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

The clone 1D3 is a monoclonal antibody targeting mouse CD19 and is used in in vivo mouse studies primarily for B cell depletion and as the antigen-binding domain in the construction of murine anti-CD19 CAR-T cells.

• Direct use of 1D3 antibody for B cell depletion: The 1D3 monoclonal antibody has been shown to deplete B cells in vivo in mice, although its efficacy can depend on the disease model and sometimes requires combination with other antibodies for optimal depletion.
• As a CAR (Chimeric Antigen Receptor) component: The antigen binding domain (single-chain variable fragment, scFv) from 1D3 is frequently used to construct murine CARs targeting CD19. In these studies:
  • Mouse T cells are transduced with a CAR construct containing the 1D3-derived scFv.
  • These CAR-T cells are then adoptively transferred into recipient mice (often after irradiation and tumor cell challenge).
  • In vivo, these 1D3-based CAR-T cells lead to effective removal of B cells (normal and malignant), regression of lymphoma, and improve survival, as demonstrated in syngeneic mouse models of lymphoma.

Supporting details:

• The 1D3 mAb and CARs using the 1D3 scFv mediate B cell (CD19+) depletion, contributing to both therapeutic (anti-tumor, autoimmunity) and experimental purposes.
• In lymphoma models, 1D3-derived CAR-T cells eradicated both lymphoma and normal B cells and provided long-term protection from tumor re-challenge.
• The 1D3 scFv is one of the standard choices, along with FMC63, for targeting murine CD19 in mouse CAR-T and immunotherapy research.

Key applications in vivo:

• Depletion of B cells to model and investigate B cell–dependent diseases.
• Testing new CAR designs or gene editing approaches by assessing efficacy and toxicity of experimental anti-CD19 CAR-T cells.
• Comparing CAR-T efficacy to antibody therapy, as the 1D3 mAb alone is less effective than 1D3-based CAR-T cells for tumor eradication.

In summary, clone 1D3 is a cornerstone reagent in murine B cell and CAR-T cell research, used both as a depleting antibody and, more commonly, as the antigen-recognition element in anti-mouse CD19 CAR-T constructs for in vivo mouse studies.

The antibody 1D3, commonly used against mouse CD19 for B cell identification and depletion, is frequently paired with several other antibodies in immunological studies for broader characterization or more effective cell depletion. Key proteins and antibodies used alongside 1D3 include:

• Anti-mouse B220 (clone RA3.3A1/6.1): B220 (CD45R) is another widely used pan-B cell marker; combining anti-CD19 (1D3) and anti-B220 allows for more comprehensive identification or depletion of B cell populations.
• Anti-mouse CD22 (clone Cy34.1): CD22 is a B cell-restricted adhesion molecule, used in multi-parameter phenotyping with CD19 to distinguish B cell subpopulations or enhance depletion in combination therapies.
• Anti-rat ? light chain (clone MAR 18.5): When using rat IgG antibodies in vivo (such as 1D3, which is of rat origin), anti-rat ? light chain can help deplete rat antibody-tagged cells or verify depletion efficacy.

Studies also commonly assess these B cell populations in conjunction with CD21 and CD81, as these form part of the CD19 co-receptor complex; although direct antibodies to these proteins may be less frequently reported in the literature in combination protocols, their relevance in B cell signaling is widely acknowledged.

For cellular identification and depletion protocols, these antibodies are typically used together in flow cytometry or in vivo depletion strategies to achieve higher specificity or complete removal of B cell lineages.

In summary, the most common antibodies or proteins used with 1D3 are:

• B220 (pan-B cell marker)
• CD22
• CD21, CD81 (functionally/contextually relevant)
• Rat ? light chain (when working with rat-origin antibodies in a mouse model).

Their combined use enables more comprehensive analysis and effective experimental manipulation of B cell populations in mouse models.

Clone 1D3 is a monoclonal anti-mouse CD19 antibody widely cited in scientific literature, primarily as a key reagent for B cell detection, depletion, and as a targeting domain in mouse CAR T cell research. Key findings from studies citing clone 1D3 include:

• Isolation and Sequencing: The 1D3 clone's antibody sequences have been isolated from hybridoma cells, and its kinetic binding parameters to mouse CD19 have been characterized, demonstrating high specificity and utility for engineering purposes.

• Role in CAR T Cell Development: The single chain variable fragment (scFv) from the 1D3 antibody has been used as the targeting ligand in second-generation mouse CAR T cell constructs. These constructs enable specific recognition and depletion of murine CD19+ B cells, allowing preclinical in vitro and in vivo CAR T cell studies.

• Comparative Binding: Competition assays with other anti-mouse CD19 antibodies show that 1D3 binds to distinct, but sometimes overlapping, epitopes on the CD19 antigen.

• Functional Efficacy: In engineered mouse T cells, 1D3-based CARs enable effective recognition and killing of CD19-expressing mouse B cell tumor lines, similar to how human CAR T cells using FMC63 scFv target human CD19.

• Screening and Quantification Tool: The 1D3 antibody is commonly employed in flow cytometry panels for accurately identifying and quantifying mouse B cells in various tissues due to its strong and specific binding properties.

• Genetic Fidelity and Quality Control: Literature on clone quality highlights the necessity for sequence verification due to clone contamination or sequence ambiguity risks. This ensures the authenticity and reproducibility of reagents like 1D3 used in research.

The 1D3 clone is considered a reference standard in mouse CD19 research, providing both a reliable detection antibody and a validated targeting module for experimental immunotherapy platforms. Its widespread adoption underscores its specificity, reproducibility, and cross-comparability with human CD19 reagents.

Dosing regimens for clone 1D3 (anti-mouse CD19 monoclonal antibody) can vary significantly depending on the specific mouse model and experimental context, particularly whether the intent is for B cell depletion, immunophenotyping, or use as a switch for CAR-T or other engineered cell therapies.

Key variations in dosing regimens across mouse models:

• In studies utilizing B cell depletion or functional blockade, 1D3 is typically administered at doses ranging from 100 µg to 250 µg per mouse, usually by intraperitoneal (i.p.) injection. The injection frequency can vary from a single dose up to every 3–4 days for several weeks, depending on the duration and intensity of depletion desired. The mouse strain (e.g., C57BL/6, Balb/c) does not usually alter the basic dosing pattern, but the response may differ because of background genetic factors.

• In switchable CAR-T cell therapy models, for example, one study used a 1 mg/kg intravenous (i.v.) dose of anti-mouse CD19 switch (analogous to 1D3) every other day for eight doses, followed by a 2-week resting period, for a total of three cycles. This regimented, cyclic dosing allows for precise modulation of B cell populations and CAR-T cell activity. The referenced study used this regimen in C3H mice bearing syngeneic tumors, reflecting the need for repeated and controlled B cell depletion in an immunotherapy setting.

• For immunophenotyping (e.g., flow cytometry), significantly lower doses of 1D3 (typically 0.1–2 µg per mouse, administered intravenously) are employed to label B cells for short-term in vivo detection. These amounts do not cause depletion and are not used repetitively.

Summary Table: 1D3 Dosing Regimens in Various Contexts

Important supporting details:

• The effect of 1D3 dosing can differ between mouse strains due to differences in their immune systems, notably in syngeneic tumor models versus genetically engineered strains.
• For B cell depletion, both the dose and frequency must be adjusted for the duration of depletion required and for experimental endpoints.
• While often used i.p., some protocols favor i.v. delivery, particularly for uniform systemic exposure or when combined with cell therapy platforms.

In summary: Dosing regimens for clone 1D3 in mouse studies range from low, single doses for labeling, to high, repeated doses for depletion or as switch doses in CAR-T therapy. Frequency and route (i.v. vs. i.p.) are tailored to the experimental goal and may differ with mouse strain and disease model.