DESCRIPTION

CD38, also known as ADP-ribosyl cyclase 1, is a type II transmembrane glycoprotein with a short N-terminal cytoplasmic tail, a single membrane-spanning domain, and a C-terminal extracellular region with four N-glycosylation sites. The extracellular domain of CD38 has bifunctional enzyme activities that catalyze synthesis of cyclic ADP ribose from nicotinamide adenine dinucleotide (NAD) and hydrolysis of cyclic ADP ribose to adenosine diphosphoribose. CD38 is expressed on a variety of hematopoietic and non-hematopoietic cells and is involved in diverse processes such as generation of calcium-mobilizing metabolites, cell activation, and chemotaxis. In addition to the membrane form, CD38 can also exist as a soluble form (sCD38), which is derived from the membrane form by proteolytic cleavage occurring near the cell membrane.

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	1,012.8	26.4	2.6
2	8	260.7	3.3	1.3
3	8	129.0	2.8	2.2

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	16	1,067.1	64.4	6.0
2	16	264.3	6.7	2.5
3	16	132.9	4.8	3.6

RECOVERY

The recovery of human CD38 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	86	76-100
	1:4	88	84-91
Cell lysate	1:320	91	88-98
	1:640	96	89-104

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 cell lysate was initially diluted 1:40.)

		Human plasma (SampleDiluent PT 3)	Cell lysate (Sample Diluent PT 4B1)
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	103	102
	Range (%)	100-106	95-109
1:8	Average% of Expected	96	112
	Range (%)	91-100	100-125
1:16	Average% of Expected	87	109
	Range (%)	79-96	103-115

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human CD38 produced at Sunlong Medical™.