DESCRIPTION

Chemokine (C-X-C motif) ligand 13 (CXCL13), also known as B lymphocyte chemoattractant (BLC) or B cell-attracting chemokine 1 (BCA1), is a protein ligand. CXCL13 is chemotactic for B cells belonging to both the B-1 and B-2 subsets, and effects by interacting with chemokine receptor CXCR5. CCL19, CCL21 and CXCL13 expression are related to local immune responses to influenza virus infection in mice lung. CXCL13 also acts as inducers in early innate immunity and formation of protective lymphoid follicles within granulomas. CXCL13 expression has correlation with the pathogenesis of aberrant lymphoid structures, and acts as unfavorable prognosis in multiple sclerosis, Sjögren's, myasthenia gravis, and SLE.

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	540.7	19.1	3.5
2	20	130.7	4.3	3.3
3	20	26.7	1.4	5.1

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	24	502.6	19.6	3.9
2	24	124.8	6.3	5.1
3	24	27.0	1.8	6.6

RECOVERY

The recovery of mouse CXCL13/BCA1 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Mouse serum	1:4	82	70-108
	1:8	82	69-96
Cell culture supernatant	1:4	112	108-116
	1:8	104	99-108

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.

		Mouse serum	Cell culture supernatant
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	117	88
	Range (%)	113-122	87-90
1:8	Average% of Expected	123	84
	Range (%)	118-127	83-87
1:16	Average% of Expected	-	81
	Range (%)	-	77-89

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human Mouse CXCL13/BCA1 Sandwich ELISA Kit produced at Sunlong Medical™.