DESCRIPTION

CXC chemokine ligand 16 (CXCL16) is a CXC soluble chemokine, an adhesion molecule and a cell surface scavenger receptor. CXCL16 regulates inflammation, tissue injury and fibrosis. CXCL16 exists as a transmembrane form (TM-CXCL16) as well as a soluble form (sCXCL16) that is cleaved by proteolytic enzymes. CXCL16 is produced by several inflammatory cells including macrophages, dendritic cells, smooth muscle cells or lymphocytes. CXCL16 is expressed in various cancers, including pancreatic, prostate, breast, colorectal, and nonsmall cell lung cancer. CXCL16) has been proposed as an important pathogenic mediator in inflammatory diseases, such as rheumatoid arthritis, hepatitis or atherosclerosis.

PRINCIPLE OF THE ASSAY

Sandwich ELISA structure (Detection antibody labeled with biotin) A capture antibody is pre-coated onto the bottom of wells which binds to analyte of interest. A detection antibody labeled with biotin also binds to the analyte. Streptavidin-HRP binds to the biotin. 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	241.1	10.8	4.5
2	20	56.1	1.7	3.0
3	20	12.7	0.5	3.9

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	24	260.7	17.1	6.6
2	24	56.0	3.2	5.8
3	24	12.7	0.7	5.8

RECOVERY

The recovery of human CXCL16 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average % of Expected	Range (%)
Human plasma	1:32	100	83-119
	1:64	98	88-110
Human serum	1:32	98	89-103
	1:64	84	76-96
Cell culture supernatant	1:2	88	82-118
	1:4	85	83-98

LINEARITY

To assess the linearity of the assay, three samples were spiked with high concentrations of human CXCL16 in various matrices and diluted with the appropriate Sample Diluent to produce samples with values within the dynamic range of the assay. (The plasma and serum samples were initially diluted 1:4)

		Human plasma	Human serum	Cell culture supernatant
No diluted	Average% of Expected	-	-	95
	Range (%)	-	-	82-117
1:2	Average% of Expected	93	91	95
	Range (%)	80-118	80-101	93-100
1:4	Average% of Expected	92	100	97
	Range (%)	86-100	100-101	89-103
1:8	Average% of Expected	96	111	107
	Range (%)	88-100	108-115	100-116
1:16	Average% of Expected	103	118	-
	Range (%)	88-105	115-119	-

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human CXCL16 produced at Sunlong Medical™.