Abstract
A sandwich enzyme immunoassay method for measuring a platelet-specific protein, platelet factor 4 (PF4) was developed by mean of purified antibodies to PF4. The assay system consisted of polystyrene balls with immobilized antibody F(ab′)2 fragments and the same antibody Fab′ fragments labeled with β-D-galactosidase from E. coli. The measurable range was from 30pg to 3ng of PF4 per each tube. The results obtained with the enzyme immunoassay correlated well with those of a radioimmunoassay (γ=0.952, y=0.954x+2.43; n=36). The plasma PF4 levels in healthy subjects were 6.4±1.4ng/ml (±1 SD).
The levels of PF4 in platelet rich plasma obtained by platelet apheresis were 14.7±1.5μg/109 cells. Platelets contained large amounts of PF4, while, the levels of PF4 in red blood cells and lymphocytes were very low, confirming the previous findings that PF4 is localized mainly in blood platelets. The levels of PF4 in plasma of platelet concentrates processed 24hr before and stored at 22°C were high (3.22±1.43μg/ml).
