Anti-Human CD38 (Clone OKT10) – Purified in vivo PLATINUM™ Functional Grade

OKT10 clone is utilized in in vivo mouse studies primarily as a targeting vehicle for radioimmunotherapy in cancer treatment research, particularly for multiple myeloma and other B cell malignancies.

Pretargeted Radioimmunotherapy Applications

The most prominent use of OKT10 in mouse studies involves a sophisticated pretargeted radioimmunotherapy approach. In this method, OKT10 is conjugated with DOTA (a chelating agent) and administered to tumor-bearing mice first, allowing it to bind to CD38-expressing cancer cells. After a predetermined interval (typically 24 hours), mice receive a clearing agent followed by radioactive yttrium-90 (^90^Y) labeled biotin, which then binds to the previously administered OKT10 construct.

Treatment Efficacy in Multiple Myeloma Models

Studies using L363 multiple myeloma xenograft models demonstrate remarkable therapeutic outcomes with OKT10-based treatment. Mice treated with OKT10-DOTA followed by ^90^Y-DOTA-biotin showed complete tumor regression within 6 days at higher dose levels (1200µCi), with 100% complete remissions observed by day 17. In contrast, untreated control animals required euthanasia within 17 days due to progressive tumor growth, with 78% requiring euthanasia within this timeframe.

The therapeutic effect is strictly dependent on the radioactive component - mice treated with OKT10 alone (without subsequent radioactive treatment) showed no tumor response and required euthanization by day 17, with tumors reaching 7837±3492% of their initial volume. However, mice receiving the complete pretargeted treatment protocol achieved 100% complete remissions by day 17, with 70% remaining alive and tumor-free at day 80.

Manufacturing Requirements for In Vivo Use

For in vivo applications, OKT10 antibodies are manufactured to cGMP standards with stringent endotoxin requirements. Quality antibodies for mouse studies contain less than 1.0 EU/mg endotoxin, with ultra-low endotoxin formulations available at less than 0.5 EU/mg for sensitive in vivo applications. The antibodies undergo multi-step affinity chromatography purification methods to achieve the high purity levels necessary for animal studies.

This approach represents a promising targeted cancer therapy strategy that leverages CD38 expression on malignant B cells to deliver cytotoxic radiation specifically to tumor sites while minimizing systemic toxicity.

Based on the information available for clone OKT10 antibodies, the correct storage temperature is 2-8°C (refrigerated conditions). This temperature range should be maintained while protecting the antibody from prolonged exposure to light.

Storage Duration Guidelines

For short-term storage, the antibody can be kept at 4°C for up to 3 months. However, for longer-term storage, it should be aliquoted and stored at -20°C or even at ?-70°C for extended preservation.

Important Storage Considerations

Aliquoting is crucial to avoid repeated freeze-thaw cycles, which can damage the antibody's functionality. The sterile packaged format allows for storage as received at 2-8°C for up to one month, but for longer storage periods, aseptic aliquoting into working volumes without dilution is recommended before freezing.

The consistent recommendation across multiple sources is that clone OKT10 should be stored at 2-8°C as the primary storage condition, with freezing options available for extended storage needs when properly aliquoted to prevent degradation from freeze-thaw cycles.

HB2 (anti-CD7) is one of the most commonly used antibodies in the literature alongside OKT10 (anti-CD38), particularly in studies involving immunotoxin-based therapies targeting leukemia cells.

In research on human T-cell acute lymphoblastic leukemia (T-ALL), both OKT10 and HB2 (targeting distinct antigens: CD38 and CD7, respectively) are frequently employed together. Combining OKT10-Saporin and HB2-Saporin immunotoxins has demonstrated increased cytotoxic efficacy both in vitro and in vivo compared to their use individually. The rationale is that targeting two antigens can overcome the heterogeneity of antigen expression in tumor cell populations and enhance toxin delivery. Sometimes, native OKT10 and HB2 antibodies (without toxin conjugation) are also used together as controls due to their ADCC (antibody-dependent cellular cytotoxicity) effect.

Other commonly studied reagents/proteins in conjunction with OKT10 (CD38) antibodies include:

• CD19 and CD20 antibodies, when the goal is to simultaneously characterize B cell maturation and activation states, since CD38 is prominently expressed during these stages.
• Saporin (a ribosome-inactivating protein) is used to construct immunotoxins for both OKT10 and HB2, studied both separately and in combination for enhanced therapeutic effect.
• Flow cytometry panels with OKT10 often include established cell surface markers such as CD19, CD45, and CD3 to provide comprehensive immunophenotyping, especially for hematopoietic and lymphoid cell analyses.

In summary, HB2 (anti-CD7) is the most consistently cited antibody used in tandem with OKT10 in functional experiments, especially in the immunotoxin and leukemia research context. Additional markers (e.g., CD19, CD20, CD45) are common in phenotyping settings for broader immune cell characterization.

Key findings from scientific literature on clone OKT10 center on its function as a monoclonal antibody specific for the cell surface antigen CD38, with extensive usage in immunology, hematology, and therapeutic research.

• Antigen Recognition and Cell Expression Patterns:

  • OKT10 selectively recognizes CD38, an antigen expressed broadly on pre-B lymphocytes, plasma cells, thymocytes, monocytes, as well as in malignancies such as acute lymphoblastic leukemia (ALL), Burkitt's lymphoma, multiple myeloma, acute myeloid leukemia (AML), and chronic lymphocytic leukemia (CLL).
  • The antigen is strongly expressed on activated T cells (in vitro or in vivo) but poorly on resting peripheral T cells. Double-staining experiments showed paradoxical results: sequential antibody treatment can induce visible expression of normally cryptic antigens in the cell membrane, suggesting that resting T cells possess unexpressed CD38 that can be revealed by antibody-induced membrane perturbation.

• Research and Diagnostic Applications:

  • OKT10 has been extensively cited (over 2,000 articles in recent years) for:
    • Fractionation of CD38+ and CD38? cell populations using magnetic cell sorting (MACS).
    • Flow cytometry for characterizing lymphocyte populations including analyses in non-human primates (e.g., Cynomolgus, Baboon, Rhesus monkeys).
    • Mapping and detecting CD38 expression in various hematopoietic and immune cell subtypes.

• Therapeutic Utilities:

  • Conjugation of OKT10 to therapeutic agents (such as the ?-emitter Astatine-211 (^211At)) enables targeted eradication of CD38+ multiple myeloma cells in preclinical disease models:
    • OKT10-conjugated ^211At selectively binds and kills CD38+ myeloma cells both in vitro and in murine xenograft models.
    • Radiolabeled OKT10 demonstrates highly specific binding to CD38+ cells and induces cytotoxicity, while CD38? cells are not affected, confirming antigen-specific activity.

• Cross-Species Reactivity and Epitope Mapping:

  • The anti-human CD38 reactivity of OKT10 has enabled its application for detecting CD38 in rhesus macaque hematopoietic cells, facilitating translational animal studies and comparative immunology.

Summary Table: Core Findings Associated with OKT10

These findings demonstrate the broad utility of OKT10 as a research and therapeutic tool, particularly through its targeting of CD38 and its versatility in diagnostics and preclinical studies.