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CD81 Monoclonal Mouse Antibody (5A6) – Biotium Choice

CD81 (clone 5A6) is a validated mouse monoclonal antibody that recognizes the human tetraspanin protein CD81. The antibody belongs to the Biotium Choice list of select antibodies that have been validated and optimized in-house for optimal performance.

Product Attributes

Antibody number


Storage Conditions

Store at 2 to 8 °C

Shelf life

Guaranteed for at least 24 months from date of receipt when stored as recommended

Antibody/conjugate formulation

Purified: 0.5 mg/mL in PBS/0.05% azide, Conjugates: PBS/0.1% BSA/0.05% azide

Antibody research areas


Antibody application notes

Flow Cytometry: 0.5-1 ug/mL (or, 0.05-0.1 ug/million cells), Immunofluorescence: 1 ug/mL, Western Blot: 0.1 ug/mL

Positive control

Ramos, Daudi, Raji, U266, HUT-78, HUT-102, Jurkat, HL-60, KG1a, A293, A431, MG63, MCF-7, and human lymphocytes. Tonsil or liver tissue.

Verified antibody applications

Flow (surface) (verified), IF (verified), WB (verified)

Cell/tissue expression

Exosomes, Hepatocytes, Lymphocytes, Monocytes/macrophages

Antibody target cellular localization

Exosomes/EVs, Plasma membrane

Molecular weight

26 kDa





Entrez gene ID


Human gene symbol


Species reactivity

Baboon, Cynomolgus monkey, Human, Mouse (low reactivity), Non-human primates


CD81; Target of the antiproliferative antibody 1 (TAPA-1); Tetraspanin-28; Tspan-28

Antibody reactivity (target)



IgG1, kappa



Host species




Biotium Choice Antibody


Volume per assay

5 uL/test

Antibody type

Biotium Choice Flow Antibodies, Primary

Regulatory status

For research use only (RUO)

Catalog #
25 tests
100 tests
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Product Description

CD81 (clone 5A6) is a mouse monoclonal antibody that recognizes the human tetraspanin protein CD81. This antibody belongs to the Biotium Choice list of select antibodies that have been validated and optimized in-house for optimal performance. This antibody has been validated in flow cytometry, in immunofluorescence microscopy, and in western blot. The antibody is available conjugated to R-Phycoerythrin (R-PE or PE) or RPE-Astral™616. It is supplied in PBS, 0.1% BSA, 0.05% azide.

CD81 has a very broad cellular distribution, being expressed on T- and B-lymphocytes, NK cells, thymocytes, eosinophils, fibroblasts, epithelial and endothelial cells. Neutrophils, erythrocytes and platelets are negative, while monocytes are variably positive. CD81 is a member of a family of tetraspanin transmembrane proteins, including CD9, CD37, CD53, CD63, and CD82. It associates with CD19, CD21, Leu 13, and integrins on cell membrane and is involved in signal transduction in B lymphocyte development and cell adhesion. CD81 also acts as a receptor for the envelope protein E2 of chronic hepatitis C virus. Antibodies to CD81 have anti-proliferative effects on different lymphoid cell lines, particularly those derived from large cell lymphomas.

Tetraspanin proteins CD9, CD63, and CD81, are the most common proteins used as exosome markers. Tetraspanins are plasma membrane proteins with many proposed functions, including activation and sorting of other membrane proteins. They are also thought to play a role in the targeting of proteins to multivesicular bodies (MVBs) and exosomes. These tetraspanins are broadly expressed on many cell types and can therefore be detected on many types of exosomes, but their expression levels vary depending on the cell type of origin.

As an isotype control, we recommend Isotype Control, Monoclonal Mouse IgG1 Kappa (IGG1/1331) for this antibody. View our full catalog of Biotium Choice antibodies, optimized and validated for the best results in flow cytometry.

Exosome Stains and Antibodies

Biotium also offers ExoBrite™ CD81 Flow Antibody and ExoBrite™ CD81 Western Antibody that are validated for optimal detection of isolated exosomes by flow cytometry or western blotting. Learn more about our products for exosome research.

CD81 Monoclonal Mouse Antibody (5A6) - Biotium Choice

ConjugationEx/EmConc.SizeCatalog No.Availability
CF®405M416/452 nm100 ug/mL25 tests (125 uL)P005S-405M-125Discontinued, see replacement P014-405M
100 tests (500 uL)P005S-405M-500
CF®488A490/516 nm100 ug/mL25 tests (125 uL)P005S-488A-125Discontinued, see replacement P014-488A
100 tests (500 uL)P005S-488A-500
CF®568562/584 nm100 ug/mL25 tests (125 uL)P005S-568-125Discontinued, see replacement P014-568
100 tests (500 uL)P005S-568-500
RPE-Astral™616496, 546, 566/617 nm100 ug/mL25 tests (125 uL)P005S-R616-125Available
100 tests (500 uL)P005S-R616-500
CF®700696/721 nm100 ug/mL25 tests (125 uL)P005S-700-125Discontinued, see replacement P014-700
100 tests (500 uL)P005S-700-500
R-PE496, 546, 565/576 nm100 ug/mL25 tests (125 uL)P005S-RPE-125Available
100 tests (500 uL)P005S-RPE-500
Purified (BSA-free, 0.5 mg/mL)N/A0.5 mg/mL200 uL (100 ug)P005-200uLDiscontinued, see replacement P014

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