Anti-Human CD8a [Clone OKT-8] — Purified in vivo GOLD™ Functional Grade

Clone OKT-8 is most commonly used in vivo for the depletion of human CD8+ T cells in humanized mouse models—that is, mice engrafted with human immune systems or tissues expressing human CD8α. This application targets the human CD8α molecule, and OKT-8 does not react with mouse CD8+ T cells, making it unsuitable for classical murine models with only endogenous mouse cells.

Key details and applications include:

• Humanized Mouse Models: OKT-8 is used to specifically deplete human CD8+ T cells in mice reconstituted with human immune cells, allowing researchers to study the function of these cells in immune responses, infection, transplantation, autoimmunity, and especially tumor immunology or viral clearance.
• Functional Blocking/Neutralization: Besides depletion, OKT-8 may be used for functional blockade of human CD8+ T cell activity in vivo as well as ex vivo, to dissect the role of CD8+ T cells in immune function.
• Flow Cytometry and Phenotyping: Although not an in vivo application per se, OKT-8 is also widely used to identify and enumerate human CD8+ T cells in tissue and blood from humanized mice due to its high specificity.

Limitations and Alternatives:

• OKT-8 is not effective for the depletion of mouse CD8+ T cells; for that, clones such as 53-6.7 or 2.43 are commonly used.
• Crossreactivity with non-human primates is reported, but OKT-8 mainly targets human CD8α.

Summary Table: OKT-8 Clone in Mice

References indicate broad adoption of OKT-8 for in vivo CD8+ T cell depletion in humanized mice, as well as its use in functional studies of human T cell biology within these chimeric models.

Other commonly used antibodies or proteins in the literature with OKT-8 (which recognizes CD8α) include antibodies targeting different T-cell markers such as OKT3 (CD3) and OKT4 (CD4), as well as alternative anti-CD8 clones like SK1, MCD8, 32/M4, C8/144B, DK25, and 2ST8.5H7.

Key co-used antibodies and proteins:

• OKT3 (anti-CD3): Used to identify all T cells; often combined with OKT8 to distinguish cytotoxic/suppressor T cells from other subsets.
• OKT4 (anti-CD4): Marks helper/inducer T-cell subsets, allowing for discrimination between CD4+ and CD8+ T-cell populations when used with OKT8.
• Alternate anti-CD8 clones:
  • SK1, DK25, MCD8, 32/M4, C8/144B, 2ST8.5H7: These anti-CD8α or anti-CD8β antibodies are used with OKT8 for cross-validation or multiplex staining; some affect pMHCI tetramer binding differently than OKT8.
  • RPA-T8, HIT8a: Frequently used in flow cytometric analysis to identify CD8+ cells; do not block OKT8 binding, permitting simultaneous use in multi-color panels.
• Functional markers:
  • Co-staining with antibodies against activation markers (e.g., CD25, CD69), memory markers (e.g., CD45RO, CD62L), or NK cell markers (e.g., CD16, CD56) is common in immunophenotyping alongside OKT8, though not detailed in these results.

In summary, OKT8 is most frequently used in conjunction with OKT3 (CD3), OKT4 (CD4), and alternative CD8 antibody clones (such as SK1, DK25, RPA-T8, HIT8a), as well as other lineage or activation markers, to comprehensively profile T-cell subsets and function.

Key findings from scientific literature citing clone OKT-8 (anti-CD8 monoclonal antibody) highlight its specificity for human CD8^+^ T cells, its capacity to enhance functional assays, and its utility in flow cytometry and immunophenotyping.

• Specificity and Activation: OKT8 is highly specific for CD8^+^ T cells, and it can induce effector function in these cells. It stimulates the release of chemokines (MIP1α, MIP1β, RANTES) from CD8^+^ T-cell clones, an effect not seen with other anti-CD8 antibodies or CD4^+^ clones, indicating that its action is largely restricted to CD8^+^ T cells.

• Enhanced Detection: Preincubation with OKT8 enhances the staining intensity of CD8^+^ T cells when using peptide-MHC class I (pMHCI) tetramers, particularly for ligands with low affinity. This means OKT8 is valuable for identifying antigen-specific CD8^+^ T cells—especially those with weak TCR/pMHCI interactions found in some anti-cancer and autoimmune responses.

• Flow Cytometry Utility: OKT8 is widely used for flow cytometric analysis of human peripheral blood cells. It consistently and reliably stains CD8 on T cells, and its applications have been validated across multiple platforms and large cell count ranges.

• Genetic and Environmental Influences: Studies using OKT8 in immunophenotyping reveal periodic reductions in circulating OKT8^+^ cells associated with specific HLA types (notably HLA-DR2), suggesting genetic factors combine with environmental influences to determine CD8^+^ T cell phenotypes in contexts such as multiple sclerosis.

• Cell Type Cross-Reactivity: OKT8 has been reported to bind to some non-human cell types (e.g., sheep oligodendrocytes), but its use is primarily for human T-cell identification and functional profiling.

• Functional Subsets: Research employing OKT8 demonstrates that certain cytotoxic T lymphocyte subsets (OKT8^+^ cells) are distinct in their HLA antigen recognition and immune activity when compared to OKT4^+^ (CD4^+) subsets.

In summary, the clone OKT-8 antibody is a critical tool for immunological research, notably improving the detection and characterization of CD8^+^ T cells, enabling functional studies of T-cell responses, and aiding in the exploration of immunogenetic interactions in disease settings.

Dosing regimens for clone OKT-8 (OKT8) in mouse models primarily depend on whether the mice express human CD8, as OKT8 specifically targets human CD8α and not the native mouse CD8. OKT8 is most commonly used in humanized mouse models, where dosing varies according to the type of humanization, experimental goal, and administration route.

Key Points on Dosing Variability:

• Species/Model Specificity:

  • OKT8 targets human CD8α, and is functionally relevant only in mice that express human CD8, such as PBMC-humanized or HLA-transgenic mice.
  • In regular (non-humanized) mouse models, OKT8 is not effective for depleting CD8+ T cells, so other clones (like 2.43 or 53-6.7) are preferred.

• Reported Dosing Regimens:

  • While there is no universal standard for OKT8 dosing in mice, doses are generally adapted from cell-staining protocols (e.g., flow cytometry) and adjusted for in vivo use.
  • Dosing in humanized mouse studies is typically in the range of 100–250 μg per mouse, given intraperitoneally or intravenously—mirroring dosing used for other monoclonal antibodies in mice. However, precise regimens are often optimized per experimental need and publication, due to limited systematic data for OKT8 in vivo use in published guides.
  • Dosing frequency can vary. Commonly, antibodies for immune cell depletion or receptor engagement are administered every 3–7 days, but this is often empirically optimized depending on depletion kinetics, antibody pharmacokinetics, and duration of study.

• Example Application:

  • In humanized mouse models, studies may use OKT8 at 200 μg per mouse, intraperitoneally, every 3–4 days to achieve sustained depletion or modulation of the human CD8+ compartment. (This is inferred by analogy to other anti-CD8 protocols and supported by technical sheets and vendor recommendations.)
  • For in vitro or ex vivo cell marking (not depletion) in flow cytometry, much lower concentrations (sub-μg per test) are used.

Model/Strain Considerations:

Additional Context and Cautions:

• Depletion Efficiency: Degree of depletion may vary based on mouse humanization level, antibody dose, and duration of treatment. Residual human CD8+ T cells may persist at the tissue level even when peripheral blood shows depletion, necessitating tissue-specific analysis.
• Immune Response: Repeated dosing may induce anti-mouse antibody responses even in immunodeficient mice if they contain some residual B cells or after engraftment.
• Alternative Clones: For mouse CD8+ depletion, researchers generally use clones like 2.43 or 53-6.7. OKT8 is not suitable for wild-type or non-humanized mice.

Cited Evidence & Source Types

• Product datasheets and reviews consistently note OKT8 targets human CD8α and is used primarily in humanized mouse models.
• In vivo antibody dosing guides (not clone-specific, but broadly informative) recommend 100–250 μg per mouse as a starting point for monoclonal antibody interventions against lymphocyte antigens, with adjustment according to response.
• Peer-reviewed studies describing anti-CD8 depletion in PBMC-humanized mice or similar models often cite doses in this range but seldom provide standardized protocols; most optimization is empirical.

In summary, OKT8 dosing in mouse models is model-dependent: it is relevant only in mice expressing human CD8. Where applicable, typical regimens use 100–250 μg per mouse, given every 3–7 days intraperitoneally or intravenously, with details tailored to the experimental setup.