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CD81 Recombinant Monoclonal Mouse Antibody (2304.81) – Biotium Choice

CD81 (clone 2304.81) is a validated recombinant mouse monoclonal antibody that recognizes the human tetraspanin protein CD81. The antibody belongs to the Biotium Choice list of select antibodies that have been formulated and validated in-house for optimal performance.

Product Attributes

Antibody number




Biotium Choice Antibody


Antibody type

Biotium Choice Flow Antibodies, Primary


Recombinant Monoclonal

Host species





IgG1, kappa

Antibody reactivity (target)



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

Species reactivity

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

Human gene symbol


Entrez gene ID




Molecular weight

26 kDa

Antibody target cellular localization

Exosomes/EVs, Plasma membrane

Cell/tissue expression

Exosomes, Hepatocytes, Lymphocytes, Monocytes/macrophages

Verified antibody applications

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

Shelf life

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

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.

Antibody application notes

Immunofluorescence: 1 ug/mL, Western Blot: 0.1 ug/mL, Flow cytometry: 0.5-1 ug/million cells

Antibody research areas


Antibody/conjugate formulation

Conjugates: PBS/0.1% BSA/0.05% azide, Purified, BSA-free: 5 mg/mL in PBS without azide

Volume per assay

5 uL/test

Storage Conditions

Note: store unconjugated formats at -10 °C to -35 °C, Store conjugates at 2 °C to 8 °C

Regulatory status

For research use only (RUO)

Catalog #
25 tests
100 tests
1 mg
5 mg
Clear selection
(Please select quantity above )

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Product Description

CD81 (clone 2304.81) is a recombinant mouse monoclonal antibody that recognizes the human tetraspanin protein CD81. This antibody belongs to the Biotium Choice list of select antibodies that have been formulated and validated in-house for optimal performance. This antibody has been validated in flow cytometry and immunofluorescence microscopy. The antibody is available unlabeled or conjugated to CF® Dyes and Astral™ tandem dyes.

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.

ConjugationEx/EmConc.SizeCatalog No.Dye Features
CF®405M416/452 nm100 ug/mL25 tests (125 uL)P014-405M-125CF®405M Features
100 tests (500 uL)P014-405M-500
CF®488A490/516 nm100 ug/mL25 tests (125 uL)P014-488A-125CF®488A Features
100 tests (500 uL)P014-488A-500
CF® 568562/584 nm100 ug/mL25 tests (125 uL)P014-568-125CF®568 Features
100 tests (500 uL)P014-568-500
CF® 583R585/609 nm100 ug/mL25 tests (125 uL)P014-583R-125CF®583R Features
100 tests (500 uL)P014-583R-500
RPE-Astral™616496, 546, 566/617 nm100 ug/mL25 tests (125 uL)P014-R616-125
100 tests (500 uL)P014-R616-500
CF® 647Plus652/668 nm100 ug/mL25 tests (125 uL)P014-647P-125CF®647Plus Features
100 tests (500 uL)P014-647P-500
CF®700696/721 nm100 ug/mL25 tests (125 uL)P014-700-125CF®700 Features
100 tests (500 uL)P014-700-500
R-PE496, 546, 565/576 nm100 ug/mL25 tests (125 uL)P014-RPE-125
100 tests (500 uL)P014-RPE-500
APC651/660 nm100 ug/mL25 tests (125 uL)P014-APC-125
100 tests (500 uL)P014-APC-500
Purified (BSA-free)N/A5 mg/mL1 mgP014-1MG
5 mgP014-5MG

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