CD81 ELISA Kit (Cluster Of Differentiation 81)

Full Name: CD81 ELISA Kit (Cluster Of Differentiation 81)
Reactivity: Human
Sample Type: Serum, Tissue Homogenates, Biological Fluids, Plasma
Sensitivity: 0.188 ng/ml


Cluster of Differentiation 81 (CD81) is a cell surface protein that is 26kDa and it is encoded by the CD81-gene. The gene is found to be located on chromosome 11 (short arm). It is a 236 amino acids protein, that is not post translationally modified. It contains four transmembrane domains, however, both the carboxyl and amino terminals are present within the intracellular side of the membrane. The human protein has 60% amino acid sequence identity with murine. It is expressed in cells including; keratinocytes, epithelial, endothelial, platelets, erythrocytes, mast cells, chondrocytes and neural cells. The gene encoding contains 14 exons and spans 18 kilobases of DNA.

CD81 is composed of three isoforms: CD81a-c. The primary structure and the function of these isoforms are not known with certainty. It has a wide range of tissue distribution and is highly expressed in the brain, more specifically the cortex. It is associated with reduced severity of Alzheimer’s disease, protection against inflammation and atherosclerosis. The expression also correlates with the expression of synaptophysin and neurofilament, which are markers for neurons and glial cells, respectively. The gene is ubiquitously expressed in the human body. The protein encoded by this gene contains four tandem repeats of a 7-amino acid sequence with an Ig-like domain involved in signal transduction. It is a member of the integrin alpha subfamily of cell adhesion molecules. It functions as a receptor for fibronectin, integrins and vitronectin.


Human CD81 ELISA kit can be used to detect levels of cluster of differentiation 81 antigen (CD81, TAPA 1, Tspan 28, tetraspanin 28) present is human plasma, serum, biological fluids and tissue homogenates.


All reagents supplied need to be stored at 2 °C – 8 °C, unopened reagents will retain reactivity until expiration date. Do not use reagents beyond this date.

  • One 96-Well Plate: Pre-coated with anti-CD81 antibody.
  • Standards: Lyophilized recombinant.
  • Sample/Standard Dilution Buffer.
  • Biotinylated-labelled Antibody.
  • Antibody Dilution Buffer.
  • HRP-Streptavidin Conjugate (SABC).
  • SABC Dilution Buffer.
  • TMB Substrate.
  • Wash Buffer (25x).
  • Plate Sealer.
  • Product Instructions.


For this CD81 ELISA kit it is recommended that a standard curve is generated for each assay carried out.

Standard Curve: 0, 0.312, 0.625, 1.25, 2.5, 5, 10, 20 pg/ml.
Reactivity: Human
Sensitivity: 0.188 ng/ml
Range: 0.313 – 20 ng/ml
Principle: Sandwich
Application: Research Use Only.


– Specificity: Highly specific for CD81, no cross reactivity or interference between CD81 and analogues was detected.
– Recovery: Serum (87 – 101%), EDTA Plasma (88 – 101%), Heparin Plasma (87 – 98%).
– Linearity: Serum (91 – 102%), EDTA Plasma (87 – 105%), Heparin Plasma (87 – 105%).
– Precison Intra-Assay: CV < 8%.
– Precison Inter-Assay: CV < 10%.
– Stability: Less than 10%.


  1. CD81 marks immature and dedifferentiated pancreatic β-cells. Mol Metab. (2021) 49: 101188. Salinno C., et al.
  2. Tetraspanin CD81 regulates HSV-1 infection. Med Microbiol Immunol. (2020) 209 (4): 489-498. Benayas B., et al.
  3. CD81 (TAPA-1): a molecule involved in signal transduction and cell adhesion in the immune system. Annu Rev Immunol. (1998) 16: 89-109. Levy S., et al.
  4. Anti-CD81 antibody blocks vertical transmission of avian leukosis virus subgroup J. Vet Microbiol. (2022) 264: 109293. Liao L., et al.


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