DESCRIPTION

CD137, also known as TNFRSF9 or 4-1BB, is an inducible T cell surface receptor which belongs to the tumor necrosis factor receptor superfamily. CD137 is a transmembrane protein expressed on the surface of activated T-cells. In addition, activationdependent expression of CD137 has also been found in B lymphocytes, monocytes, and diverse nonlymphoid cell types. CD137 provides a co-stimulatory signal that enhances the survival, and differentiation of cells, and has a crucial role in the development of CD8 cytotoxic T cells and anti-tumor immunity. Soluble forms of CD137 (sCD137) are generated by differential splicing and are released by activated lymphocytes. Elevated serum sCD137 level has been associated with some diseases, including rheumatoid arthritis, multiple sclerosis, chronic lymphocytic leukemia, and acute coronary syndrome.

PRINCIPLE OF THE ASSAY

Sandwich ELISA structure (Detection antibody labeled with HRP) A capture antibody is pre-coated onto the bottom of wells which binds to analyte of interest. A detection antibody labeled with HRP also binds to the analyte. TMB acts as the HRP substrate and the solution color will change from colorless to blue. A stop solution containing sulfuric acid turns solution yellow. The color intensity is proportional to the quantity of bound protein which is measurable at 450 nm with the correction wavelength set at 630 nm.

PRECISION

Intra-assay Precision (Precision within an assay) Three samples of known concentration were tested 20 times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in 24 separate assays to assess inter-assay precision.

Intra-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	20	225.5	4.0	1.8
2	20	54.9	0.9	1.6
3	20	12.6	0.4	3.3

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	24	220.0	4.7	2.1
2	24	53.8	1.3	2.4
3	24	13.5	0.6	4.2

RECOVERY

The recovery of human TNFRSF9/CD137 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Human serum	1:4	94	90-99
	1:8	93	90-97
Cell culture supernatant	1:16	103	98-107

LINEARITY

To assess the linearity of the assay, samples were diluted with the appropriate Sample Diluent to produce samples with values within the dynamic range of the assay. (The cell culture supernatant was initially diluted 1:2.)

		Human serum(Sample Diluent PT 1)	Cell culture supernatant(Sample Diluent PT 3-ec)
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	112	98
	Range (%)	107-118	96-101
1:8	Average% of Expected	102	97
	Range (%)	93-111	96-99
1:16	Average% of Expected	107	100
	Range (%)	90-124	98-101

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Human TNFRSF9/CD137 Sandwich ELISA Kit produced at Sunlong Medical™.

Ordering & shipping

• Minimum order: 1 kit
• Lead time: varies with order quantity and specifications. Please consult your local distributor or our sales team for confirmation
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• Shipping: FedEx / DHL / UPS express; cold-chain packing available on request
• Price: USD, per kit (48T / 96T options available)