Recombinant Macaca mulatta C-X-C chemokine receptor type 6 (CXCR6)

What is the amino acid sequence of Macaca mulatta CXCR6 and how does it compare to human CXCR6?

Recombinant Macaca mulatta CXCR6 consists of 343 amino acids with the sequence: MAEYDHYEDDGFLNSFNDSSQEEHQDFLQFRKVFLPCMYLVVFVCGLVGNSLVLVISIFYHKLQSLTDVFLVNLPLADLVFVCTLPFWAYAGIHEEWIFGQVMCKTLLGVYTINFYTSMLILTCITVDRFIVVVKATKAYNQQAKRMTWGKVICLLIWVISLLVSLPQIIYGNVFNLDKLICGYHDEEISTVVLATQMTLGFFLPLLAMIVCYSVIIKTLLHAGGFQKHRSLKIIFLVMAVFLLTQTPFNLVKLIRSTHWEYYAMTSFHYTIIVTEAIAYLRACLNPVLYAFVSLKFRKNFWKLVKDIGCLPYLGVSHQWKSSEDNSKTFSASHNVEATSMFQL .

The protein is characterized by seven transmembrane domains typical of G-protein coupled receptors, with key functional regions including the N-terminal domain involved in ligand binding and intracellular domains mediating signal transduction. While human and rhesus macaque CXCR6 share high sequence homology, researchers should note species-specific differences in post-translational modifications that may affect antibody recognition and functional studies.

What cellular distribution patterns are observed for CXCR6 in Macaca mulatta immune tissues?

CXCR6 expression in Macaca mulatta follows tissue-specific and activation-dependent patterns, primarily observed on lymphocyte subsets. Research protocols for characterizing CXCR6 distribution should include:

• Multi-parameter flow cytometry using anti-CXCR6 antibodies (such as PE-conjugated clone 56811) validated for cross-reactivity with Macaca mulatta

• Tissue immunohistochemistry with appropriate controls

• Single-cell RNA sequencing to detect CXCR6 transcripts across immune populations

CXCR6 is predominantly expressed on activated CD8+ T cells, particularly those with tissue-resident memory (TRM) phenotypes. During inflammatory conditions, increased percentages of CD8+CXCR6+ cells are observed in affected tissues, with studies showing up to 60% of liver-infiltrating CD8+ T cells expressing high levels of CXCR6 during inflammation compared to 24% in non-inflammatory conditions .

How does CXCR6 contribute to T cell migration and tissue residency in Macaca mulatta models?

CXCR6 plays a critical role in directing CD8+ T cell migration to specific tissue microenvironments through interaction with its ligand CXCL16. To investigate this function:

• Perform short-term (6-hour) cell migration assays using CXCR6+ and CXCR6-deficient cells to quantify tissue-specific recruitment

• Utilize Transwell migration systems with optimal concentrations of CXCL16 chemokine

• Include internal standards (such as polystyrene beads) to calculate accurate migration percentages

Studies demonstrate that CXCR6-deficient CD8+ T cells show approximately 33% reduction in liver localization during inflammatory conditions, while maintaining normal blood frequencies . This indicates CXCR6's specific role in tissue-directed migration rather than general circulation.

The mechanism involves both chemotactic signaling and adhesion functions. CXCR6-CXCL16 interaction creates a distinct perivascular niche populated by CCR7+ dendritic cells (specifically DC3) that express membrane-bound CXCL16 and trans-present IL-15 . This interaction promotes the formation of a synaptic complex essential for T cell tissue residency and survival.

What methodologies are recommended for studying CXCR6-dependent CD8+ T cell recruitment in tissue inflammation models?

For investigating CXCR6-dependent CD8+ T cell recruitment in Macaca mulatta inflammation models, researchers should implement:

• Congenic transfer system: Use Thy1.1/Thy1.2 or comparable congenic markers to distinguish transferred cell populations

• Sequential transfer protocol:

  • First transfer: Establish inflammatory condition

  • Second transfer: Introduce CXCR6+ or CXCR6-deficient cells

  • Analysis: Compare recruitment after defined time window (6 hours optimal)

• Multiparameter analysis: Simultaneously assess:

  • Recruitment (using congenic markers)

  • Proliferation (Ki-67 or CFSE dilution)

  • Apoptosis (Annexin V/7-AAD staining)

This comprehensive approach distinguishes recruitment defects from altered proliferation or survival. In graft-versus-host disease models, CXCR6-deficient CD8+ cells showed specific recruitment deficits to liver without altered proliferation or apoptosis rates , demonstrating the selective contribution of CXCR6 to tissue localization.

How does CXCR6 expression influence tumor infiltration by CD8+ T cells in macaque cancer models?

CXCR6 expression on CD8+ T cells significantly enhances their tumor-infiltrating capacity through several mechanisms:

• Positioning within specialized tumor niches: CXCR6+ CD8+ T cells localize to perivascular regions populated by DC3 dendritic cells expressing CXCL16

• Enhanced survival in tumor microenvironment: The interaction between CXCR6+ CD8+ T cells and DC3 cells creates a survival niche through IL-15 trans-presentation, preventing activation-induced cell death

• Radiation-enhanced recruitment: Ionizing radiation increases CXCL16 expression in tumor cells across multiple cancer types, potentially enhancing CXCR6-dependent T cell infiltration

Experimental approaches to study this phenomenon should include:

• Flow cytometric analysis comparing CXCR6+ versus CXCR6- T cell tumor infiltration

• Adoptive transfer studies with tracking of congenic markers

• Combinatorial therapy models incorporating radiation and CXCR6+ T cell transfer

Research has shown that CXCR6-deficient CAR-T cells demonstrate poorer tumor infiltration compared to wild-type counterparts, highlighting the receptor's role in therapeutic T cell targeting .

What is the role of CXCR6 in vaccine-induced immunity in macaque models, and how can it be experimentally evaluated?

CXCR6 plays a critical role in vaccine-induced immunity, particularly for establishing tissue-resident memory responses. Key findings include:

• CXCR6 is preferentially expressed by CD8+ TRM cells following vaccination in mice and is similarly enriched on intratumoral CD8+ TRM cells from human lung cancer

• Vaccination of CXCR6-deficient animals results in defective lung recruitment of antigen-specific CD8+ T cells, particularly affecting TRM subsets

• Route of administration significantly impacts CXCR6-dependent responses: intranasal vaccination induces higher and more sustained CXCL16 concentrations in pulmonary tissues compared to intramuscular delivery

For comprehensive evaluation of CXCR6's role in vaccine responses, implement:

• Comparative vaccination protocols:

  • Compare intranasal versus intramuscular routes

  • Track kinetics of CXCL16 expression in target tissues

  • Measure frequencies of CXCR6+ antigen-specific T cells

• Challenge studies:

  • Evaluate protection against tumor challenge in CXCR6-sufficient versus CXCR6-deficient contexts

  • Analyze correlation between CXCR6+ TRM frequencies and protection metrics

• Adjuvant assessment:

  • Test adjuvants known to enhance TRM formation (IL-15, 4-1BBL, Notch inhibitors) for their capacity to induce CXCR6 expression

What flow cytometry protocols are optimal for detecting CXCR6 expression on Macaca mulatta lymphocytes?

For accurate detection of CXCR6 on Macaca mulatta lymphocytes, the following optimized protocol is recommended:

• Antibody selection: PE-conjugated anti-CXCR6 antibody (clone 56811) has been validated for primate samples including Macaca mulatta

• Sample preparation:

  • Use freshly isolated cells when possible

  • For tissue-resident cells, optimize tissue digestion protocols to preserve surface receptor expression

  • Include viability dye to exclude dead cells that often display non-specific binding

• Staining protocol:

  • Perform surface staining at 4°C to prevent receptor internalization

  • Use optimal antibody dilutions determined through titration experiments

  • Include appropriate isotype controls for accurate gating

• Analysis considerations:

  • Implement multi-parameter analysis including lineage markers (CD3, CD8), activation markers (CD69, CD103), and CXCR6

  • Use fluorescence-minus-one (FMO) controls for setting CXCR6 positivity thresholds

  • Consider density plots rather than histograms for better visualization of CXCR6 distribution

When analyzing tumor-infiltrating lymphocytes, researchers should distinguish CXCR6 and CXCL16 co-expressing populations, as demonstrated in lung cancer cell line studies where up to 82.9% of SCC cells expressed both receptor and ligand .

How can CXCR6 function be effectively studied in Macaca mulatta in vitro systems?

To investigate CXCR6 functionality in Macaca mulatta cells, researchers should employ these methodological approaches:

• Migration assays:

  • Transwell systems with 5-μm pore size inserts

  • Optimal CXCL16 concentration determined through dose-response experiments

  • 2-hour migration period at 37°C

  • Addition of polystyrene beads as internal standard for quantification

  • Flow cytometric analysis of migrated versus input populations

• Functional readouts:

  • Calcium flux assays following receptor stimulation

  • Phosphorylation of downstream signaling molecules (ERK, AKT)

  • Cytokine production and receptor internalization kinetics

• Comparative analysis:

  • Side-by-side comparison with human CXCR6 to identify species-specific differences

  • Heterologous expression systems using both receptors in identical cellular backgrounds

  • Pharmacological inhibitor studies to dissect signaling pathways

When conducting these assays, controls should include cells from CXCR6-deficient animals or CXCR6-blocked cells to confirm specificity of observed effects .

How does CXCR6 function as a coreceptor for SIV in Macaca mulatta models, and what experimental approaches best characterize this interaction?

CXCR6 serves as an important coreceptor for SIV infection in non-human primate models, with significant implications for understanding viral pathogenesis:

• CXCR6 is a major coreceptor for SIV in natural hosts like sooty mangabeys and African green monkeys, particularly in species that express low levels of the canonical CCR5 coreceptor

• To characterize CXCR6-mediated SIV entry in Macaca mulatta models, researchers should implement:

  • Viral entry assays: Compare infection efficiency in cells expressing or lacking CXCR6

  • Coreceptor tropism analysis: Use pseudotyped viruses with various envelope proteins to assess CXCR6 utilization

  • Inhibition studies: Test blocking antibodies or small molecule inhibitors targeting CXCR6

  • Genetic association studies: Correlate CXCR6 polymorphisms with infection outcomes

• Comparative analysis between pathogenic (SIVmac in rhesus macaques) and non-pathogenic SIV infections indicates differences in coreceptor usage patterns, with potential significance for disease progression

This research direction provides valuable insights into the evolutionary relationships between SIV strains and their host adaptations, potentially informing HIV therapeutic strategies.

What is the ambivalent role of CXCR6+ T cells in tumor control, and how can this be investigated in macaque models?

CXCR6+ T cells demonstrate context-dependent roles in tumor immunity that warrant careful experimental investigation:

• Beneficial anti-tumor functions:

  • CXCR6+ CD8+ T cells with resident phenotype contribute to control of primary tumor proliferation and metastasis in multiple models

  • They establish critical interactions with CXCL16-expressing DC3 dendritic cells that sustain their survival through IL-15 trans-presentation

• Potentially harmful inflammatory functions:

  • In models of chronic inflammation such as NASH, CXCR6+P2X7+ T cells can destroy hepatocytes in a non-MHC-restricted manner

  • This activity distinguishes them from classical CD8+ TRM cells and represents a separate functional pathway

To investigate this duality in macaque models, researchers should:

• Design studies comparing CXCR6+ T cell function in:

  • Acute versus chronic inflammation models

  • Different tissue microenvironments (liver versus lung)

  • Various cancer types with distinct inflammatory profiles

• Characterize CXCR6+ subpopulations through:

  • Co-expression analysis of additional markers (P2X7, PD-1, TIM-3)

  • Transcriptomic profiling to identify signature gene programs

  • Functional assays measuring both antigen-specific and non-specific cytotoxicity

Understanding this functional dichotomy is critical for developing targeted immunotherapies that enhance beneficial CXCR6-dependent tumor control while minimizing potential inflammatory damage.