Anti-Mouse CD19 [Clone 1D3] — Purified in vivo GOLD™ Functional Grade

Clone 1D3 is a rat IgG2a monoclonal antibody that specifically targets mouse CD19, a B cell-specific surface marker. This antibody has several important in vivo applications in mouse models:

B Cell Depletion Studies

Clone 1D3 is used for in vivo B cell depletion experiments, though it often requires combination with other antibodies such as anti-mouse B220 (clone RA3) to achieve complete B cell depletion. The antibody has been shown to successfully eliminate both normal B cells and B cell lymphomas in treated mice, with the only observed toxicity being a lack of B cells.

CAR T Cell Development

A major application of clone 1D3 is as the antigen-binding domain for constructing mouse-specific anti-CD19 chimeric antigen receptor (CAR) T cells. The variable regions from the 1D3 hybridoma have been cloned and incorporated into CAR constructs, such as 1D3-28Z, which combines the 1D3 antibody sequences with CD28 costimulatory and CD3-ζ signaling domains. These CAR T cells have demonstrated effective antilymphoma activity in preclinical mouse models, with treated mice surviving without signs of lymphoma or toxicity for extended periods up to 8 months.

Switch-Based CAR T Systems

The 1D3 antibody has been adapted to create switchable CAR T cell systems. The Fab fragment (lacking the Fc domain) of clone 1D3 has been used to develop anti-murine CD19 switches that allow for controlled CAR T cell expansion and B cell depletion. This approach enables researchers to toggle CAR T cell activity on and off by administering or withholding the switch molecule.

Functional Assays

Clone 1D3 is utilized in various functional assays including bioanalytical pharmacokinetic (PK) and anti-drug antibody (ADA) assays, as well as studies examining biological mechanisms. It can also be used for in vivo CD19 neutralization experiments.

Commonly, anti-mouse CD19 antibody clone 1D3 is used in combination with other antibodies that target B-cell surface markers or related proteins in immunological research. The most frequently paired antibodies or proteins include:

• Anti-mouse B220 (clone RA3-6B2): Used to identify pan-B cell populations alongside CD19.
• Anti-mouse CD22 (clone Cy34.1): CD22 is another B cell marker often examined with CD19 to study B cell biology.
• CD21 and CD81: These proteins form a co-receptor complex with CD19 as part of the B cell receptor (BCR) signaling machinery and are often analyzed simultaneously for B cell characterization.
• MHC class II, Leu13: Part of the broader signaling complexes assessed in B cell studies together with CD19.
• CD3: While not directly paired with CD19 for B cell characterization, multispecific antibodies (such as BiTEs) sometimes include anti-CD19 and anti-CD3 components for therapeutic applications.

Additional antibodies frequently combined in B cell immunophenotyping panels include, but are not limited to:

• Anti-CD45R (B220 specifically)
• Anti-IgM, Anti-IgD (to delineate stages of B cell maturation)

Where depletion or functional analysis is required, combinations like 1D3 with RA3-6B2 (B220) have been reported to be more effective in depleting B cells compared to 1D3 alone.

These selections allow for comprehensive analysis of B cell subsets, differentiation states, and functional properties in mouse models. The use of these marker combinations is established in flow cytometry, immunoprecipitation, and immunohistology applications.

Clone 1D3 is a monoclonal antibody extensively cited in scientific literature as a tool for detecting and manipulating mouse CD19, a B cell–specific surface antigen. The primary key findings from its use are:

• B cell Identification and Quantification: 1D3 is a gold-standard reagent for the identification and quantification of B cells in mice by flow cytometry, immunohistochemistry, and related methods. CD19 is expressed across all developmental stages of B cells, and 1D3 binds specifically to this protein, enabling researchers to characterize B cell populations with high specificity and sensitivity.

• B cell Depletion and Functional Studies: 1D3 has been used in vivo to deplete B cells for mechanistic and preclinical studies, including elucidating the role of B cells in immune response, autoimmunity, and cancer. Studies demonstrate effective depletion of B cells without targeting other lineages, allowing for clean experimental models for B cell function.

• Recombinant Expression and Engineering: Recent literature describes the successful de novo sequencing, synthesis, and recombinant expression of 1D3 heavy and light chain genes to generate a functionally equivalent recombinant antibody (R1D3). This enables more reproducible, scalable, and defined production compared to traditional hybridoma-derived antibody, and supports applications such as immunoprecipitation and protein interaction studies.

• Antigen Targeting and Therapy Development: The 1D3 clone, or affinity-matured derivatives, has been leveraged as a surrogate targeting domain in the development and preclinical testing of anti-CD19 therapies, such as bispecific antibodies and CAR T cells, by facilitating selective B cell targeting, depletion, or modulation.

• Tool for Investigating B cell Development and Disease: The widespread citation and use of 1D3 have contributed to advancing understanding of B cell biology, such as developmental stages, function in immune responses, and pathogenesis in diseases like lupus, lymphoma, and other immunopathologies.

• Specificity and Performance: 1D3 is reported to offer robust specificity and performance under diverse experimental conditions, but it is still recommended that each application be empirically validated (e.g., for different fixatives or conjugates).

In summary, the key scientific findings stemming from the use of clone 1D3 revolve around its reliability for mouse B cell detection, its validated role in B cell depletion studies, its utility in antibody engineering and recombinant production, and its critical enabling role in B cell–focused immunological research and therapeutic development.

Dosing regimens of clone 1D3 (anti-mouse CD19) vary substantially across mouse models, depending on experimental goals, mouse strain, and endpoints, with adjustments in dose, frequency, and duration to achieve efficient B cell depletion or as part of switch protocols.

Key points of variation and dosing details:

• Dose and Frequency: Widely cited protocols use single low doses for cell labeling and high repeated doses for robust B cell depletion or in switch regimens for iterative depletion. For depletion, typical published doses are around 300 µg per mouse, given in combination with anti-B220, or as monotherapy.
• Route: Intravenous (IV) or intraperitoneal (IP) injections are commonly used.

Strain/Model-Dependent Adjustments

• Syngeneic Tumor Models: Protocols in C3H mice, for instance, use 1 mg/kg administered intravenously every other day for eight doses—repeated in cycles with rest periods for iterative depletion and switch-control of B cell populations.
• Genetically Engineered Strains: Dosing may need adjustment for the mouse’s immunological profile to ensure efficient depletion because sensitivity to B cell depletion by 1D3 may differ across strains.
• A20 lymphoma model: Dosing schedules in the A20 model aimed at establishing minimal effective dose typically correlate with the tumor burden and engraftment schedule, and may be adapted to achieve specific depletion or therapeutic outcomes.

Combination Therapies

• For maximal B cell depletion, 1D3 is often used alongside anti-B220 (RA3.3A1/6.1) at matched doses (e.g., 300 µg each per mouse, IP) to target a broader range of B cells.
• In CAR-T cell protocols, 1D3 is administered in cycles, often after cyclophosphamide preconditioning, and may use iterative switch doses for population control.

Summary Table: Typical 1D3 Dosing Regimens (by application/model)

In summary: Clone 1D3 dosing regimens are flexibly adjusted with mouse strain, immunologic characteristics, and experimental needs, ranging from single labeling doses to prolonged, high-dose cycles for depletion or switch control, with combination therapies for maximal effect.

If you need a specific regimen for a particular mouse strain, disease model, or experimental readout, protocols are best confirmed in the literature or by consultation with the reagent supplier.