Anti-Human CD11b – Purified in vivo PLATINUM™ Functional Grade

Clone ICRF44 is a mouse monoclonal antibody that specifically binds to human CD11b (integrin alpha M, MAC-1, CR3), but is not reported to recognize the mouse homolog of CD11b. It is most commonly used for detecting and characterizing human CD11b-positive cells by flow cytometry and related in vitro methods, especially in human and nonhuman primate samples.

Key details about ICRF44 use:

• Species reactivity: ICRF44 is specific for human CD11b and cross-reacts with some nonhuman primates (e.g., baboon, rhesus, and cynomolgus monkeys), but it does not cross-react with mouse CD11b.
• Application: Used predominantly for in vitro analysis (e.g., flow cytometry staining of human blood or tissue samples).
• Functional effects: Has been reported to block adhesion and stimulate cytokine and chemokine release in human monocytes, and to inhibit leukocyte aggregation, but these functional effects have only been described in human systems.

In vivo mouse studies:
There is no evidence or manufacturer documentation supporting the use of ICRF44 for in vivo studies in mice, because it does not detect mouse CD11b. For studies involving CD11b in mice—including in vivo experiments and mouse immunophenotyping—researchers use anti-mouse CD11b antibodies (such as clone M1/70), not ICRF44.

Summary Table:

Conclusion:
ICRF44 is not used for in vivo mouse studies because it does not cross-react with mouse CD11b. Its use is limited to human (and some primate) samples, and predominantly for in vitro or ex vivo assays.

The correct storage temperature for sterile packaged clone ICRF44 (anti-human CD11b monoclonal antibody) is 2 to 8°C (refrigerated) and the antibody should be protected from prolonged exposure to light; it should not be frozen.

• For short-term storage and for antibodies supplied as ready-to-use solutions, maintain at 2–8°C as recommended by multiple manufacturers.
• Do not freeze, as freezing can denature the antibody or reduce its efficacy if not specifically formulated for long-term frozen storage.
• Keep the antibody protected from light to prevent degradation or loss of function if it is conjugated to a fluorophore.

Some suppliers offer reconstitution protocols for lyophilized antibodies (not commonly the case for this clone as a solution), in which case post-reconstitution, storage at 2–8°C is suitable for up to one month, and at -20°C for longer-term storage—but this does not apply to ready-to-use liquid products like "sterile packaged clone ICRF44". Always consult the product-specific datasheet for unique storage requirements.

Commonly used antibodies or proteins that are co-used with ICRF44 (anti-CD11b) in the literature typically target CD18, CD14, CD15, CD16, CD45, CD33, and other leukocyte or myeloid markers. These combinations are standard for phenotyping myeloid cells, such as monocytes, macrophages, neutrophils, and for distinguishing subsets within leukocyte populations.

Key points:

• ICRF44 specifically targets CD11b (integrin alpha M, part of Mac-1/CR3 complex). CD11b forms a heterodimer with CD18 (integrin beta 2), and together, these are essential for myeloid cell adhesion, activation, and phagocytosis.
• CD18: Routinely stained alongside CD11b to define the full Mac-1/CR3 complex and to differentiate between integrin subpopulations.
• CD14: Frequently used to identify monocytes and differentiate from other CD11b+ granulocytes.
• CD15, CD16: Used with ICRF44 for distinguishing between neutrophils (CD11b+CD15+) and monocytes (CD11b+CD14+).
• CD45: A pan-leukocyte marker, often used for general gating of leukocytes in multi-color panels.
• CD33: A myeloid marker frequently combined in panels to identify myeloid-derived suppressor cells (MDSCs) and other myeloid subsets.
• Other integrins and adhesion molecules (such as CD62L, CD49d, and ICAM-1): Sometimes used to explore cell adhesion and migration functions.

These marker combinations allow for comprehensive immunophenotyping, functional assays (e.g., adhesion, phagocytosis), and studies on immune cell activation, trafficking, and disease states—especially in inflammation, infection, and cancer contexts.

No single reference lists a standard cocktail, but these antibodies are repeatedly cited together in standard protocols and product datasheets for flow cytometry and single-cell applications.

Clone ICRF44 is a widely used monoclonal antibody targeting human CD11b (integrin ?M), with extensive citations in scientific literature focused on immunology and cell signaling. Key findings from studies citing ICRF44 include:

• Cell Surface Marker & Expression: ICRF44 binds the CD11b antigen, a 165–170 kDa glycoprotein known as integrin ?M, MAC-1, or CR3, expressed on human monocytes, granulocytes, natural killer (NK) cells, and some lymphocyte subsets.

• Functional Studies on Adhesion and Activation:

  • Binding of ICRF44 to CD11b blocks cell adhesion, reflecting the critical role of this integrin in cell–cell and cell–matrix interactions, particularly in leukocyte trafficking and recruitment to inflammatory sites.
  • ICRF44 is often used experimentally to stimulate cytokine and chemokine release from monocytes, demonstrating its utility in probing signaling mechanisms downstream of CD11b activation.

• Inflammation and Immune Response:

  • ICRF44 has been applied to dissect the importance of Mac-1 (CR3) clustering in triggering pro-inflammatory extracellular vesicle (EV) production by neutrophils (PMNs), with direct evidence that anti-CD11b (ICRF44) modulates innate immune cell behavior in inflammatory contexts.

• Flow Cytometry and Cell Identification:

  • Due to its specificity and strong binding, ICRF44 is a standard reagent in flow cytometry for the identification and quantification of CD11b-expressing cells in both basic research and clinical studies. Its cross-reactivity with primate species extends its application beyond humans.

• Citation Impact:

  • The ICRF44 antibody is cited in dozens of peer-reviewed publications (BioLegend lists 49), underscoring its reliability and broad adoption in studies concerning myeloid cell biology, innate immunity, and integrin function.

ICRF44’s major contributions in the literature include enabling precise identification of myeloid cells, mechanistic studies of leukocyte adhesion and migration, and insights into inflammatory signaling—making it a benchmark tool for research on human and primate immune function.