DESCRIPTION

CD33 is a type I transmembrane receptor glycoprotein that functions as an immune inhibitory receptor. It is expressed on myeloid cells, including monocytes, macrophages, and microglia, and plays a role in immune regulation and cell adhesion. CD33 is involved in the suppression of immune responses, particularly in the context of Alzheimer's disease, where it inhibits microglial uptake of amyloid beta. Additionally, CD33 is implicated in the regulation of inflammation and immune cell activation.

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	4.86	0.18	3.70
2	8	1.03	0.08	7.77
3	8	0.51	0.02	3.92

Inter-assay Precision

Sample	n	Mean (pg/mL)	SD	CV%
1	16	4.78	0.16	3.35
2	16	1.03	0.09	8.74
3	16	0.51	0.02	3.92

RECOVERY

The recovery of human CD33 spiked to three different levels throughout the range of the assay in various matrices was evaluated.

Sample Type		Average% of Expected	Range (%)
Human plasma	1:8	119	113-122
	1:16	120	114-127
Cell lysate	1:64	92	91-94
	1:128	97	94-98

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 1:8.)

		Human plasma(Sample diluent PT 4B1)	Cell lysate(Sample diluent PT 3-ef)
1:2	Average% of Expected	100	100
	Range (%)	-	-
1:4	Average% of Expected	117	112
	Range (%)	116-118	107-116
1:8	Average% of Expected	129	108
	Range (%)	126-132	103-113
1:16	Average% of Expected	112	84
	Range (%)	108-117	79-90

CALIBRATION

This immunoassay is calibrated against a highly purified recombinant human CD33 produced at Sunlong Medical™.