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

Clone UCHT-1 is a monoclonal antibody specific for human CD3?, frequently used in in vivo mouse studies involving human immune cells engrafted into mice (i.e., humanized mouse models).

• UCHT-1 does not recognize mouse CD3; its use is generally restricted to models where human CD3-positive cells are present (such as immunodeficient mice reconstituted with human PBMCs, hematopoietic stem cells, or tumors expressing human CD3).

• Mechanisms of use in mouse studies:

  • Activation or depletion of human T cells: UCHT-1 binding/crosslinking leads to activation and/or depletion of human T cells via the CD3/TCR complex.
  • Targeted delivery or functional assays: UCHT-1 has been conjugated to molecules (e.g., folate, drugs, photosensitive groups) to locally modulate human T cells within the mouse, such as photolysis-driven tumor targeting.
  • Immunophenotyping: UCHT-1 is used to identify, isolate, or quantify human T cells in mouse tissues via flow cytometry or immunohistochemistry.

Example (from the literature):

• A published study administered UCHT-1–folate conjugates into mice bearing tumors composed of human cells, then used local UV irradiation to activate the antibody conjugate in situ, thus targeting human T cells in a spatially controlled manner.

Key points for in vivo use:

• Application is restricted to humanized or xenograft models with human T cells.
• Formats exist that are pre-validated for in vivo mouse injection (low endotoxin, bulk purified).
• Common endpoints include measurement of human T cell activation, depletion, or anti-tumor immune effects—always specific to human (not endogenous mouse) CD3.

Summary Table: UCHT-1 Use in Mouse Studies

Note: Since UCHT-1 is mouse IgG1 and does not cross-react with mouse CD3, it is not used for immunomodulation in normal, non-humanized mice.

UCHT-1 is commonly used in conjunction with other antibodies or proteins targeting distinct immune cell markers to identify or characterize cell populations in immunological studies, especially by flow cytometry and immunohistochemistry.

Typical antibodies and proteins used alongside UCHT-1 include:

• CD19: An antibody frequently combined with UCHT-1 to distinguish T cells (CD3+) from B cells (CD19+) in mixed lymphocyte populations.
• OKT3: Another monoclonal antibody directed against CD3?, often compared or used with UCHT-1 in functional or binding studies of the T cell receptor complex.
• Secondary reagents: Such as APC-labeled anti-mouse IgG antibodies, commonly employed for detection when UCHT-1 is used as an unconjugated primary antibody.
• Other T or B cell markers: In multi-color panels, antibodies against markers like CD4, CD8 (T cell subsets), CD45, or CD20 (other B cell markers) are typically included alongside UCHT-1 to further delineate or characterize lymphocyte subsets.

In experimental protocols, UCHT-1 has also been referenced in combination with:

• Fab fragments (produced from UCHT-1 itself), especially in studies aiming to distinguish activating versus non-activating effects on T cells.
• Chemical agents or activating proteins: Such as concanavalin A for cell stimulation or zoledronate for ?? T cell expansion in cytotoxicity assays.

These combinations allow for precise immunophenotyping and functional interrogation of immune cells in both basic and translational research contexts.

Key findings from clone UCHT-1 citations center on its ability to bind and stabilize the CD3? subunit of the T cell receptor (TCR) complex, enhancing T cell activation and cytotoxicity, particularly in human ?? T cells.

• UCHT-1 binding stabilizes the active conformation of CD3: UCHT-1 binds the CD3? subunit at a region opposite the interface with CD3?, occluding this region from direct TCR interaction and stabilizing the CD3?/? heterodimer. Structural studies revealed high-affinity interactions involving multiple hydrogen bonds and salt bridges between UCHT-1 and CD3?.
• Enhancement of ?? T cell activation and tumor killing: Both full UCHT-1 antibody and its monovalent Fab fragments are shown to enhance tumor cell killing by human V?9V?2 ?? T cells. Notably, this enhancement occurs without requiring TCR cross-linking, implicating stabilization of the CD3 active conformation as the key mechanistic event.
• Mechanistic insight—Nck recruitment: UCHT-1-induced stabilization of the active CD3 conformation promotes recruitment of the signaling adaptor Nck to the proline-rich sequence (PRS) of CD3?, a mechanism previously established for ?? TCRs and now shown for ?? TCRs as well. This recruitment can be blocked by specific inhibitors, indicating pathway specificity.
• Functional outcomes of UCHT-1 treatment: The presence of UCHT-1 Fab fragments boosts ?? T cell activation markers (CD69, CD25) and proinflammatory cytokine expression (IFN?, TNF?). These effects are above and beyond those achieved by stimulation with natural phosphoantigen ligands alone.
• Structural biology applications: UCHT-1’s strong affinity for CD3 has enabled the successful crystallization of CD3?/? heterodimers for structural analysis, facilitating fundamental understanding of TCR architecture.

In summary, UCHT-1 serves as a powerful tool for both structural and functional interrogation of T cell activation via CD3?, with direct translational implications for modulation of immune responses and tumor cell killing by ?? T cells.

Dosing regimens for clone UCHT-1 (anti-human CD3 monoclonal antibody) vary across mouse models depending on factors such as antibody conjugation, tumor type, and experimental design. Published studies primarily report UCHT-1 use in xenograft models where human CD3-expressing cells are present, as standard immunocompetent mice do not express human CD3 and thus do not respond to UCHT-1.

In several xenograft models, UCHT-1 conjugated to folate (UCHT1-Fol-NPE) was administered to mice at varied doses and schedules, typically after tumor initiation:

• Female mice (batch c): Received UCHT1-Fol-NPE four days post-tumor initiation. Tumor weights varied, with averages notably lower in treated groups than controls; however, the precise dosing per mouse was not explicitly specified in the table.
• Female mice (batch d): Also dosed four days after tumor initiation, showing lower mean tumor weights in treated groups. Dosing schedule and amount were not detailed in the search result.
• Male mice (batch d): Similar protocol with reductions in tumor size in the treated groups, but again, dosing amount and schedule details were not specified, suggesting that regimen may be tailored for tumor model, sex, and batch.

Because UCHT-1 does not recognize murine CD3, its use in standard syngeneic mouse models is limited; it is predominantly utilized in humanized, xenograft, or transgenic mouse models engineered to express human CD3. In these settings, dosing parameters (amount per mouse, route, frequency) are determined by the experiment’s objectives (e.g., tumor targeting, immune activation) and conjugation strategy (e.g., folate attachment for tumor targeting).

In contrast, for commonly used antibodies targeting mouse immune checkpoints and cell surface markers, typical doses are 100–500??g per mouse, administered every 3–4 days via intraperitoneal injection, as summarized for clones like OKT3 or checkpoint inhibitors in cancer immunotherapy models. However, these do not directly apply to UCHT-1 unless specifically humanized mice are used.

In summary:

• UCHT-1 dosing in mouse models is context-dependent—requiring human CD3 expression or tumor xenografts.
• Specific dosing information (amount, interval, route) for UCHT-1 in published mouse models is often not detailed in summary tables but is typically tailored to experimental design.
• Direct comparison with other antibody clones targeting murine epitopes (e.g., anti-CD4, anti-CD8, anti-checkpoint antibodies) indicates dosing commonly in the range of 100–500??g per mouse, every 3–4 days, but UCHT-1 regimens may diverge based on target specificity and conjugation.

If further specificity (e.g., exact ?g/mouse or schedule for UCHT-1 in a named mouse model) is needed, consultation of full-text primary research articles is recommended, as regimens may be highly variable depending on the mouse strain, antibody formulation, and experimental goals.