Anti-Human CD307e (FcRL5) [Clone 509F6] — Purified in vivo PLATINUM™ Functional Grade

Common In Vivo Applications of Clone 509F6 in Mice

Clone 509F6 is a mouse monoclonal antibody that specifically recognizes human FcRL5 (CD307e). While the search results provide robust detail about the antibody’s properties, immunogenicity, and in vitro uses, direct descriptions of in vivo applications of clone 509F6 in mice are not presented. However, insights can be drawn from the broader context and closely related research methodologies.

Antibody Characteristics

• Host: Mouse IgG2a.
• Target: Human FcRL5 (CD307e).
• Specificity: Does not cross-react with FcRL4; recognizes the first three Ig domains of human FcRL5.
• Purification: High purity, suitable for in vivo use when formulated specifically as “in vivo grade”.
• Formulation: Available in formats designed for preclinical in vivo studies.

In Vivo Applications (Inferred and Related)

No published studies directly describe 509F6 administration in mice for therapeutic or investigative purposes. However, the antibody is available in “in vivo grade” formulations, suggesting its potential suitability for animal studies where human FcRL5-expressing cells or xenografts are involved. Such antibodies are typically used when human proteins or cells are engrafted into immunodeficient mice (e.g., NSG, NOG, or other humanized mouse models).

Related Research Context

• Xenograft Models: Research using FcRL5 (CD307e) as a target often involves engrafting human tumor cells (e.g., multiple myeloma) into immunocompromised mice, followed by targeting with FcRL5-directed agents such as chimeric antigen receptor (CAR) T cells. While these studies use CAR-T cells rather than the 509F6 antibody itself, they demonstrate the relevance of the FcRL5 target in vivo.
• Functional Blockade: In vitro, clone 509F6 can block FcRL5 binding to IgG. If used in vivo, it could theoretically modulate B cell signaling or immune responses in models where human B cells or plasma cells are present.
• Flow Cytometry and Immunohistochemistry: In vivo applications may include detecting or tracking human FcRL5+ cells in mouse tissues after xenograft, although this is more common in ex vivo analysis rather than direct in vivo antibody administration.

Limitations

• No Direct Evidence: There is no published evidence in the provided search results of 509F6 being administered to mice for therapeutic, blocking, or depletion purposes.
• Species Reactivity: Clone 509F6 is specific for human FcRL5; it does not cross-react with mouse FcRL5, limiting its use to models involving human cells or proteins.
• In Vivo Grade Availability: The antibody is available in “in vivo grade” formats, but without explicit literature citations, its use in mice remains speculative.

Summary Table

Conclusion

Clone 509F6 is primarily used in research to detect or block human FcRL5 in vitro and in xenograft models involving human cells engrafted into immunodeficient mice. While “in vivo grade” formulations are available, there is no published evidence in the provided search results of its direct administration to mice for therapeutic or investigative purposes. Its in vivo applications would logically be limited to models where human FcRL5-expressing cells are present in mice, such as in oncology or immunology xenograft studies. For specific in vivo use cases, consultation of original research literature beyond these search results is recommended.

Commonly Used Antibodies and Proteins Paired with 509F6

509F6 is a monoclonal antibody specific for human CD307e (Fc receptor-like 5, FcRL5), primarily used for identifying and studying B cell subsets, especially in flow cytometry and related immunological assays. In the literature and commercial protocols, 509F6 is often combined with other B cell markers to enable detailed phenotypic analysis.

Standard B Cell Markers Used with 509F6

• CD19: Frequently used as a pan-B cell marker in flow cytometry, often conjugated to allophycocyanin (APC) for multiplex staining.
• CD27: A marker for memory B cells, commonly labeled with fluorescein isothiocyanate (FITC) and used alongside 509F6 to delineate naive vs. memory B cell populations.

These combinations allow researchers to sort and characterize different B cell subsets, especially in studies of normal and malignant B cell biology.

Additional Proteins and Antibodies in Functional Studies

• Immunoglobulins (Ig): FcRL5 (CD307e), targeted by 509F6, is known to bind to all IgG isotypes and plays a role in regulating immune complex interactions with B lymphocytes. Although IgG itself is not an antibody used for staining, its interaction with FcRL5 is central to functional studies, and 509F6 can block this interaction.
• CD21 and LAIR-1: While not directly paired with 509F6 in the provided sources, CD21 (complement receptor 2) and LAIR-1 (leukocyte-associated immunoglobulin-like receptor 1) are sometimes included in broader B cell phenotyping panels, and CD21 has been shown to form a receptor complex with FcRL5.
• SHP-1 phosphatase: FcRL5 recruits SHP-1 to its ITIM motifs, implicating SHP-1 in the inhibitory signaling pathway downstream of FcRL5 engagement. However, SHP-1 is generally studied in signaling contexts rather than as a co-staining target in flow cytometry.

Staining and Detection Considerations

When using 509F6 in flow cytometry, it is important to consider fluorochrome compatibility, especially if combining with other markers labeled with similar emission spectra (e.g., APC, Alexa Fluor® 700, or BD Horizon Red 718). Careful panel design is necessary to avoid spectral overlap and ensure accurate population identification.

Summary Table: Common Pairings with 509F6

Conclusion

In the literature and experimental protocols, 509F6 is most commonly paired with CD19 and CD27 antibodies for comprehensive B cell subset analysis via flow cytometry. Functional studies often explore the interaction between FcRL5 (targeted by 509F6) and IgG, as well as downstream signaling molecules like SHP-1. While other markers (e.g., CD21, LAIR-1) may be included in broader B cell phenotyping panels, CD19 and CD27 remain the most consistent and widely used partners for 509F6 in standard assays.

Clone 509F6, a monoclonal antibody targeting human FcRL5 (CD307e), has generated several important findings in B cell biology and hematologic malignancies research.

FcRL5 as a Biomarker in B Cell Malignancies

Research using clone 509F6 has identified FcRL5 as a significant biomarker in multiple B cell cancers. The antibody has been instrumental in demonstrating aberrant FCRL5 expression in multiple myeloma, chronic lymphocytic leukemia, mantle cell lymphoma, and hairy cell leukemia. High levels of soluble CD307e have been detected in the blood of patients with multiple myeloma, chronic lymphocytic leukemia, and mantle cell lymphoma. These findings suggest that FcRL5 may serve as both a diagnostic marker and potential therapeutic target for these malignancies.

Functional Characterization of FcRL5

Clone 509F6 has been critical in elucidating the molecular properties of FcRL5. The antibody recognizes an epitope within the first three immunoglobulin domains of FcRL5 and notably blocks FcRL5's interaction with immune complexes. Studies have shown that this antibody can block the binding of FcRL5 to all aggregated IgG isotypes. This blocking capability has been essential for understanding FcRL5's role as an IgG receptor that binds to all IgG isotypes, resulting in the inhibition of B cell receptor (BCR) signaling through the recruitment of SH2 domain-containing tyrosine phosphatase 1 (SHP-1) after tyrosine phosphorylation of its two immunoreceptor tyrosine-based inhibitory motifs (ITIMs).

Expression Patterns in B Cell Development

Clone 509F6 has enabled detailed mapping of FcRL5 expression across B cell differentiation stages. Research demonstrates that FcRL5 is differentially expressed in the B cell lineage, with little expression on peripheral blood cells and upregulated expression on plasma cells. The highest levels are found on naive and memory B cells and plasma cells, providing insights into the regulation of B cell function at different developmental stages.

Applications in Therapeutic Development

The characterization work performed with clone 509F6 has laid groundwork for therapeutic applications. Recent studies have explored anti-FcRL5 CAR-T cell therapy, demonstrating anti-multiple myeloma activity. The antibody's ability to specifically recognize FcRL5 on malignant B cells while understanding its normal expression pattern has proven valuable for developing targeted immunotherapies for B cell malignancies.

Dosing regimens for clone 509F6 (anti-human CD307e/FcRL5) in mouse models are not standardized, and detailed, peer-reviewed dosing protocols are limited in the available literature. Most sources specify its use primarily for in vitro applications, such as flow cytometry, immunoprecipitation, and blocking, with suggested dilutions (e.g., 5 µl per million cells per 100 µl for flow cytometry).

Key points based on available information:

• No universal in vivo dosing regimen: Protocols for in vivo mouse model dosing with clone 509F6 are not consistently published or agreed upon in the literature.
• Vendor recommendations focus on in vitro use: Main antibody suppliers (BioLegend, ThermoFisher, AffinityImmuno) provide quantities and volumes for flow cytometry and blocking studies but do not specify in vivo dosing schedules or amounts.
• Need for pilot studies: If using 509F6 in vivo, dosing will likely require pilot optimization based on experimental goals, delivery route, and antibody formulation, potentially using dosing ranges typical for other mouse antibodies (often 100–250 µg per mouse per injection), but this would be an inference rather than a documented standard.
• Literature searches may reveal isolated examples: Individual research studies may have used in vivo 509F6 dosing, but protocols would be study-specific and should be referenced directly if available.

In summary:
Dosing regimens of clone 509F6 across different mouse models are not standardized, and most protocols are tailored for in vitro assays; any in vivo use requires case-by-case optimization, and published protocols should be sought out or developed as appropriate for the specific experimental design.