Anti-Human CD68 (Clone KP1) – Purified No Carrier Protein

Clone KP1 is an anti-human CD68 monoclonal antibody with specific applications in in vivo mouse studies. Its primary use focuses on immunohistochemical staining of human macrophages or monocytes in xenograft models, where human cells are engrafted into mice, such as studies on humanized mice or tumor xenografts.

Applications in Xenograft Models

The clone is particularly valuable for researchers working with mouse models that contain human cells. In these experimental settings, KP1 enables the identification and characterization of human macrophages and monocytes that have been introduced into the mouse system. This specificity for human CD68—a 110 kDa glycoprotein predominantly expressed on intracellular lysosomes of monocytes and macrophages—makes it an essential tool for distinguishing human immune cells from murine cells in mixed populations.

Technical Considerations

For in vivo mouse studies, clone KP1 is typically used in functional grade purified formats without carrier proteins, which ensures compatibility with the stringent requirements of in vivo research. The antibody recognizes human CD68 and shows cross-reactivity with primate and rat species, though its primary utility in mouse models remains focused on detecting human cells rather than mouse cells.

The typical applications include immunohistology on paraffin-embedded tissues, immunofluorescence, flow cytometry, and western blotting of human cells within mouse tissues, allowing comprehensive analysis of human macrophage populations and their distribution in various experimental contexts.

Other commonly used antibodies and proteins that appear alongside KP1 (anti-CD68) in the scientific literature serve to identify and distinguish various immune cell populations, particularly within the monocyte/macrophage lineage and related cell types.

Monocyte/Macrophage Markers

The most frequently paired antibodies include CD14, CD163, and CD11b, which are markers specifically used for identifying cells within the monocyte/macrophage lineage. These markers help researchers comprehensively characterize macrophage populations and distinguish between different activation states or subpopulations of these immune cells.

Context-Dependent Selection

The choice of antibody combinations used with KP1 is highly context-dependent and tailored to specific research needs. Scientists select these combinations based on several objectives:

Distinguishing immune cell types - Different antibody panels help differentiate between macrophages and other immune cells present in tissues

Diagnosing hematopoietic neoplasms - Specific marker combinations aid in identifying and classifying blood cell cancers

Characterizing tissue environments - Antibody panels help analyze inflammation patterns and tumor microenvironments, particularly when studying tumor-associated macrophages

The specific combinations chosen depend on whether researchers are working with normal tissues, diseased tissues (such as rheumatoid arthritis or osteoarthritis), various neoplasms, tumor cell lines, or specialized models like human tumor xenografts in mice. In xenograft studies, KP1 is particularly valuable because it specifically delineates the human myeloid compartment against the murine background, allowing precise identification of human-derived macrophages.

Clone KP1 represents a significant monoclonal antibody in immunohistochemistry and macrophage research, with key findings spanning several decades of scientific investigation. This antibody has become a fundamental tool for identifying and studying cells of the monocyte/macrophage lineage in both normal and diseased tissues.

Antibody Characteristics and Specificity

KP1 was developed by immunizing BALB/c mice against a lysosomal fraction of human lung macrophages. The antibody recognizes CD68, a heavily glycosylated type I transmembrane glycoprotein belonging to the lysosomal-associated membrane protein (LAMP) family. A defining characteristic of KP1 is its recognition of a fixation-resistant epitope, which allows it to be used effectively on routinely processed, paraffin-embedded tissue sections. This epitope is likely glycan-based and recognizes a molecule of approximately 110 kilodaltons in macrophage-rich human tissue.

Cellular Reactivity and Distribution

KP1 demonstrates broad reactivity with cells of the mononuclear phagocytic lineage, staining tissue macrophages including Kupffer cells, germinal centre macrophages, splenic macrophages, and lamina propria macrophages. The antibody also reacts with granulocyte precursors. CD68 localizes predominantly to lysosomal membranes, with a small amount present on the cell surface, and can be found in the cytoplasm of monocytes/macrophages, fibroblasts, human peripheral blood lymphocytes, neutrophil primary and mast cell granules, large granular lymphocytes, basophils, and various other cell types.

Importantly, while KP1 was originally used as a pan-monocytic/macrophage marker, CD68 is not macrophage-specific, and KP1 is known to stain neutrophils and other non-macrophage-like cells. Interdigitating reticulum cells show limited or no staining, while Langerhans' cells and follicular dendritic reticulum cells remain unreactive.

Clinical and Diagnostic Applications

KP1 has proven valuable for studying disorders of the monocyte/macrophage system, including both reactive and neoplastic states such as true histiocytic proliferations. The antibody reacts with CD68 in a wide range of healthy and disease-associated tissues, including those from patients with rheumatoid arthritis and osteoarthritis, as well as various neoplasms, tumor cell lines, and tumor-associated macrophages.

In hematological malignancies, KP1 shows specific staining patterns that aid in diagnosis. It labels acute leukemias of M4 and M5 types and rare examples of malignant histiocytosis/true histiocytic sarcoma. The antibody shows strong granular cytoplasmic staining in chronic and acute myeloid leukemia and reacts with rare cases of true histiocytic neoplasia.

Comparative Advantages

When compared to other macrophage markers, KP1 offers distinct advantages. The PG-M1 antibody, another CD68 antibody, showed more restricted reactivity with elements of the monocyte/macrophage lineage than KP1 in routine paraffin sections. Unlike PG-M1, which detects a macrophage-restricted form of the CD68 antigen, KP1 reacts with both macrophages and myeloid cells. This broader reactivity makes KP1 particularly useful for comprehensive studies of the mononuclear phagocytic system across different tissue types and pathological conditions.

Dosing regimens of clone KP1 (anti-human CD68) primarily depend on the application and mouse model; most commonly, KP1 is used for immunostaining with a fixed dilution (typically 1:200) in humanized mouse models, whereas in vivo functional or gene transfer applications may use a defined titer or dose per weight.

Key regimens reported include:

• Immunostaining (especially in humanized models):

  • Dilution: 1:200
    This is the standard regimen in humanized hepatocellular carcinoma (HCC) mouse models for histological or flow cytometric staining to identify human macrophages or monocytes.
  • Common mouse model: Humanized liver models, neonatal FRG (Fah−/−/Rag2−/−/Il2rg−/−) mice transplanted with human hepatic and non-parenchymal cells.

• In vivo gene transfer using AAV vectors expressing KP1 (not the antibody, but AAV-KP1 vector):

  • Dose: 1.0 × 10¹³ vector genomes per kg (vg/kg)
    Used for systemic or targeted gene delivery, as in C57BL/6J mice, with intravenous (IV), retro-orbital (RV), or renal pelvis (RP) administration. This context refers to the gene construct “AAV-KP1” rather than direct KP1 antibody administration.

• Fluorochrome-conjugated KP1 for tissue staining:
  Again, the 1:200 dilution is typical, supporting reproducibility across research settings for immunohistochemistry.

• No evidence was found in the provided results for in vivo depletion or functional modulation regimens (such as those used for checkpoint or cell depletion antibodies). Most in vivo dosing regimens (e.g., 100-250 μg/mouse) seen in antibody guides refer to other clones and targets, not KP1.

Summary table:

*Note: "AAV-KP1" refers to an adeno-associated virus vector and not the anti-CD68 antibody itself.

Essential context:

• KP1 is almost exclusively used in research to detect human CD68+ cells (macrophages/monocytes) in chimeric or humanized mouse tissues.
• Direct in vivo functional dosing (e.g., depletion or therapeutic modulation) is not a typical use for KP1, unlike other antibodies targeting mouse-specific markers.
• For other dosing regimens with unrelated antibodies (e.g., anti-Ly6G, anti-PD-1), refer to reference guides as these typically do not apply to KP1.

If searching for dosing regimens for KP1 outside immunostaining (for in vivo intervention or functional studies), current literature and commercial protocols do not indicate standard dosages. For more specialized uses, dose selection may require empirical optimization.