DESCRIPTION

CD23, also known as low affinity immunoglobulin epsilon Fc receptor, is a transmembrane glycoprotein present on a subpopulation of B lymphocytes in germinal centres, EBV-transformed B-lymphoblastoid cell lines, follicular dendritic cells, and a subpopulation of peripheral blood cells. CD23 has essential roles in the regulation of IgE production and in the differentiation of B-cells. CD23 can be cleaved into soluble fragment (soluble CD23, sCD23) of various sizes displaying pleiotropic biological activities. Increased plasma levels of sCD23 have been reported in allergic disorders, acute viral diseases, lepromatous leprosy, B-CLL, and inflammatory diseases like RA, SLE and sarcoidosis.

PRINCIPLE OF THE ASSAY

An anti-tag antibody is pre-coated onto the bottom of wells. After adding antigen or samples, Tagged-Capture antibody and HRP-conjugated detection antibody, a sandwich complex is formed in the solution. TMB acts as a HRP substrate, and the solution color will change from colorless to blue. A stop solution containing sulfuric acid turns the 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	2,326.4	72.7	3.1
2	8	590.9	17.8	3.0
3	8	289.7	9.9	3.4

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	16	2,294.7	80.5	3.5
2	16	568.8	26.8	4.7
3	16	282.2	12.4	4.4

RECOVERY

The recovery of human CD23 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Human plasma	1:4	82	81-83
	1:8	89	86-92
Cell culture supernatant	1:8	106	101-112
	1:16	98	94-100

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.

		Human plasma	Cell culture supernatant
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	111	102
	Range (%)	107-115	101-102
1:8	Average% of Expected	107	113
	Range (%)	100-114	109-116
1:16	Average% of Expected	98	110
	Range (%)	92-105	108-113

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human CD23 produced at Sunlong Medical™.