Anti-Human CD2 [Clone LO-CD2a] — Purified in vivo GOLD™ Functional Grade

The clone LO-CD2a is commonly used in vivo in mice—specifically in humanized mouse models—to deplete human CD2+ T cells, induce immunosuppression, and prevent graft rejection after transplantation. Its applications utilize its specificity for human CD2, which is expressed primarily on human T cells, most thymocytes, and NK cells.

Key in vivo applications of LO-CD2a in mice include:

• T Cell Depletion: LO-CD2a depletes human CD2+ T cells via antibody-dependent cell-mediated cytotoxicity (ADCC) mechanisms, primarily using NK cells and activated monocytes.
• Immunosuppression: It inhibits immune responses by down-modulating CD2 on human cells, leading to decreased activation, proliferation, and cytokine production, and induces T cell apoptosis.
• Prevention of Graft Rejection/Organ Transplant Studies: It is widely employed in studies aimed at delaying or preventing acute or chronic rejection of transplanted organs in humanized mice, mimicking clinical scenarios.
• Induction of T Cell Hyporesponsiveness: LO-CD2a induces functional hyporesponsiveness in human T cells upon antigen restimulation, distinguishing it from other anti-CD2 antibodies.
• Models of Allotransplantation: Used in experiments involving organ and tissue transplantation between humans and mice to study immunoregulatory mechanisms and potential therapies.

LO-CD2a does not interact with mouse CD2, so its utility is confined to models where human CD2+ cells are present (e.g., human PBMC-engrafted or humanized mice).

Other notable characteristics:

• Induces minimal cytokine release and generally avoids severe side effects in vivo.
• Frequently utilized as a functional grade antibody with very low endotoxin levels, appropriate for preclinical immunological experiments and transplantation models.

In summary, LO-CD2a is principally applied in vivo to manipulate human immune cell populations in humanized mouse models, with a primary focus on transplantation, immunosuppression, and T cell depletion research.

LO-CD2a is frequently used in immunology research in combination with other antibodies or proteins, depending on the experimental context. The following are some of the most commonly used markers and proteins reported in the literature for co-use with LO-CD2a:

• CD3: Antibodies against CD3 are widely used with LO-CD2a, especially in studies of T cell function, activation, and depletion. CD3 is a core T cell receptor complex component and is a common marker for pan-T cell identification and stimulation.
• TCR Vβ family-specific antibodies: These are utilized to characterize and stimulate specific T cell receptor subpopulations and to examine T cell responses in more detail when used alongside LO-CD2a.
• Monocyte markers and other immune cell surface proteins: Markers that identify monocytes and other interacting immune cells (such as NK cells and thymocytes) are commonly used, given the role of these cells in LO-CD2a-mediated immune modulation.
• Other anti-CD2 antibodies: Such as Leu-5b, OKT11, and MT910, which recognize different epitopes or are used as controls in experiments testing CD2-mediated effects.
• CD58 (LFA-3): While not an antibody, this is a ligand of CD2 and is frequently considered in functional studies involving LO-CD2a to understand the CD2-CD58 interaction.
• Anti-CD48, CD59, and CD15: These proteins are related to or interact with CD2 and have been mentioned in the context of mapping CD2 biology and performing multi-marker immune phenotyping.
• Isotype controls and secondary antibodies: Used as standard controls in any immunological experiment to verify specificity.

In summary:
The most common protein and antibody partners co-used with LO-CD2a in the literature are CD3, various TCR Vβ family antibodies, monocyte and immune subset markers, and in some studies, other anti-CD2 antibodies as comparators or controls. Functional ligands like CD58 (LFA-3) are also central to mechanistic explorations.

Key findings from scientific literature on clone LO-CD2a (also known as BTI-322 or MEDI-507) emphasize its potent immunosuppressive properties, its mechanism of action in T-cell depletion and tolerance induction, and its applications in both experimental models and therapeutic contexts.

1. Potent Immunosuppressive and T Cell Depleting Agent

• LO-CD2a depletes CD2+ T cells in vivo, primarily via NK cell-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) and possibly monocyte involvement.
• Immunosuppression: It powerfully inhibits proliferation of human peripheral blood mononuclear cells (PBMCs) stimulated by mitogens, such as OKT3, and strongly suppresses mixed lymphocyte culture (MLC) responses in vitro.
• Low cytokine release: Unlike some other anti-CD2 antibodies, LO-CD2a induces very low cytokine release during T cell inhibition, reducing the risk of cytokine storm syndromes.

2. Mechanism and Unique Functional Characteristics

• Activation-Associated Depletion and Tolerance Induction: LO-CD2a uniquely induces unresponsiveness (“anergy”) upon restimulation with the same antigen—a property not seen with all anti-CD2 antibodies. This suggests not only depletion of reactive T cells, but also a shift in immune responsiveness.
• The Fc region of the antibody is necessary for this function; F(ab')₂ fragments do not reproduce the effect, indicating involvement of Fc receptor-expressing accessory cells (including monocytes).
• CD2 conformation changes and down-modulation play a role in the prolonged suppression and depletion.

3. Clinical and Experimental Relevance

• Allotransplantation: Originally and most extensively studied for its use as an immunosuppressive agent in organ allotransplantation, LO-CD2a can prevent and treat allograft rejection in preclinical models.
• Selective depletion: Siplizumab, the humanized version of LO-CD2a, similarly depletes memory and effector T-cell subsets, leaving regulatory subsets relatively preserved.

4. Specificity and Cell Targets

• CD2 is expressed on most mature human T cells, thymocytes, NK cells, and a subset of bone marrow cells.
• LO-CD2a does not induce proliferation of resting T cells and is selective for activated and proliferating subsets during immune responses.

5. Supporting and Seminal References in the Field

• LO-CD2a’s action, including primary citations, has been reported in respected journals and patents, such as:
  • Bierer BE, et al., Annu Rev Immunol. 7:579–599 (1989)
  • Latinne D, et al., Int Immunol. 8(7):1113-1119 (1996)
  • Dumont C, et al., J Immunol. 160(8):3797-3804 (1998)
  • Nizet Y, et al., Transplantation. 69(7):1420-1428 (2000)
  • Xu Y, et al., Clin Exp Immunol. 138(3):476-483 (2004)

Summary Table: LO-CD2a Key Features

These findings underpin the scientific and clinical interest in LO-CD2a for targeted immunosuppression, especially where selective T cell inhibition and tolerance are advantageous.

Dosing regimens of clone LO-CD2a (anti-human CD2 antibody) vary widely across different mouse models and are not standardized; they are primarily determined by the experimental design, such as the type of humanized or chimeric mouse model used, the immune cells present, and the intended immunosuppressive or T-cell depleting effect.

Key context and supporting details:

• LO-CD2a targets human CD2 and does not react with mouse CD2, so it is used almost exclusively in mice engrafted with human immune cells (e.g., hu-SCID, NSG with human PBMCs), in studies of human T cell depletion, graft rejection, or immunosuppression.
• Dose selection is empirical. There is no universal dosing regimen; researchers establish doses based on the model's specifics, desired immunological effect (e.g., level of T cell depletion, graft protection), and safety for the mice. Doses are most often adapted from in vitro functional assays, human clinical experience, and limited published allotransplantation/xenotransplantation studies.

Typical examples, supported by references:

• In vitro experiments: LO-CD2a (also called BTI-322) is commonly used at concentrations such as 100–200 ng/ml in mixed lymphocyte reactions or cell cultures to assess T cell function inhibition.
• In vivo experiments:
  • Most available literature references use doses ranging from low microgram to milligram quantities per mouse (e.g., 10–30 μg per injection for T cell depletion, or higher doses for graft rejection prevention), usually administered intraperitoneally (IP) or intravenously (IV).
  • Dosing frequency (single versus multiple dosing) and interval are highly variable and depend on the duration of the study and the persistence of human T cells: some protocols, for example, might use daily dosing for several days, or intermittent dosing spaced by several weeks.
• Regimen adjustments: Researchers may adjust the regimen for chimeric mice with different levels of human T cell engraftment, or in response to observed toxicity, clinical signs, or incomplete T cell depletion.

Summary table:

• There is no one-size-fits-all regimen, and dosing should be tailored to the experimental context, desired immunomodulatory effect, and human cell engraftment status in the mouse.
• When adapting human doses for mice, calculations are usually based on mouse weight (e.g., 0.5–1 mg/kg) or by targeting a specific T-cell depletion threshold.

If you need guidance for a specific mouse model or immunosuppressive endpoint, protocol parameters from similar published experiments should be consulted for starting doses, with titration or adjustment as required for safety and efficacy.