DESCRIPTION

CXCL10 ( also known as IP-10) is a member of the CXC chemokine family which binds to the CXCR3 receptor to exert its biological effects. CXCL10 is a 12-kDa protein and constitutes two internal disulfide cross bridges. The predicted signal peptidase cleavage generates a 10-kDa secreted polypeptide with four conserved cysteine residues in the N-terminal. The CXCL10 gene localizes on chromosome 4 at band q21, a locus associated with an acute monocytic/B-lymphocyte lineage leukemia exhibiting translocation of t (4; 11) (q21; q23). CXCL10 mediates leukocyte trafficking, adaptive immunity, inflammation, haematopoiesis and angiogenesis. Under proinflammatory conditions CXCL10 is secreted from a variety of cells, such as leukocytes, activated neutrophils, eosinophils, monocytes, epithelial cells, endothelial cells, stromal cells (fibroblasts) and keratinocytes in response to IFN-γ.

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 8 times on one plate to assess intra-assay precision. Inter-assay Precision (Precision between assays) Three samples of known concentration were tested in 16 separate assays to assess inter-assay precision.

Intra-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	8	583.5	28.9	5.0
2	8	144.1	5.5	3.8
3	8	43.1	1.1	2.6

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	16	553.1	43.7	7.9
2	16	141.9	6.1	4.3
3	16	42.1	2.1	5.1

RECOVERY

The recovery of human CXCL10/IP-10 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Human plasma	1:2	92	83-103
	1:4	95	91-99
Saliva	1:4	95	94-95
	1:8	102	89-112

LINEARITY

To assess the linearity of the assay, human plasma and saliva samples were diluted with the appropriate Sample Diluent to produce samples with values within the dynamic range of the assay.

		Human plasma (Sample DiluentPT 4-oc)	Saliva (Sample Diluent PT 4)
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	111	96
	Range (%)	106-116	92-120
1:8	Average% of Expected	104	116
	Range (%)	101-106	107-126
1:16	Average% of Expected	-	125
	Range (%)	-	124-126

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Human CXCL10/IP-10 Sandwich ELISA Kit produced at Sunlong Medical™.