Anti-Human CD11b - Purified in vivo GOLD™ Functional Grade

The clone ICRF44 is a mouse monoclonal antibody specific for human CD11b, a glycoprotein also known as integrin alpha M, Mac1, or CR3. While it is primarily used for detecting CD11bexpressing cells in human samples, its use in mice typically involves models that incorporate human immune systems, such as humanized mice. These models are designed for preclinical testing of immunotherapies or for studying human immune responses in vivo.

Common applications of clone ICRF44 in the context of humanized mice or in vivo studies include:

• Immunotherapy Testing: Clone ICRF44 can be used to study the effects of immunotherapies on human immune cells in vivo, particularly in models where human tumors are grown in immunodeficient mice.

• Detection and Functional Studies: Although primarily used for flow cytometry and immunohistochemistry in human samples, clone ICRF44 can be used to monitor CD11b expression and function in humanized mice, helping to understand how human immune cells interact in a murine environment.

• Preclinical Models: While not directly mentioned, clone ICRF44 might be utilized in preclinical models to study the role of CD11b in inflammation and immune responses within a humanized environment, given its role in cell adhesion and immune cell function.

There is limited specific information on the direct in vivo applications of clone ICRF44 in mice. However, its utility in studying human immune responses in humanized models suggests potential applications in preclinical research related to immunotherapy and immune function.

Based on the search results, antiCD18 antibodies are frequently used alongside ICRF44 to assess the expression and function of the complete Mac1 complex. This makes biological sense because CD11b (which ICRF44 targets) associates noncovalently with integrin beta2 (CD18) to form the CD11b/CD18 heterodimeric complex, also known as Mac1 or CR3.

Functional Context

The CD11b/CD18 complex serves as a receptor for multiple ligands that are critical for cellcell and cellmatrix interactions. These ligands include ICAM1 (CD54), ICAM2 (CD102), ICAM3 (CD50), and ICAM4 (CD242), as well as CD14, CD23, iC3b, fibrinogen, heparin, and Factor X. Studies examining these adhesion interactions would naturally employ antibodies or proteins targeting these molecules alongside ICRF44.

The ICRF44 antibody is expressed on monocytes, granulocytes, activated lymphocytes, a subset of NK cells, dendritic cells, and microglia in the brain. Given this expression pattern, researchers studying immune cell function often use ICRF44 in conjunction with markers for these specific cell populations to characterize CD11bpositive subsets within complex immune cell mixtures.

Clone ICRF44 is a widely used monoclonal antibody targeting human CD11b (integrin αM, MAC1, CR3), and key findings from its scientific citations highlight its utility in immunology and cell biology research.

Key findings from scientific literature citing ICRF44:

• Specificity & Cellular Expression:
  ICRF44 specifically detects CD11b, a 165 kDa glycoprotein primarily expressed on monocytes, granulocytes, NK cells, and some peripheral blood lymphocytes. Its staining has been critical in distinguishing myeloid cells and subsets in human samples, including blood and tissue leukocytes.

• Functional Effects:
  ICRF44 has been shown to block adhesion functions of CD11b, especially during granulocyte response to inflammatory stimuli (such as fMLP), and inhibits heterotypic adhesion. It can also stimulate monocyte activation leading to the release of cytokines and chemokines.

• Immunophenotyping Utility:
  The antibody is extensively validated for flow cytometry, immunofluorescence, and other immunological assays for identifying and quantifying CD11b+ populations, including monocytes, granulocytes, activated lymphocytes, and NK cells in research and clinical settings.

• Mechanistic Studies:
  Studies using ICRF44 have helped demonstrate the role of CD11b/Mac1 clustering in triggering proinflammatory responses. For instance, it was used to study Mac1 receptor clustering and downstream extracellular vesicle production in human polymorphonuclear leukocytes (PMNs). It is also used to block or track intracellular signaling involving ICAM family members and complement components (such as iC3b), underscoring CD11b’s role in cell–cell and cell–matrix interactions.

• Preclinical and Clinical Research:
  ICRF44 is referenced in studies on immunosuppressive cell populations in cancer, inflammation, and infection, highlighting its utility in profiling myeloidderived suppressor cells and assessing immune responses in disease models.

• CrossReactivity:
  While highly specific to human CD11b, ICRF44 also shows some crossreactivity with related primate species (baboon, chimpanzee, cynomolgus monkey, rhesus monkey, pig), but notably does not recognize mouse CD11b.

Summary of typical applications cited in key literature:

• Immunophenotyping of human myeloid and NK cells
• Blocking CD11bmediated adhesion and migration
• Functional assays on cytokine release and cell activation
• Imaging of CD11b distribution and clustering
• Preclinical studies of immune cell roles in disease

ICRF44’s frequent citation reflects its reliability and specificity for human CD11b, making it a standard tool in studies of leukocyte biology, inflammation, and immunemediated disease.

Dosing Regimens of Clone ICRF44 in Mouse Models

Nature and Use of Clone ICRF44

Clone ICRF44 is a mousederived monoclonal antibody that specifically recognizes human CD11b, a cell surface glycoprotein expressed on monocytes, granulocytes, NK cells, and some peripheral blood lymphocytes. Its primary applications are in vitro—including flow cytometry, immunofluorescence, and functional assays—rather than in vivo use in mouse models. Importantly, ICRF44 is reactive with human and some nonhuman primate CD11b, but not with mouse CD11b.

In Vivo Use in Mouse Models

Published Dosing Regimens

There is no single, published, or standardized dosing regimen for clone ICRF44 across different mouse models. The antibody is typically used as a tool for in vitro detection and functional studies of human CD11b, not for modulating mouse immune cells in vivo. In vitro applications include blocking heterotypic adhesion, granulocyte activation, and PMN aggregation, but these are not in vivo dosing scenarios.

CrossReactivity and Species Limitations

Because ICRF44 targets human CD11b and has limited crossreactivity with certain nonhuman primates (e.g., cynomolgus monkey, baboon, rhesus monkey), it is generally not suitable for dosing regimens in mouse models where the target is mouse CD11b. There is no evidence in the available literature that ICRF44 is used for in vivo administration in wildtype mice, as it does not bind to mouse CD11b. Any in vivo dosing of ICRF44 in mice would likely be in the context of humanized mouse models, where engrafted human cells express human CD11b—these studies are rare and would require custom optimization.

Optimization and Custom Use

If in vivo use in humanized mouse models is attempted, dosing regimens would need to be empirically determined, taking into account the specific experimental model, the expression levels of human CD11b, and the desired biological effect (e.g., blocking adhesion, stimulating cytokine release). No published protocols or standard doses are available for such scenarios.

Summary Table: ICRF44 in Mouse Models

Conclusion

There is no established or widely published dosing regimen for clone ICRF44 in mouse models, primarily because the antibody is designed for human and select primate CD11b, not mouse CD11b. Its use is almost exclusively in vitro for human cells or in humanized mouse models, in which case dosing would be experimental and require custom optimization. For wildtype mouse models, ICRF44 is not appropriate as a therapeutic or investigative agent due to speciesspecific reactivity.