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

Use of Clone OKT10 in In Vivo Mouse Studies

Clone OKT10 is a monoclonal antibody that specifically recognizes human CD38, a cell surface glycoprotein highly expressed on plasma cells and certain B cell malignancies. While OKT10 is primarily used in vitro for research and diagnostics, there are specific in vivo applications, particularly in preclinical models of human cancer.

Key Applications in Mouse Models

Preclinical Radioimmunotherapy for Multiple Myeloma

• OKT10 has been used in the development of pretargeted radioimmunotherapy for multiple myeloma (MM). In these studies, a modified form of OKT10 (OKT10-CC) is administered to mice bearing human MM xenografts, followed by a radiolabeled agent (??Y-DOTA-biotin).
• The antibody serves as a targeting vehicle, binding to CD38 on tumor cells and allowing subsequent delivery of a cytotoxic radionuclide. This two-step approach minimizes nonspecific radiation exposure and enhances tumor targeting.
• Mice treated with OKT10-CC alone (without radiation) showed no tumor response, confirming that the therapeutic effect relies on the subsequent delivery of the radionuclide, not on the antibody alone.
• Animals receiving the full regimen (OKT10-CC followed by ??Y-DOTA-biotin) demonstrated rapid and complete tumor regression, with 100% complete remissions observed at higher doses, and prolonged survival compared to controls.

Experimental Protocol

• Antibody Administration: Mice are injected with 1.4 nmol (300 µg) of OKT10-CC, which localizes to CD38-positive tumor xenografts.
• Radiolabel Delivery: After allowing time for antibody localization, a clearing agent and then ??Y-DOTA-biotin are administered. The radiolabel binds to the antibody-tumor complex, delivering a targeted cytotoxic dose to the tumor.
• Monitoring: Tumor growth and animal survival are closely monitored. Mice are euthanized if tumors reach 10% of body weight or show ulceration, per institutional guidelines.
• Outcome: This regimen leads to dramatic tumor shrinkage and improved survival, especially when a sufficient radionuclide dose is delivered.

Limitations and Specificity

• No Standalone Effect: OKT10 alone does not exhibit significant anti-tumor activity in these models; its value is as a targeting agent for radionuclide delivery.
• Human CD38 Specificity: Since OKT10 recognizes human CD38, these studies require immunodeficient mice engrafted with human tumor cells (xenografts), not wild-type mice.
• Not for Immunomodulation: Unlike some antibodies (e.g., OKT3), OKT10 is not used in these studies to modulate the immune system or induce cytokine release.

Summary Table

Conclusion

In vivo, the OKT10 clone is primarily used as a targeting agent in pretargeted radioimmunotherapy studies for human multiple myeloma xenografts in immunodeficient mice, enabling precise delivery of radionuclides to CD38-expressing tumors and resulting in potent anti-tumor effects. It is not effective as a standalone therapy in these models and does not induce significant immune modulation.

Based on the information available, the clone OKT10 is a mouse monoclonal antibody that recognizes the CD38 antigen, and it should be stored at 2-8°C (36-46°F).

Storage Requirements

Multiple sources consistently indicate that OKT10 antibodies require refrigerated storage between 2-8°C to maintain their stability and efficacy. This temperature range is standard for monoclonal antibodies and helps preserve their biological activity.

Additional Storage Considerations

Beyond temperature, proper storage of OKT10 antibodies involves several important factors:

Light Protection: The antibody should be protected from prolonged exposure to light to prevent degradation.

Freeze-Thaw Cycles: It's recommended to use a manual defrost freezer and avoid repeated freeze-thaw cycles when storing antibodies.

Formulation: The OKT10 antibody is typically formulated in PBS at pH 7.2 with 0.09% sodium azide as a preservative and 0.2% BSA as a stabilizing agent.

For long-term storage, maintaining the 2-8°C temperature range is critical for preserving the antibody's binding capacity and overall performance in laboratory applications. The sterile packaging should remain intact until use to maintain sterility and prevent contamination.

Commonly Used Antibodies and Proteins with OKT10 in Research

OKT10 is a monoclonal antibody (mAb) clone targeting human CD38, a cell surface glycoprotein expressed on various immune cells, including mature lymphocytes, B cells, and lymphoplasmacytic cells. In research literature, OKT10 is noted for its role as a molecular tool and as a potential therapeutic agent, particularly in studies of B cell malignancies and acute lymphoblastic leukemia (ALL).

Frequent Partners in Immunotoxin Clinical/Translational Research

• HB2 (Anti-CD7): The most commonly cited partner for OKT10 in therapeutic studies is the HB2 antibody, which targets CD7, another surface antigen expressed on T cells and some B-cell malignancies. In the context of T-cell acute lymphoblastic leukemia (T-ALL), both OKT10 and HB2 have been conjugated to saporin (a ribosome-inactivating protein) to form immunotoxins—OKT10-SAPORIN and HB2-SAPORIN. These immunotoxins were tested both individually and in combination. The combination therapy showed superior efficacy compared to either single-agent treatment, likely due to the ability of the cocktail to target both CD7 and CD38, increasing the breadth of tumor cell targeting and potentially overcoming antigen heterogeneity.
• OKT10 itself as a reagent: OKT10 is also commonly used alone as a research reagent to probe CD38 expression in flow cytometry and histology, especially in studies of B cell maturation and malignancies.

Functional and Mechanistic Combination Studies

• Antibody-Dependent Cellular Cytotoxicity (ADCC): In preclinical models of T-ALL, the therapeutic effect of combining HB2-SAPORIN with unmodified OKT10 antibody (and the reverse combination) suggested an additive effect between direct saporin-mediated cytotoxicity (via the immunotoxin) and NK cell-mediated ADCC stimulated by Fc engagement with target-bound antibody.
• Native antibodies (non-conjugated): Both native OKT10 and HB2 antibodies showed modest but significant anti-leukemic effects in vivo, likely through ADCC mechanisms, but the combination of native antibodies did not produce an additive therapeutic benefit.

Summary Table: Common Partners for OKT10 in Literature

Overview

In summary, OKT10 is most frequently paired with the HB2 antibody (anti-CD7), either in native or saporin-conjugated ("immunotoxin") forms, for research and preclinical therapy of CD7/CD38-positive malignancies like T-ALL. The rationale for combining these agents is to increase the breadth and potency of anti-tumor effects by targeting multiple surface antigens, thus addressing the challenge of heterogeneous antigen expression in cancer populations.

Clone OKT10 is a mouse monoclonal antibody targeting CD38, a 45 kDa type II transmembrane glycoprotein that is highly expressed on certain immune cells and tumor cells. Key findings from scientific literature using clone OKT10 include:

• Cell and disease targeting: OKT10 binds strongly to CD38 expressed on plasma cells, activated T cells, and certain leukemic cells, but is less expressed on resting peripheral T cells.

• Therapeutic applications:

  • When conjugated with the radioisotope astatine-211 (^211At^), OKT10 can selectively bind and eradicate CD38? multiple myeloma cells in vitro and in mouse models. ^211At-OKT10 therapy extended survival and, at higher doses, cured mice of disseminated myeloma, significantly outperforming control groups in preclinical models.
  • As an immunotoxin conjugated with saporin (OKT10-SAPORIN), the antibody delayed the progression of human T-cell acute lymphoblastic leukemia (T-ALL) in SCID mouse models compared to controls, indicating a potent anti-tumor effect when used in targeted therapy.

• Immunophenotyping and cell biology:

  • OKT10 recognizes antigens present in resting thymocytes, plasma cells, null cells, monocytes, and bone marrow cells, and these antigens—such as CD38—are strongly upregulated on T cells upon activation. Experiments showed that OKT10 could reveal previously unexpressed cell surface antigen pools after membrane perturbation, suggesting antigen sequestration in resting cells until activation or antibody-induced crosslinking.

Summary of key insights:

• OKT10 is a highly specific anti-CD38 antibody instrumental in scientific research, especially for targeting CD38 in hematological malignancies and studying immune cell activation.
• Clinical potential is supported by its use in immunotoxins and radioimmunotherapy, with preclinical studies demonstrating significant anti-tumor efficacy in vivo.
• Biological findings include uncovering the mechanisms of CD38 antigen expression and its redistribution upon activation or antibody binding.

These findings establish clone OKT10 as a critical tool in immunology and cancer therapy research, particularly for CD38-targeted approaches and mechanistic studies of immune cell activation.