Anti-Mouse/Human PNAd (Clone MECA-79) – Purified in vivo GOLD^TM Functional Grade

Common in vivo applications of clone MECA-79 in mice include blocking L-selectin–dependent lymphocyte homing to peripheral lymph nodes, detecting and characterizing high endothelial venules (HEVs) in lymphoid tissues and sites of chronic inflammation, and studying immune cell trafficking.

MECA-79 is a rat monoclonal antibody that recognizes the peripheral node addressin (PNAd) carbohydrate epitope, prominently expressed on HEVs. In vivo uses are centered on:

• Functional Blockade Experiments: MECA-79 is frequently injected into mice to block lymphocyte homing to peripheral lymph nodes by inhibiting the interaction between PNAd on HEVs and L-selectin on lymphocytes. This helps dissect the molecular basis of lymphocyte trafficking and HEV function.
• Disease Models: The antibody is used to study HEV-like vessels induced in sites of chronic inflammation, such as autoimmune disease models (e.g., diabetes in NOD mice, rheumatoid arthritis). MECA-79 staining identifies newly formed HEVs at inflamed tissues, enabling studies on tissue-specific immune responses.
• Therapeutic Delivery: Conjugated MECA-79 has been used to target drugs or nanoparticles specifically to draining lymph nodes or inflamed tissues expressing PNAd, leveraging HEV-specific accumulation for therapeutic effect.
• Developmental and Genetic Studies: Transgenic mice using MECA-79-reactive promoters or antigen detection allow assessment of gene targeting in HEVs and PNAd+ tissues to study how these vessels mature and respond to environmental cues or genetic manipulation.

Additional applications include:

• Immunohistochemical in vivo staining to map PNAd distribution and HEV presence in mouse organs and pathological tissues.
• Used as a marker to differentiate mature HEVs (MECA-79+) from immature ones (MECA-367+), helping clarify lymphoid tissue development and immune cell entry points.

In summary, MECA-79 is a well-established tool for in vivo blockade of lymphocyte homing, mapping and manipulation of HEVs in lymphoid and inflamed tissues, and facilitating targeted delivery or gene targeting studies in mouse models.

Commonly used antibodies or proteins with MECA-79 in the literature typically include those that help characterize immune cell types, lymphoid tissue markers, or endothelial structures, either as co-staining partners in immunohistochemistry/flow cytometry or as functional comparators. Key examples are:

• CD3 and CD28: Used for T cell activation assays; these antibodies are standard for stimulating and assessing T cell function in studies where MECA-79 is applied to track trafficking or immune modulation.
• CD62L (L-selectin): MECA-79 blocks L-selectin-dependent lymphocyte emigration and adhesion, making CD62L a frequent co-marker when studying lymphocyte-HEV interactions.
• IgM: Used as a marker for B cells, notably in dual staining protocols to distinguish MECA-79^+ B cells (especially in Peyer’s patches, appendix, and spleen).
• GlyCAM-1 and CD34: Both are ligands for L-selectin and recognized by MECA-79, and are often characterized alongside MECA-79 when investigating HEV biology.
• MECA-367: Another HEV-specific antibody sometimes used in parallel or comparison with MECA-79 to distinguish addressin isoforms and tissue distribution.
• Endothelial markers and general immune cell markers: These may include pan-leukocyte antibodies, further endothelial structure markers (like von Willebrand factor), or activation/infiltration markers in studies of inflammation and tumor vasculature.

Summary Table: Common Markers Used with MECA-79

These antibodies and proteins are chosen based on the research context—whether the focus is on lymphocyte trafficking, HEV identification, immune modulation, or tissue characterization. When designing multiplex immunohistochemistry panels or flow cytometry experiments with MECA-79, select antibodies that clarify the cell types, addressins, or functional pathways of interest.

Clone MECA-79 is a monoclonal antibody widely cited for its critical role in immunology, particularly in identifying and characterizing high endothelial venules (HEVs) and trafficking of lymphocytes. Key findings from MECA-79-cited literature include:

• MECA-79 defines “peripheral node addressin” (PNAd): MECA-79 reacts with a complex of glycoproteins on HEVs, collectively called PNAd, which serve as L-selectin ligands facilitating lymphocyte homing to lymph nodes.

• Epitope specification: The MECA-79 epitope is a sulfated carbohydrate moiety, specifically involving the GlcNAc-6-sulfate modification. Importantly, its recognition is independent of sialylation and fucosylation, distinguishing it from other selectin ligands.

• Broad species reactivity: MECA-79 labels HEVs in both mouse and human tissues, highlighting its utility in cross-species lymph node studies.

• Functional blockade of lymphocyte trafficking: MECA-79 functionally blocks L-selectin-mediated binding of lymphocytes to HEVs, demonstrating its use in studying lymphocyte recruitment and immune response regulation.

• Protein targets: The MECA-79 epitope decorates multiple glycoproteins, including CD34, podocalyxin, and endomucin, which have been identified as major components of PNAd in human tissues.

• Applications in targeted drug delivery: Leveraging MECA-79’s specificity, researchers have conjugated immunosuppressive drugs to MECA-79-coated microparticles. This enables targeted accumulation and immune modulation within draining lymph nodes, prolonging allograft survival and significantly reducing systemic drug exposure in transplant models.

• Tumor HEV studies: MECA-79 staining is used to identify HEVs within tumor environments, correlating HEV density with immune cell recruitment and, in some studies, with clinical outcomes such as tumor microsatellite instability.

• Endothelial cell characterization: Loss of MECA-79 expression is associated with dedifferentiation of HEV endothelial cells outside their physiological context, underscoring its importance as a marker of specialized endothelial differentiation.

These findings illustrate that MECA-79 is indispensable for:

• Distinguishing HEVs and their unique glycosylation patterns.
• Interrogating lymphocyte trafficking mechanisms.
• Designing targeted immune therapies.
• Investigating immune cell recruitment in diseases including cancer and transplantation.

MECA-79’s epitope mapping, protein associations, and functional blockade capacity make it a cornerstone reagent in vascular immunology research.

Dosing regimens of the antibody clone MECA-79 vary substantially across mouse models depending on the experimental goal—such as functional blockade, targeting, or mechanistic studies. However, published literature provides limited detailed dosing schedules compared to other more commonly used immunomodulatory antibodies.

Key findings from the available sources:

• In functional targeting and drug-delivery contexts, MECA-79 is most often used conjugated to nanoparticles or microparticles, rather than as a standalone injectable antibody, making direct dosing comparisons difficult.
• When used as a blocking antibody (for example, to inhibit L-selectin-dependent lymphocyte adhesion via PNAd), MECA-79 is reported to be effective both in vitro and in vivo, but standard dosing amounts (e.g., μg per mouse) are typically not specified in commercial or literature summaries.

Dosing in Specific Mouse Models

Context and Interpretation

• Route of Administration: Most physiological/therapeutic experiments favor intravenous injection (to target vascular HEVs).
• Functional vs. Labeling Use: In vivo blocking or targeting may use higher doses than ex vivo histology or flow cytometry applications; for reference, many functional antibody blockade studies in mice use 50–250 μg/dose, 1–3 times per week, but this is an extrapolation from other antibody clones rather than MECA-79-specific published data.
• Conjugated Formulation: In most recent literature, MECA-79’s primary use is as a targeting moiety on drug/nanoparticle carriers, with dosing described in terms of carrier particle amount, not unmodified antibody.
• Commercial Guidance: Most product sheets and distributor databases do not specify an optimal in vivo dosing regimen for MECA-79, highlighting the need to consult individual primary literature for model-specific protocols.

In summary:
There are no universally standardized dosing regimens for clone MECA-79 across mouse models, with dosing most commonly determined empirically by experimental endpoint and whether the antibody is delivered unconjugated or attached to a carrier. Extrapolation from other in vivo blocking antibodies suggests a range of 50–250 μg/mouse/dose as typical, but for MECA-79, especially in drug-delivery studies, the effective dose is better defined by functional outcome than by antibody amount alone.