Anti-Human CD3 [Clone UCHT-1] — Purified in vivo PLATINUM™ Functional Grade

Clone UCHT-1, an anti-human CD3 monoclonal antibody, is commonly used in in vivo mouse studies, but its applications are specific to models incorporating human immune cells or humanized CD3 due to its strict reactivity for human (not mouse) CD3.

Key in vivo applications in mice include:

• Humanized or Xenograft Models: UCHT-1 is employed in mice engrafted with human immune cells or expressing human CD3, often to activate, track, or therapeutically manipulate human T cells within a murine host. This is especially common in humanized mouse models (e.g., CD3E humanized mice) where the mouse Cd3e gene is replaced with its human counterpart, allowing functional interaction with UCHT-1.

• Evaluation of Bispecific Antibodies and Immunotherapies: In vivo studies use UCHT-1 (or related anti-human CD3 antibodies) to test the efficacy of bispecific antibodies—such as those recruiting human T cells to attack tumors—or other immunomodulatory agents. For example, anti-CD3 bispecifics like blinatumomab have been evaluated for their ability to facilitate T cell-mediated tumor regression in mice with human immune components.

• Activation and Depletion of Human T Cells: UCHT-1 can be used to experimentally activate human T cells for studies of T cell signaling, immune responses, or to induce T cell depletion in vivo, helping model mechanisms relevant to therapies or immune diseases.

• Targeted Delivery and Control Mechanisms: Modified UCHT-1 antibodies (e.g., conjugated with folate and photosensitizers) have been utilized for light-activated, spatially controlled targeting of human T cells in tumor models, demonstrating utility in precise immunological manipulation and tumor immunotherapy research.

Crucial limitations:
UCHT-1 does not react with native mouse CD3—its in vivo use is limited to mice harboring human CD3, human T cells, or genetically humanized mouse models. In conventional (non-humanized) mice, UCHT-1 has no functional target.

Summary Table: Common in vivo applications of Clone UCHT-1 in Mice

In summary, UCHT-1 is a tool for mechanistic and therapeutic studies involving human T cells in mice, especially in translational research on cancer, immunotherapy, and immune regulation, but only when human CD3 is present in the model.

UCHT1 is commonly used alongside several other antibodies and proteins in immunological research, particularly for T cell studies and flow cytometry applications.

Commonly Combined Antibodies

CD19 antibodies are frequently paired with UCHT1 to distinguish between different lymphocyte populations. This combination allows researchers to differentiate T cells (CD3+) from B cells (CD19+) in mixed lymphocyte populations. In flow cytometry protocols, UCHT1 conjugated to FITC is often used together with APC-conjugated anti-CD19 antibodies for multi-color phenotyping of human whole blood cells.

OKT3 represents another important anti-CD3ε monoclonal antibody that is often compared or used alongside UCHT1 in functional and binding studies of the T cell receptor complex. Structural analyses have revealed that while both antibodies target CD3ε, they have overlapping but distinct binding sites. OKT3 buries 1,220 Ų of surface area and contacts residues ε35, ε47, ε49, and ε80-86, whereas UCHT1 contacts all of these residues plus additional ones including ε44, ε45, ε48, ε56, and ε78, burying a larger surface area of 1,789 Ų. The UCHT1 binding site extends more deeply into the groove between the F-G loop and C′ strand of CD3ε compared to OKT3.

Functional Applications

In tumor immunology studies, UCHT1 has been used to enhance the cytotoxic activity of γδ T cells against various cancer cell lines. Researchers have demonstrated that UCHT1 antibodies and their Fab fragments can significantly increase tumor killing by zoledronate-expanded human Vγ9Vδ2 γδ T cells against B cell lymphoma lines like Daudi and Raji, as well as pancreatic ductal adenocarcinoma cells.

Key findings from scientific literature on clone UCHT-1 focus on its unique ability to bind and stabilize the CD3ε subunit of the human T cell receptor (TCR) complex, impacting T cell activation, signaling, and functional outcomes.

• Structural binding: UCHT-1 binds to a large, nonlinear surface epitope on the acidic region of CD3ε, opposite the heterodimer interface, occluding this region from direct interaction with the TCR and forming stable complexes with CD3ε/δ or CD3ε/γ heterodimers. Its binding involves extensive interactions: salt bridges, hydrogen bonds, and van der Waals contacts, particularly with a groove created by the F-G loop and C′ strand of CD3ε.

• Functional effects on T cell activation: Unlike other anti-CD3 clones (e.g., OKT3), UCHT-1 can induce T cell proliferation independently of interleukin-2 (IL-2) and in some contexts, without requirement for secondary costimulatory signals. This has been observed both in basic studies and in engineered T cell receptor formats, where UCHT-1 enabled more robust activation than other clones.

• Tumor immunology: UCHT-1 Fab fragments enhance tumor cell killing by human γδ T cells, correlated with increased activation markers (such as CD69, CD25) and cytokine production (IFNγ, TNFα). This effect appears linked to UCHT-1’s ability to stabilize the γδ TCR in its active CD3 conformation in the presence of natural ligand, generating qualitatively distinct activation signals.

• Pan-T cell marker: UCHT-1 is a pan-T cell marker, reacting with the CD3ε subunit expressed on approximately 95% of mature T cells, making it widely used for T cell identification, isolation, and functional assays.

• Epitope specificity and signal strength: Differences in epitope recognition and downstream signaling compared to other anti-CD3 clones (such as OKT3) explain variations in biological responses, such as proliferation, activation, and cytokine production.

• Biotechnological applications: UCHT-1 has been used in formats such as bispecific antibodies, antibody-drug conjugates, and chimeric antigen receptor designs to leverage its robust T cell activation for therapeutic purposes.

In summary, UCHT-1 citations are notable for revealing a unique binding pattern to CD3ε, strong activation potential without requiring classic costimulatory signals, and utility in both research and clinical immunology.

Dosing regimens for the UCHT-1 clone, which is an anti-human CD3 antibody, can vary significantly across different mouse models. These variations are primarily dependent on several factors, including:

1. Study Design: The purpose of the study influences the dosing regimen, whether it's for T-cell activation, depletion, or therapeutic interventions.

2. Mouse Strain: Different strains of mice may have varying levels of immune response and tolerance to the antibody, which affects dosing.

3. Tumor Type: The presence and type of human tumor xenografts can influence the required dose due to differences in tumor burden and growth rates.

4. Mechanistic Goals: Whether the goal is to enhance T-cell function, monitor T-cell populations, or induce specific effects on T-cell populations can dictate the dosing strategy.

For specific dosing amounts, intervals, and routes, it often requires context-specific information tailored to the particular study or experiment. For instance, in models involving human tumor xenografts or humanized mice, the dosing may be adjusted to ensure optimal targeting of human T cells while minimizing potential toxicity or adverse reactions in the murine host.

In general, dosing regimens for UCHT-1 in mouse models are context-dependent and require careful consideration of these factors to achieve desired outcomes.