 without affecting other SIRP family members

• CRISPR/Cas9 design considerations:

  • For SIRPB1 targeting, optimal results have been achieved using sgRNAs designed for exon 1 (e.g., sgRNA1: 5ʹ-GAATGCCCGTGCCAGCCTCC-3ʹ, sgRNA2: 5ʹ-GGAGGCTGGCACGGGCATTC-3ʹ)

  • T7E1 digestion and Sanger sequencing are essential for validation

• Validation methods:

  • Western blot: Compare protein expression between wild-type and knockout cells

  • qPCR: Analyze mRNA expression levels

  • Functional assays: Assess pathway activation (particularly SYK phosphorylation)

• Single-cell cloning:

  • After transfection, dilute cells to 2 cells/ml and culture in 96-well plates for 21 days

  • Extract genomic DNA and verify via PCR with specific primers

  • Sanger sequencing to identify base deletions confirms successful editing

• Rescue experiments:

  • Generate synonymous mutant plasmids that are resistant to sgRNA targeting for rescue experiments

  • Include FLAG-tagged constructs for easy detection of exogenous protein

How can SIRPB1 antibodies be used to study inflammatory diseases?

SIRPB1 antibodies provide valuable tools for investigating inflammatory diseases through several approaches:

• Expression analysis in tissue samples:

  • Use immunohistochemistry to compare SIRPB1 expression between healthy and diseased tissues

  • Apply 1:200-1:500 dilutions for optimal staining in FFPE tissue sections

• Inflammatory pathway investigation:

  • Study NF-κB activation downstream of SIRPB1 in various inflammatory contexts

  • Assess cytokine production (IL-1, TNF-α, IL-6) using SIRPB1 activating or blocking antibodies

• Genetic variant studies:

  • Examine the impact of SIRPB1 variants on inflammatory signaling

  • For example, the c.1143_1144insG (p.Leu381_Leu382fs) frameshift variant is associated with Crohn's disease susceptibility

  • This variant induces tyrosine phosphorylation of Syk, Akt, and Jak2, elevates SIRPB1 expression, and promotes pro-inflammatory cytokine synthesis

• Co-culture systems:

  • Establish co-cultures of immune cells with tissue-specific cells

  • Assess the impact of SIRPB1 modulation on inflammatory responses

• Flow cytometry panels:

  • Design panels that include SIRPB1 alongside inflammatory markers

  • Analyze co-expression patterns in different immune cell populations

What are the optimal protocols for SIRPB1 immunohistochemistry in different tissue types?

For optimal SIRPB1 immunohistochemistry across different tissue types, researchers should consider the following protocol adaptations:

• Tissue preparation:

  • Use formalin-fixed paraffin-embedded (FFPE) tissue sections of 4 μm thickness

  • Consider antigen retrieval methods specific to each tissue type

• Antibody selection:

  • Choose antibodies validated for IHC applications

  • For human tissues, antibodies such as HPA047463 have been extensively validated in the Human Protein Atlas project

• Staining protocol adjustments:

  • For brain tissues: Extend primary antibody incubation times due to tissue density

  • For myeloid-rich tissues: Background issues may require additional blocking steps

  • For xenograft models: Verify species reactivity of the antibody (human vs. mouse)

• Automated staining systems:

  • BenchMark XT automated tissue staining systems have been successfully used for SIRPB1 IHC

  • Follow manufacturer's validated protocols with appropriate optimization

• Validation controls:

  • Include SIRPB1-high tissues (U-937 cells, A375 cells, PC-3 cells) as positive controls

  • SIRPB1-knockout tissues or cells serve as negative controls

  • Consider including multiple antibodies targeting different epitopes for validation

How can researchers investigate SIRPB1's role in cancer progression beyond gliomas?

While SIRPB1's role is well-established in gliomas, researchers can apply similar methodologies to investigate its function in other cancer types:

• Expression analysis in multiple cancer types:

  • Analyze TCGA data for SIRPB1 expression across different cancers

  • Research indicates SIRPB1 may impact prognosis in kidney renal clear cell carcinoma and skin cutaneous melanoma differently than in gliomas

• Copy number variation studies:

  • Investigate SIRPB1 gene amplification, which has been detected in up to 37.5% of prostate cancer specimens

  • Utilize FISH and laser capture microdissection coupled with qPCR for this purpose

• Functional studies in prostate cancer:

  • SIRPB1 knockdown in PC3 prostate cancer cells suppresses cell growth and mobility

  • SIRPB1 overexpression in C4-2 prostate cancer cells enhances migration, invasion, colony formation, and xenograft tumor take rate

• Signaling pathway investigation:

  • SIRPB1 regulates Akt phosphorylation in prostate cancer cells

  • Akt inhibition abolishes SIRPB1 stimulation of prostate cancer cell proliferation

• Hormone response studies:

  • In prostate cancer, evaluate whether SIRPB1 expression is androgen-responsive

  • C4-2 cells can be stimulated with dihydrotestosterone (DHT) to determine whether SIRPB1 expression is sensitive to androgens

What are the common technical issues when using SIRPB1 antibodies and how can they be resolved?

Researchers may encounter several technical challenges when working with SIRPB1 antibodies:

• Cross-reactivity with other SIRP family members:

  • Issue: Some antibodies (e.g., OX130 MAb) recognize both SIRPB1 and certain SIRPα alleles

  • Solution: Validate antibody specificity using cells expressing individual SIRP family members

  • Methodological approach: Include SIRPα-expressing controls in experiments

• Variable results across different samples:

  • Issue: SIRP family members are relatively polymorphic

  • Solution: When possible, genotype samples for SIRP variants

  • Methodological approach: Include multiple donor samples when working with primary cells

• Signal detection problems in Western blot:

  • Issue: Weak or nonspecific bands

  • Solution: Optimize antibody dilution (1:500-1:2000 recommended for most SIRPB1 antibodies)

  • Methodological approach: Use validated positive control cell lines (U-937, A375, PC-3 cells)

• Background in immunohistochemistry:

  • Issue: High background in myeloid-rich tissues

  • Solution: Additional blocking steps and optimization of antibody concentration

  • Methodological approach: Include Fc receptor blocking solution before antibody incubation

• Antibody storage issues:

  • Issue: Loss of activity over time

  • Solution: Store at -20°C in aliquots to avoid freeze-thaw cycles

  • Methodological approach: Follow manufacturer's storage recommendations (most SIRPB1 antibodies are stable for one year when properly stored)

How can researchers verify the specificity of SIRPB1 antibodies across different experimental systems?

Ensuring antibody specificity across different experimental systems requires a comprehensive validation approach:

• Multi-technique validation:

  • Compare results across different techniques (WB, IHC, flow cytometry)

  • Consistent detection at the expected molecular weight (43 kDa) across techniques supports specificity

• Genetic approaches:

  • Employ siRNA or CRISPR/Cas9-based knockdown/knockout models

  • Verify reduced or absent signal in genetically modified cells

  • Include rescue experiments with ectopic expression of SIRPB1

• Epitope blocking:

  • Pre-incubate antibody with immunizing peptide

  • Specific signal should be blocked when the antibody is neutralized by its target epitope

• Protein array screening:

  • Some SIRPB1 antibodies have been validated against protein arrays of 364 human recombinant protein fragments

  • This approach identifies potential cross-reactivity with unrelated proteins

• Multiple antibody comparison:

  • Use antibodies targeting different epitopes of SIRPB1

  • Consistent results across different antibodies increase confidence in specificity

  • Consider antibodies targeting AA 30-371, AA 30-206 (Isoform 3), AA 17-43 (N-Term), AA 127-356, or AA 107-134 regions

What are the best practices for quantifying SIRPB1 expression in complex tissue samples?

Quantifying SIRPB1 expression in complex tissues requires careful methodological considerations:

• Tissue microdissection approaches:

  • Laser capture microdissection can isolate specific cell populations from heterogeneous tissues

  • RNA isolation, reverse transcription, and qPCR can then be performed using CellsDirect One-Step qRT-PCR Kit

  • Design gene-specific primers and Taqman probes that cross exon/exon junctions

• Single-cell analysis:

  • Single-cell RNA sequencing can identify cell types expressing SIRPB1

  • Analyze datasets focused on specific diseases (e.g., astrocytoma and glioblastoma single-cell datasets)

  • Use tools like Single Cell Portal to examine SIRPB1 expression across different cell types

• Immunohistochemistry quantification:

  • Use digital pathology software for quantitative analysis

  • Consider H-score method (intensity × percentage of positive cells)

  • For multiplex IHC, analyze co-localization with cell-type specific markers

• Flow cytometry approaches:

  • Design panels with SIRPB1 and lineage markers

  • Example panel: FITC-anti-CD11b, APC-anti-CD206, PE-anti-CD86, and anti-SIRPB1

  • Gate on specific cell populations before quantifying SIRPB1 expression

• RNA-seq analysis:

  • For bulk RNA-seq, computational deconvolution can estimate cell-type specific expression

  • ssGSEA approach with GSVA package can assess immune infiltration in relation to SIRPB1 expression

How is SIRPB1 being investigated as a potential therapeutic target in cancer and inflammatory diseases?

SIRPB1 is emerging as a promising therapeutic target with several investigational approaches:

• Targeting SIRPB1 in gliomas:

  • Research suggests SIRPB1 could serve as a therapeutic target for gliomas by modulating the tumor microenvironment

  • Blocking SIRPB1-mediated signaling may reduce the production of tumor-promoting cytokines (IL1RA, CCL2, IL-8)

• SYK inhibitor approaches:

  • SYK inhibitors like GS9973 can block downstream signaling from SIRPB1

  • This approach may be particularly effective in targeting myeloid cells within the tumor microenvironment

• Antibody-based therapeutics:

  • Development of blocking antibodies that specifically target SIRPB1 without cross-reactivity to other SIRP family members

  • Such antibodies could modulate macrophage polarization in the tumor microenvironment

• Inflammatory disease applications:

  • The association of SIRPB1 variants with Crohn's disease suggests potential in inflammatory bowel disease therapy

  • Targeting the DAP12-SIRPB1 signaling axis may modulate inflammatory responses

• Combination therapy strategies:

  • Combining SIRPB1 targeting with immune checkpoint inhibitors may enhance anti-tumor immunity

  • Dual targeting of SIRPB1 and SIRPα pathways is being explored in preclinical models

What are the newest techniques for studying SIRPB1-mediated signaling pathways?

Research on SIRPB1 signaling is advancing with several cutting-edge techniques:

• CRISPR activation/inhibition systems:

  • CRISPRa/CRISPRi approaches allow modulation of SIRPB1 expression without genetic modification

  • This enables temporal control and dose-dependent studies of SIRPB1 function

• Phosphoproteomics:

  • Mass spectrometry-based phosphoproteomics can identify the complete signaling network downstream of SIRPB1

  • This approach has revealed SIRPB1 activation leads to phosphorylation of Syk, Akt, and Jak2

• Live-cell imaging:

  • FRET-based biosensors can monitor SIRPB1-mediated signaling in real-time

  • This allows dynamic assessment of calcium signaling, MAPK activation, and NF-κB translocation

• Single-cell multi-omics:

  • Integration of scRNA-seq with scATAC-seq or CyTOF provides comprehensive understanding of SIRPB1 function

  • This approach can reveal how SIRPB1 signaling affects gene expression programs and cellular phenotypes

• Organoid models:

  • Patient-derived organoids incorporating immune components can model SIRPB1 function in a physiologically relevant context

  • Co-culture systems with organoids and immune cells allow study of SIRPB1 in tissue-specific microenvironments

How do SIRPB1 genetic variants impact immune regulation and disease susceptibility?

Research on SIRPB1 genetic variants has revealed important insights into immune regulation and disease:

• Frameshift variant in Crohn's disease:

  • The c.1143_1144insG (p.Leu381_Leu382fs) frameshift variant is associated with increased susceptibility to Crohn's disease in Han Chinese patients (OR 4.59)

  • This gain-of-function variant enhances tyrosine phosphorylation of signaling molecules and promotes pro-inflammatory cytokine production

• Copy number variations in cancer:

  • SIRPB1 gene amplification has been detected in up to 37.5% of prostate cancer specimens

  • Copy number variations correlate with increased SIRPB1 expression and enhanced cancer cell proliferation

• Polymorphisms affecting immune function:

  • SIRPB1 copy-number polymorphism has been associated with impulsive-disinhibited personality traits

  • Research in type 1 diabetes suggests dysregulated SIRP:CD47 signaling may affect lymphocyte activation and cytotoxicity

• Methodological approaches to study variants:

  • CRISPR/Cas9 gene editing to introduce specific variants

  • Patient-derived cells carrying natural variants

  • Transgenic expression of variant SIRPB1 in cell lines or animal models

  • Computational analysis of variant effects on protein structure and function

Understanding these genetic variants provides insights into personalized therapeutic approaches targeting the SIRPB1 pathway in different patient populations.