Clone B7/21 is a monoclonal antibody that specifically recognizes a monomorphic epitope on human HLADP molecules, predominantly used in flow cytometry and related applications to analyze human cells. There is no evidence in the provided search results that B7/21 is used directly for in vivo mouse studies.

Key context and application details:

• Species specificity: B7/21 targets multiple human HLADP isotypes (DP1, DP2, DP3, DP4, DP5) and does not crossreact with the mouse MHC class II equivalents, such as IA or IE. Therefore, it is not suitable for targeting murine MHC molecules in mouse models.
• Typical use: The antibody is routinely used to stain human leukocytes (especially antigenpresenting cells) in flow cytometric analysis, helping to assess human HLADP expression after transplantation or in humanized mouse models containing human immune cells.
• Recombinant forms: Modern versions use human IgG1 constant regions to enhance downstream applications, but their specificity for human HLADP remains unchanged.
• In vivo mouse studies: The only possible in vivo mouse application would be in “humanized mouse” models, where mice are engrafted with human immune cells or tissues expressing HLADP. In these cases, B7/21 could be employed postmortem to identify and characterize human cells within mice, but not to manipulate or track murine cells themselves.

Summary Table: Specificity and In Vivo Use of B7/21

If your aim is to study MHC class II molecules in murine models, you should use antibodies specific to mouse MHC II (e.g., antiIA, antiIE clones). Clone B7/21 is not appropriate for direct immunological studies in mice unless the mice contain human cells expressing HLADP.

Commonly used antibodies or proteins paired with B7/21 (which targets HLADP, a human MHC Class II antigen) in the literature often include other MHC Class II antibodies and markers for immune cell characterization. The most frequent combinations are:

• HLADR and HLADQ antibodies: Since B7/21 is highly specific for HLADP and does not react with HLADR or HLADQ, studies often use antiHLADR and antiHLADQ antibodies alongside B7/21 to distinguish between different MHC class II molecules on the cell surface or tissue sections.

• CD markers (e.g., CD4, CD8, CD14, CD19): These antibodies are frequently used to identify immune cell types expressing or presenting HLADP. For example, CD4 identifies helper T cells, CD19 marks B cells, and CD14 marks monocytes/macrophages—all of which can express MHC class II antigens, including HLADP.

• Other B7 family proteins: Research regularly employs antibodies against PDL1 (B7H1), B7H3, and related costimulatory molecules to examine their roles in immune modulation and tumor immunology, particularly in the context of cancer studies or immune checkpoint exploration. For instance, B7H3 is frequently studied in combination with CD3 (T cell marker) and Fcmodified antibodies for functional assays or therapeutic applications.

• Treg and T cell activation markers: In studies involving immune regulation or tumor immunity, antibodies against CD25 (a Treg marker), CTLA4, and related proteins are used alongside B7 molecules to evaluate immune cell activation or suppression. For example, combining B7Fc fusion proteins (such as B7.1Fc) with antiCD25 (PC61) is a common approach in tumor immunotherapy animal models.

The exact combination depends on the experimental or clinical context—such as flow cytometry panels, immunohistochemistry, or functional immune assays. The use of switchvariant B7/21 (IgG1 vs. IgG3) is another detail sometimes explored for blocking or crossblocking experiments in studies of HLADP specificity.

In summary, antiHLADR, antiHLADQ, immue celltype markers (CD4, CD8, CD14, CD19), and various cosignaling molecule antibodies (PDL1, B7H3, CD25, CTLA4) are most commonly used in conjunction with B7/21 in the literature.

Clone B7/21 is a wellestablished monoclonal antibody that specifically recognizes a monomorphic epitope on human HLADP and is widely used in immunological studies to identify or block HLADP molecules. Key findings from scientific literature citing clone B7/21 include:

• Specificity: Clone B7/21 binds specifically to human HLADP1, DP2, DP3, DP4, and DP5, but it does not crossreact with other MHC class II molecules such as HLADR or HLADQ. This makes it valuable for distinguishing HLADP from other MHC class II proteins in experimental settings.

• Applications:

  • It is widely used in flow cytometry, immunoprecipitation, and blocking studies to study the distribution, structure, and function of HLADP on various cell types, especially professional antigenpresenting cells (APCs) like B cells, dendritic cells, and macrophages.
  • The antibody can aid in examining conditions and mechanisms involving HLADP presentation, such as Tcell responses, transplantation compatibility, and some autoimmune disease contexts.

• Role in Research on Class II MHC Functions: Clone B7/21 is often utilized in mechanistic studies to define the contribution of HLADP to antigen presentation and to differentiate responses mediated via DR, DQ, or DP molecules. In one cited immunological study, B7/21 was used to show that certain T cell clones were not activated via classical DR, DQ, or DP molecules, suggesting the presence of novel class IIlike molecules; here, B7/21 was used specifically to rule out HLADP as the relevant stimulating determinant.

• Engineering and Improvements: Recombinant versions of B7/21 have been developed, often switching the constant region from mouse IgG3 (which tends to precipitate) to human IgG1 for improved performance and compatibility with human systems in research and potential clinical use.

There is no evidence in these results that clone B7/21 is associated with functional signaling upon binding (i.e., it does not appear to modulate HLADP function, but serves rather as a blocking or detection reagent).

Accordingly, the key scientific contributions of clone B7/21 are its robust specificity for HLADP and its broad experimental utility in immunology for distinguishing or functionally interrogating HLADP in both basic and translational research.

Dosing regimens for clone B7/21, a monoclonal antibody targeting human HLADP antigens, are not specifically outlined for in vivo mouse studies in publicly available dosing guides or experimental reports. The details available primarily describe its specificity and applications (e.g., immunocytochemistry on human cells), but do not provide mouse dosing schedules, routes, or variations across different mouse models.

Essential context:

• The B7/21 monoclonal antibody is designed to recognize human HLADP molecules and is most commonly used for in vitro assays, such as immunocytochemistry (ICC), flow cytometry, or cell sorting on human samples or humanized cell lines. It does not crossreact with mouse antigens because the recognized determinants are specific to the human HLADP isoforms.
• There is no evidence from current antibody dosing guides that B7/21 is used for in vivo mouse models, nor do established mouse model dosing guides list regimens for this clone. Most dosing regimens for monoclonal antibodies in mice (e.g., antiPD1, antiCD4) typically fall in the 100–250 µg per mouse, administered intraperitoneally 23 times per week, but these are for antibodies against murine antigens.

Additional relevant information:

• Dosing regimens may vary widely depending on pharmacokinetics, disease model, antigen expression, and study purpose (e.g., depletion, blocking, or detection).
• For monoclonal antibodies used in preclinical mouse studies, initial starting doses generally range from 115 mg/kg. However, this is not directly translatable to B7/21, as it is intended for recognizing human, not murine, targets.
• If B7/21 were used in a humanized mouse model (expressing human HLADP), it would be critical to optimize dose, route, and schedule empirically due to variability in antigen expression and host immune responses. No published data currently detail such regimens for B7/21.

In summary, there are no standardized or published dosing regimens for B7/21 across mouse models. Its use is limited to assays with human cells, and any adaptation for in vivo mouse studies (such as humanized mice) would require casespecific pilot dosing.