Human CD81 antigen(CD81) ELISA kit

Product Details

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Customer Reviews and Q&A

Target Background

Product Details

Alternative Names

26 kDa cell surface protein TAPA 1 ELISA Kit; 26 kDa cell surface protein TAPA-1 ELISA Kit; 26 kDa cell surface protein TAPA1 ELISA Kit; CD 81 ELISA Kit; CD81 ELISA Kit; CD81 antigen (target of antiproliferative ELISA Kit 1) ELISA Kit; CD81 antigen ELISA Kit; CD81 molecule ELISA Kit; CD81_HUMAN ELISA Kit; CVID6 ELISA Kit; S5.7 ELISA Kit; TAPA 1 ELISA Kit; TAPA1 ELISA Kit; Target of the antiproliferative ELISA Kit 1 ELISA Kit; Tetraspanin 28 ELISA Kit; Tetraspanin-28 ELISA Kit; Tetraspanin28 ELISA Kit; Tspan 28 ELISA Kit; Tspan-28 ELISA Kit; Tspan28 ELISA Kit

Abbreviation

CD81

Uniprot No.

P60033

Species

Homo sapiens (Human)

Sample Types

serum, plasma, cell lysates, tissue homogenates

Detection Range

23.5 pg/mL-1500 pg/mL

Sensitivity

11.75 pg/mL

Assay Time

1-5h

Sample Loading Volume

50-100ul

Detection Wavelength

450 nm

Research Area

Immunology

Assay Principle

quantitative

Measurement

Sandwich

Precision

Linearity

To assess the linearity of the assay, samples were spiked with high concentrations of Human CD81 in various matrices and diluted with the Sample Diluent to produce samples with values within the dynamic range of the assay.

	Sample	Serum(n=4)
1:2	Average %	95
	Range %	88-101
1:4	Average %	102
	Range %	97-106
1:8	Average %	87
	Range %	80-94
1:16	Average %	93
	Range %	86-98

Recovery

Typical Data

These standard curves are provided for demonstration only. A standard curve should be generated for each set of samples assayed.

pg/ml

OD1

OD2

Average

Corrected

1500

2.425

2.534

2.480

2.319

750

1.535

1.617

1.576

1.416

375

0.923

0.938

0.930

0.770

187.5

0.489

0.509

0.499

0.339

0.332

0.321

0.326

0.166

0.250

0.253

0.251

0.091

23.5

0.212

0.204

0.208

0.047

0.163

0.158

0.160

ELISA Data Analysis

ELISA Standard Curve & Curve Expert software

Troubleshooting
and FAQs

ELISA kit FAQs

Storage

Store at 2-8°C. Please refer to protocol.

Shelf Life

6 months

Description

This ELISA kit provides quantitative measurement of CD81 (TAPA-1) in human serum, plasma, cell lysates, and tissue homogenates, supporting immunological research into this tetraspanin's roles in immune cell signaling and viral entry. Because CD81 is predominantly membrane-bound and shed at low levels into circulation, accurate quantification demands both high sensitivity and compatibility across soluble and cell-associated sample formats.

Detection Range: The 23.5–1500 pg/mL range accommodates the low picogram-level concentrations of soluble CD81 typically found in human plasma while also capturing elevated levels observed in hepatic inflammation and chronic HCV infection, minimizing the need for extensive sample concentration or dilution.

Sensitivity: At 11.75 pg/mL, the kit detects soluble CD81 in samples where shedding is minimal, such as healthy donor serum or conditioned media from unstimulated B cells, where circulating levels can fall below 50 pg/mL.

Sample Compatibility: Validation across plasma, serum, cell lysates, and tissue homogenates enables researchers to correlate circulating soluble CD81 with membrane-bound expression in lymphocytes or hepatic tissue within a single experimental framework.

Assay Efficiency: The 1–5 hour protocol requiring only 50–100 µL accommodates limited clinical specimens and primary cell lysates, supporting studies where patient biopsy material or sorted immune cell populations restrict available sample volume.

This kit is directly applicable to studies of hepatitis C virus entry mechanisms, B-cell co-receptor complex function, and exosome-mediated intercellular communication.

Related Products

Target Background

Function
(From Uniprot)

Structural component of specialized membrane microdomains known as tetraspanin-enriched microdomains (TERMs), which act as platforms for receptor clustering and signaling. Essential for trafficking and compartmentalization of CD19 receptor on the surface of activated B cells. Upon initial encounter with microbial pathogens, enables the assembly of CD19-CR2/CD21 and B cell receptor (BCR) complexes at signaling TERMs, lowering the threshold dose of antigen required to trigger B cell clonal expansion and antibody production. In T cells, facilitates the localization of CD247/CD3 zeta at antigen-induced synapses with B cells, providing for costimulation and polarization toward T helper type 2 phenotype. Present in MHC class II compartments, may also play a role in antigen presentation. Can act both as positive and negative regulator of homotypic or heterotypic cell-cell fusion processes. Positively regulates sperm-egg fusion and may be involved in acrosome reaction. In myoblasts, associates with CD9 and PTGFRN and inhibits myotube fusion during muscle regeneration. In macrophages, associates with CD9 and beta-1 and beta-2 integrins, and prevents macrophage fusion into multinucleated giant cells specialized in ingesting complement-opsonized large particles. Also prevents the fusion of mononuclear cell progenitors into osteoclasts in charge of bone resorption. May regulate the compartmentalization of enzymatic activities. In T cells, defines the subcellular localization of dNTPase SAMHD1 and permits its degradation by the proteasome, thereby controlling intracellular dNTP levels. Also involved in cell adhesion and motility. Positively regulates integrin-mediated adhesion of macrophages, particularly relevant for the inflammatory response in the lung.; (Microbial infection) Acts as a receptor for hepatitis C virus (HCV) in hepatocytes. Association with CLDN1 and the CLDN1-CD81 receptor complex is essential for HCV entry into host cell.; (Microbial infection) Involved in SAMHD1-dependent restriction of HIV-1 replication. May support early replication of both R5- and X4-tropic HIV-1 viruses in T cells, likely via proteasome-dependent degradation of SAMHD1.; (Microbial infection) Specifically required for Plasmodium falciparum infectivity of hepatocytes, controlling sporozoite entry into hepatocytes via the parasitophorous vacuole and subsequent parasite differentiation to exoerythrocytic forms.

Gene References into Functions

CD81 might be a potential prognostic biomarker associated with poor patient prognosis in breast cancer. PMID: 30117494
Tetraspanin hCD81 backbone domains are critical to signal for productive Hepatitis C Virus entry. A cholesterol-coordinating glutamate residue in CD81 promotes HCV infection. The backbone domains of hCD81 are additional HCV susceptibility-determining factors. PMID: 29677132
results demonstrate that the interaction of CD81 with SAMHD1 controls the metabolic rate of HIV-1 replication by tuning the availability of building blocks for reverse transcription, namely dNTPs.Together with its role in HIV-1 entry and budding into host cells, the data indicate that HIV-1 uses CD81 as a rheostat that controls different stages of the infection PMID: 28871089
CD81 is preferentially expressed in first trimester human placentas and progressively down-regulated with gestation advance in normal physiological conditions. CD81 up-regulation is detected in trophoblasts and cells in the villous core, and maternal sera of patients with early-onset severe preeclampsia. PMID: 28167787
CD81 cell surface expression had a negative impact on survival in acute myeloid leukemia. PMID: 27566555
Results from crystallography and molecular dynamics of CD81 long-extracellular loop (LEL) show that its flexibility is an inherent molecular property likely to be tuned by variation in pH and redox conditions. This tuning mechanism would explain the priming role ascribed to CD81LEL in rendering the virus-receptor complex fusogenic during cell entry. PMID: 27916518
Free energy calculations indicated that the E2/CD81 binding process might follow a two-step model involving (i) the electrostatic interaction-driven initial binding of human-specific E2-site2, followed by (ii) changes in the E2 orientation to facilitate the hydrophobic and van der Waals interaction-driven binding of E2-site1 PMID: 28481946
A new link between HCV receptor molecules and the hepatocyte glycocalyx, namely, CD81 and Synd-1. PMID: 27930836
Study used molecular dynamics simulations to gain insights into the role of local conformational flexibility in nanodomain formation in the plasma membrane, using the tetraspanin molecule CD81 as a model; suggest that exposing a flexible domain of CD81 enables binding to interaction partners by circumventing the restriction of orientation and conformational freedom of membrane proteins PMID: 27276264
Studies have shown that CD81 regulates cell migration and invasion, and has therefore been implicated in tumor growth, cancer progression and metastasis. CD81 is expressed in most types of cancer, and the overexpression or down-regulation of this molecule has been correlated with either good or bad prognosis. [review] PMID: 28408492
The transmembrane segments of CD81 pack as two largely separated pairs of helices, capped by the large extracellular loop (EC2) at the outer membrane leaflet. The two pairs of helices converge at the inner leaflet to create an intramembrane pocket with additional electron density corresponding to a bound cholesterol molecule within the cavity. PMID: 27881302
Results suggest that the CD81 antigen (CD81) expressed by B cells has differential effects on B cell proliferation or apoptosis according to Epstein-Barr virus (EBV) infection and the expression level of CD81. PMID: 26498453
CD81 expression was lower in systemic sclerosis patients compared to controls independent of disease duration. PMID: 26926492
IFI6 inhibits HCV entry by impairing EGFR mediated CD81/CLDN1 interactions. This may be relevant to other virus entry processes employing EGFR. PMID: 25757571
Data suggest that the intramolecular 188-196 bond restricts the intrinsic conformational dynamics of D-helix of cluster of differentiation 81 (CD81)-large extracellular loop (LEL), which is essential for hepatitis C virus entry. PMID: 26116703
LDLR was not required for the degradation of CD81 by PCSK9, but its presence strengthened the PCSK9 effect. PMID: 26195630
These data revealed the crucial role played by His490 and His621 in hepatitis C virus infection, particularly during CD81 binding in cell entry. PMID: 25701820
findings suggest that homozygous CD81 rs708564 TT may be a genetic modifier for avoiding HCV infection whether as a sole single nucleotide polymorphism or combined with the CLDN1 rs893051 GG genotype PMID: 25934191
Hsp70/40 stimulated the association of Hsp104 with aggregates and increased the duration of this association PMID: 25635054
Data indicate that HIV-1 colocalizes with CD81 antigen-lined vesicle compartments in astrocytes. PMID: 24587404
Vpu-mediated downregulation of CD81 from the surfaces of infected T cells contributed to preserving the infectiousness of viral particles. PMID: 25568205
The data suggest an important role played by the W(437)LAGLF(442) helix of the hepatitis C virus E2 protein in the hydrophobic interaction with the D-helix of CD81. PMID: 25339761
We have developed infectious pseudo particles of local 3a-isolate and concluded that a number of liver-specific surface proteins function along with CD81 and SRBI receptor regarding HCV infectivity PMID: 24549717
Amino acids Y507, V514, and V515 of hepatitis C virus E2 contribute to interaction with HCV receptor CD81. PMID: 24990994
CLEC4M and CD81 both are still crucial for hepatitis C virus entry into hepatocytes. PMID: 24965233
Authors show enhanced hepatoma migration and invasion following expression of CD81 and a reduction in invasive potential upon CD81 silencing. PMID: 24662676
These results strongly suggest that CD81 stimulates melanoma cell motility by inducing MT1-MMP expression through the Akt-dependent Sp1 activation signaling pathway, leading to increased melanoma invasion and metastasis. PMID: 24733393
study reported on seven CD81 SNP's present in human populations that all facilitate HCV entry in vitro PMID: 24211330
The large extracellular loop (LEL) of CD81 is a molecule that is highly conserved and it was hypothesised that variation in the CD81 LEL sequence may modify susceptibility to HCV infection; no differences in nucleotide sequence influencing susceptibility to, or outcome of hepatitis C virus infection or evidence of methylation of the gene were found. PMID: 24122777
Radiation increases the cellular uptake of exosomes through CD29/CD81 complex formation. PMID: 24667602
results demonstrate important roles of CD81 in both entry and budding stages of the influenza infection cycle. PMID: 24130495
A specific association between alpha4beta1 and CD81, CD82 and CD151 was demonstrated and antibodies to CD81 and CD82 augmented adhesion of proerythroblasts to Vascular Cell Adhesion Molecule-1. PMID: 23704882
Authors demonstrated that EWI-2wint promotes CD81 clustering and confinement in CD81-enriched areas. PMID: 23351194
Two SNPs in the CD81 gene, that encodes the molecule involved in the signal modulation of B lymphocytes, show a strong association with alloimmunization in sickle cell disease. PMID: 23762099
CD81 interacts with ICAM-1 and CD3 during conjugation between T cells and antigen-presenting cells PMID: 23858057
HRas signal transduction promotes hepatitis C virus cell entry by triggering the host CD81-CLDN1 complex formation. PMID: 23498955
Data indicate frequent down-regulation of CD81 expression in gastric cancer cell lines and primary tumor tissues. PMID: 23264205
In summary, these data highlight the dynamic nature of CD81 and demonstrate a role for CD81 lateral diffusion to regulate hepatitis C virus infection in a polarization-dependent manner. PMID: 23126643
Interaction of Rac1 with the C-terminal cytoplasmic domain of CD81 is a novel regulatory mechanism of the GTPase activity turnover. PMID: 23264468
These findings together indicate that the HCV RNA replication status plays a crucial determinant in HCV growth by modulating the expression and intracellular localization of CD81. PMID: 23349980
CD81 interacts with the T cell receptor to suppress signaling. PMID: 23226274
Fluorescent Resonance Energy Transfer studies confirm a role for these CD81 residues in claudin-1 association and Hepatitis C virus infection. PMID: 22897233
data demonstrate that EGFR internalization is critical for hepatitis C virus entry and identify a hitherto-unknown association between CD81 and EGFR PMID: 22855500
our results show that CD81 may have a relevant role in MM pathogenesis and represent a novel adverse prognostic marker in myeloma. PMID: 22333880
A novel membrane binding interface was revealed adjacent to the exposed HCV interaction site in the extracellular loop of CD81. PMID: 22740401
These results suggest that palmitoylation of CD81 should facilitate hepatitis C virus entry, at least in part, by regulating the association of CD81 with tetraspanin-enriched microdomains. PMID: 22560863
Soluble serum CD81 is elevated in patients with chronic hepatitis C and correlates with alanine aminotransferase serum activity. PMID: 22355327
Heptatitis c virus (HCV) specific E2 and host CD81 antibodies reduce HCV pseudoparticle entry. PMID: 22074322
Hepatitis C virus is primed by CD81 protein for low pH-dependent fusion PMID: 21737455
CD81 is required for the formation of actin membrane protrusions via RAC1 activation in adhesion-dependent immune cell migration. PMID: 21677313

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Involvement in disease

Immunodeficiency, common variable, 6 (CVID6)

Subcellular Location

Cell membrane; Multi-pass membrane protein. Basolateral cell membrane; Multi-pass membrane protein.

Protein Families

Tetraspanin (TM4SF) family

Tissue Specificity

Expressed on B cells (at protein level). Expressed in hepatocytes (at protein level). Expressed in monocytes/macrophages (at protein level). Expressed on both naive and memory CD4-positive T cells (at protein level).

Database Links

HGNC: 1701

OMIM: 186845

KEGG: hsa:975

STRING: 9606.ENSP00000263645

UniGene: Hs.54457

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Code	CSB-EL004960HU-IS
Size	96T,5×96T,10×96T
Price	Request a Quote
Trial Size	24T ELISA Kit Trial Size (Only USD$150/ kit) * Sample kit cost can be deducted as a $30 credit for each 96-assay kit of the same analyte and brand you subsequently purchase within six months until depleted. More details >> Interested in a trial size? Please leave a message below.
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Intra-assay Precision (Precision within an assay): CV%<8%

Three samples of known concentration were tested twenty times on one plate to assess.

Inter-assay Precision (Precision between assays): CV%<10%

Three samples of known concentration were tested in twenty assays to assess.