Anti-Rat Kappa Light Chain (Clone MAR 18.5) – Purified in vivo PLATINUM™ Functional Grade

Clone MAR 18.5 is primarily used in in vivo mouse studies as an anti-rat kappa light chain monoclonal antibody to target and deplete cells or antibodies of rat origin that have been administered to mice, and it is most commonly used as part of antibody depletion protocols, such as for depleting B cells or enhancing the depletion of neutrophils.

Key uses and essential context:

• B Cell Depletion: MAR 18.5 is used in combination with rat anti-mouse CD19 and CD22 (such as clones 1D3 and C?34.1) as part of in vivo B cell depletion protocols in mice. In these protocols, the primary rat monoclonal antibodies (anti-mouse CD19 and CD22) bind to B cells, and MAR 18.5 serves as a secondary antibody that recognizes the rat kappa light chain, facilitating enhanced depletion through mechanisms such as opsonization and Fc-mediated clearance.

• Enhancing Neutrophil/Cell Depletion: In models where a rat-origin primary antibody (e.g., anti-Ly6G for neutrophils) is used for cell depletion, MAR 18.5 can be administered after the primary antibody to increase the removal of antibody-bound target cells or to mask residual antibody, thereby allowing assessment of antigen bioavailability and the effectiveness of depletion. This is achieved because MAR 18.5 binds to the rat kappa light chain present on the surface-bound primary antibody, promoting more effective immune clearance.

• Mechanistic Role: MAR 18.5 works because it is a mouse IgG2a antibody that binds specifically to the rat kappa light chain (both RI-1a and RI-1b allotypes). This specificity allows it to interact with any rat-derived immunoglobulin administered into the mouse, thus acting as a reliable cross-linker or depletion facilitator in immunological studies.

• Other Applications: Beyond depletion, MAR 18.5 is also used for ELISA, ELISPOT, flow cytometry, immunofluorescence, immunohistochemistry, and Western blotting when targeting rat kappa light chain in mouse models.

• Typical Dosing: Protocols vary, but one published protocol uses 50??g per mouse for anti-rat kappa (MAR 18.5), often i.p. (intraperitoneally), following or together with the primary rat antibody.

In summary, MAR 18.5 is an essential reagent for in vivo mouse studies requiring the targeting, depletion, or detection of rat immunoglobulins—most notably for synergistic depletion of mouse B cells when used alongside rat anti-mouse antibodies, or for accelerating the clearance of cell populations labeled with rat monoclonal antibodies.

The correct storage temperature for a sterile-packaged DNA clone such as "clone MAR 18.5" depends on its formulation—whether it is shipped dried or resuspended in buffer:

• For dried DNA:

  • Room temperature (up to 3 months)
  • 4°C (up to 12 months)
  • -20°C (up to 24 months)
  • -80°C (for long-term storage)

• For resuspended DNA:

  • Room temperature (up to 3 months)
  • 4°C (up to 12 months)
  • -20°C (up to 24 months)
  • -80°C (for long-term storage)

Best practices recommend storing resuspended or hydrated DNA at -20°C or -80°C for maximum stability and shelf life, and to avoid repeated freeze/thaw cycles by using aliquots.

If your clone is packaged in a sterile dry format, room temperature is sufficient for short-term storage, but for long-term preservation, store at -20°C or -80°C.

If there are specific manufacturer guidelines included with your clone, follow those as they take precedence. For all synthetic genes and gene fragments, the above conditions maintain integrity and sterility.

Commonly Used Antibodies and Proteins with MAR 18.5 in Research Literature

MAR 18.5 is a monoclonal antibody specific for rat kappa immunoglobulin light chain, and its use is often described in the context of cell depletion, functional assays, and cell surface labeling in immunology research. While the literature directly referencing MAR 18.5 is somewhat sparse, a few notable combinations and applications have been documented.

Combination Antibodies for Cell Depletion

• Anti-CD19 and Anti-CD22: MAR 18.5 has been used in combination with anti-CD19 and anti-CD22 for in vivo B cell depletion in mice. This approach takes advantage of targeting both kappa light chains (MAR 18.5) and B cell–specific surface markers (CD19, CD22) to achieve more effective B cell removal.
• T Cell Isolation and Complement Lysis Markers: MAR 18.5 has been used alongside J11d.2 (anti-heat-stable antigen), 2.43 (anti-CD8), M5/114 (anti-major histocompatibility complex class II), and 2.4G2 (anti-Fc? receptor) for T cell isolation and complement-mediated lysis procedures. These combinations are typical in protocols for isolating specific lymphocyte populations or for depleting unwanted cells from a mixture.
• Rat Anti-Fc?R (2.4G2): In studies of Fc? receptor-mediated phagocytosis, MAR 18.5 was used as a secondary cross-linking antibody during stimulation of macrophages treated with supernatant from the rat anti-Fc?R hybridoma (clone 2.4G2). This highlights its utility in functional assays beyond simple detection.

Supporting Proteins in Functional Assays

• Protein A: MAR 18.5, being an IgG2a kappa isotype, binds strongly to protein A, which is commonly used for antibody purification and in some assay formats.
• Complement: In protocols involving complement-mediated lysis, complement proteins are used in conjunction with MAR 18.5 and other surface marker antibodies to selectively lyse target cells.

Other Contexts

While MAR 18.5 is not directly associated with the commonly used mismatch repair protein antibodies (MLH1, PMS2, MSH2, MSH6) in cancer diagnostics, these are highlighted in the literature for DNA repair deficiency studies, but not in combination with MAR 18.5. Similarly, antibodies like anti-Ly6G or anti-Gr1 used for neutrophil depletion in mice have not been reported in combination with MAR 18.5 in the provided literature.

Summary Table: Common MAR 18.5 Combinations

Conclusion

MAR 18.5 is most frequently co-used with antibodies against B cell–specific markers (CD19, CD22), T cell and antigen-presenting cell markers (J11d.2, 2.43, M5/114, 2.4G2), and in functional assays involving Fc? receptors (2.4G2) and complement. These combinations are standard in immunological protocols for cell depletion, isolation, and functional characterization, but MAR 18.5 is not typically paired with antibodies used in other fields (e.g., cancer DNA repair).

Based on the available scientific literature, clone MAR 18.5 has been primarily utilized in neutrophil depletion studies and B cell depletion research, with several key findings emerging from its applications.

Primary Applications and Mechanisms

Clone MAR 18.5 is a monoclonal antibody that specifically targets the kappa chain of rat immunoglobulin light chain. This antibody has found particular utility in immunological research where precise cell depletion is required for experimental purposes.

Key Research Findings

Enhanced Neutrophil Depletion Protocol

The most significant finding involves MAR 18.5's role in developing a more effective neutrophil depletion strategy. Researchers discovered that combining anti-Ly6G antibodies with MAR 18.5 creates a "Combo" approach that achieves durable and controlled neutrophil depletion in mice. This combination protocol demonstrated superior efficacy compared to anti-Ly6G treatment alone, particularly in challenging experimental conditions such as older C57BL/6 mice.

The research revealed that mice treated with the anti-Ly6G + MAR 18.5 combination had increased Ly6G antigen availability compared to controls, suggesting that MAR 18.5 helps overcome antigen masking issues that typically limit the effectiveness of single-antibody depletion strategies.

Overcoming Antigen Masking

A critical finding relates to addressing the antigen masking problem in cell depletion studies. When antibodies are used for in vivo depletion, they often prevent subsequent detection of target cells by blocking surface antigens. The MAR 18.5 combination approach helps mitigate this limitation, allowing for more accurate assessment of depletion efficacy.

B Cell Depletion Applications

MAR 18.5 has also been employed in B cell depletion protocols, where it works synergistically with rat anti-mouse CD19 and CD22 antibodies (clones 1D3 and C?34.1) to achieve effective B cell elimination in vivo.

Methodological Advances

The research utilizing MAR 18.5 has contributed to important methodological improvements in immunological studies. The development of intracellular Ly6G staining techniques, validated through MAR 18.5 combination studies, provides researchers with more reliable methods for detecting neutrophils even after depletion treatments.

These findings collectively demonstrate that MAR 18.5 serves as a crucial tool for enhancing the specificity and durability of immune cell depletion protocols, particularly addressing long-standing challenges in neutrophil depletion research where single-antibody approaches often prove insufficient.