DESCRIPTION

Chitinase 3-like-1 (CHI3L1/YKL-40/CGP-39/GP-39) is a glycoprotein synthesized and secreted by a multitude of cells including macrophages, neutrophils, synoviocytes, chondrocytes, fibroblast-like cells, smooth muscle cells, and tumor cells. It plays a major role in tissue injury, inflammation, tissue repair, and remodeling responses. CHI3L1 has been strongly associated with diseases including asthma, arthritis, sepsis, diabetes, liver fibrosis, and coronary artery disease. CHI3L1 signaling plays a critical role in cancer cell growth, proliferation, invasion, metastasis, angiogenesis, activation of tumor-associated macrophages, and Th2 polarization of CD4+ T cells.

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	185.3	6.6	3.6
2	20	46.5	1.8	3.9
3	20	9.6	0.7	7.0

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	24	187.2	8.0	4.3
2	24	45.6	1.5	3.4
3	24	10.7	1.0	9.6

RECOVERY

The recovery of mouse CHI3L1/YKL40 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Mouse serum	1:800	98	84-111
	1:1,600	110	101-124
Cell culture supernatant	1:2	86	74-96
	1:4	91	80-102

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 mouse serum samples were initially diluted 1:100.)

		Mouse serum	Cell culture supernatant
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	103	101
	Range (%)	97-106	90-111
1:8	Average% of Expected	112	107
	Range (%)	105-120	99-113
1:16	Average% of Expected	112	111
	Range (%)	104-123	103-115

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Mouse CHI3L1/YKL40 Sandwich ELISA Kit produced at Sunlong Medical™.