KK3 — anti-CD73/NT5E for the ecto-5′-nucleotidase of the adenosine axis in human FFPE IHC.

KK3 is a mouse monoclonal antibody (IgG2b/κ) raised against a peptide of human CD73, the GPI-anchored ecto-5′-nucleotidase encoded by the gene NT5E. The immunogen region and the epitope are not published. It is offered as a research reagent for immunohistochemistry on human formalin-fixed, paraffin-embedded (FFPE) tissue with a membranous staining pattern.

DIA-KK3 is the ONCOdianova catalog number of the anti-CD73 antibody clone KK3: mouse monoclonal (IgG2b/κ), reactivity human, IHC on FFPE tissue, lyophilized, reconstituted to 500 µl, tonsil as positive control. The distributor catalog number at BIOZOL is ODN-DIA-KK3. For research use only.

Yes. The datasheet states that clone KK3 was developed and validated specifically for the immunohistochemical detection of CD73 in routine FFPE human tissue specimens, gives a starting range of 1:100 to 1:200 and separate dilutions for biotin/(strept)avidin-based (1:50) and polymer-based detection (1:150). The previous ONCOdianova product page documents a manual autoclave protocol, and ten original ONCOdianova figures show CD73 staining in tonsil, placenta and eight tumor tissues.

The datasheet gives 1:100 to 1:200 as a general recommendation for IHC on FFPE sections and, in the instructions for use, 1:50 for biotin/(strept)avidin-based detection (e.g. ABC-HRP/AEC) and 1:150 for polymer-based detection (e.g. Dako EnVision, peroxidase/DAB). The manual protocol of the previous product page uses 1:150 with 60 min at 37 °C. Dilution, retrieval, incubation and detection belong together; each laboratory establishes its own conditions.

Heat-induced epitope retrieval is required. The datasheet recommends pretreatment in an autoclave at pH 7.8 (Tris-EDTA-citrate, e.g. TEC buffer); the manual protocol of the previous product page specifies 121 °C for 5 min in TEC buffer, pH 7.8.

Tonsil is the positive control named in the datasheet; the expected visualization is membranous. The ONCOdianova figures show membranous CD73 staining of tumor cells in cholangiocellular carcinoma (strong, homogeneous), hepatocellular carcinoma (heterogeneous), adenocarcinoma of the lung (apical predominance), squamous cell carcinoma of the lung (strong, diffuse), malignant melanoma and angiosarcoma, staining of the superficial membrane of the placental syncytiotrophoblast, and CD73 staining of lymphocytes in a Warthin tumor of the parotid gland.

Tonsil. It is the positive control tissue named in the KK3 datasheet, and a tonsil figure is part of the documented ONCOdianova image material.

The datasheet documents a membranous visualization. In the ONCOdianova figures the membranous CD73 staining is tissue-specific — for example strong and homogeneous in a cholangiocellular carcinoma, heterogeneous in a hepatocellular carcinoma and with apical predominance in an adenocarcinoma of the lung.

Yes — the KK3 datasheet documents membranous visualization, consistent with CD73 being a GPI-anchored cell-membrane enzyme. The documented patterns are tissue-specific and include apical predominance and heterogeneous membranous staining; they are not a claim of uniform membranous staining in all tissues.

No. Immunohistochemistry demonstrates the presence and localization of the CD73 protein; it does not measure the enzymatic conversion of AMP to adenosine, local adenosine concentrations or an immunosuppressive effect. Statements on enzyme activity require separate assays.

CD73 is expressed by many cell types. In the published literature it is described on tumor cells, on cancer-associated fibroblasts and stromal cells, on endothelium and on lymphocyte subsets, and it occurs in normal epithelial and lymphoid tissues; the ONCOdianova figures show tumor cells, syncytiotrophoblast and lymphocytes. Tumour, stromal, endothelial and immune-cell staining should therefore be evaluated separately and, where the research question requires it, with additional markers.

Clone KK3 was developed and validated specifically for the immunohistochemical detection of CD73 in routine FFPE human tissue specimens, with a documented protocol and figures from tonsil, placenta and eight tumor tissues; it is highly efficient for CD73 detection in normal and tumor FFPE tissue.

DIA-KK3 is a lyophilized antibody purified from culture supernatant, reconstituted to 500 µl with sterile distilled water; the previous product page states 20 µg per vial. The datasheet gives the formulation as PBS, pH 7.4, with 1% BSA and 0.05% sodium azide. Store lyophilized at 2–8 °C, long term at −20 °C; reconstituted at 2–8 °C for several weeks; avoid repeated freeze/thaw cycles.

NT5E is the human gene (chromosome 6q14.3, NCBI Gene 4907) encoding ecto-5′-nucleotidase, the cell-surface enzyme known by its CD name CD73. Clone KK3 detects the CD73 protein encoded by NT5E in human FFPE tissue; it does not detect the gene or transcript.

Yes. CD73 is the protein name of ecto-5′-nucleotidase (5′-nucleotidase ecto), encoded by the human NT5E gene on chromosome 6q14.3 (NCBI Gene 4907); further aliases are eN, eNT, NT5 and E5NT. UniProt entry P21589 describes the 574-amino-acid GPI-anchored cell-membrane enzyme.

Ecto-5′-nucleotidase is the enzyme name of CD73 (gene NT5E): a GPI-anchored cell-surface enzyme that hydrolyses extracellular AMP to adenosine. Its membrane localization is the basis of the membranous CD73 staining pattern in IHC.

CD73 and NT5E denote the same target — the NT5E gene encodes the CD73 protein. The ONCOdianova antibody for the immunohistochemical detection of this target in routine human FFPE tissue is clone KK3 (DIA-KK3). KK3 detects the protein; it does not detect the NT5E gene or transcript, and no superiority over other CD73 antibodies is claimed.

CD39 (ENTPD1) and CD73 (NT5E) are two distinct ectonucleotidases of the extracellular ATP–adenosine pathway: CD39 converts ATP and ADP to AMP, and CD73 hydrolyses AMP to adenosine. Clone KK3 detects CD73 only; it does not detect CD39. Statements about the pathway describe target biology, not properties of the antibody.

CD73 hydrolyses extracellular AMP to adenosine and thereby forms, together with CD39, the extracellular ATP–adenosine pathway. Adenosine is described in the published literature as an immunosuppressive mediator in the tumor microenvironment, and CD73 is discussed as a target of the adenosine checkpoint in immuno-oncology research. These statements describe target biology; they are not performance evidence for clone KK3, and CD73 IHC does not measure adenosine or enzyme activity.

CD73 IHC is being investigated in the context of adenosine-targeted therapy and patient stratification research. Clone KK3 is a research reagent in this field; it is not a validated predictive biomarker or companion diagnostic and carries no claim on therapy selection or treatment response.

The suitability of a clone depends on the application and must be validated in the user’s laboratory. ONCOdianova clone KK3 was developed and validated specifically for the immunohistochemical detection of CD73 in routine FFPE human tissue specimens, with membranous visualization, tonsil as positive control, a documented manual protocol and original figures from tonsil, placenta and eight tumor tissues. No superiority over other CD73 clones is claimed.

In the documented ONCOdianova figures, the CD73 staining pattern with clone KK3 is tissue-specific: strong and homogeneous membranous staining in a cholangiocellular carcinoma, heterogeneous staining in a hepatocellular carcinoma, apical predominance in an adenocarcinoma of the lung, strong diffuse staining in a squamous cell carcinoma of the lung, prominent staining in a malignant melanoma and strong staining in an angiosarcoma. These are documented individual fields, not a general expression map; tumor-cell, stromal and immune-cell staining should be evaluated separately.

The current datasheet of anti-CD73 clone KK3 (DIA-KK3), version 25 February 2025, is available as a PDF download in the Documents section of this page. Its product content is identical to the version of 22 February 2022; the update concerns the distribution address. The datasheet documents identity, immunogen, formulation, reconstitution, storage, the IHC starting range with detection-system-dependent dilutions, epitope retrieval, tonsil as positive control, the membranous staining pattern and four figures.

No. KK3 is intended for research use only and is not intended for diagnostic or therapeutic procedures. Statements on patient selection, therapy response or prognosis are not part of the documented evidence for this antibody.