An enzyme-linked immunosorbent assay for plasma-lactoferrin. Concentrations in 362 healthy, adult blood donors

Abstract

Very different concentrations of plasma-lactoferrin in healthy adults have been reported in the literature. We compared three commercially available lactofer-rins and lactoferrin purified in our laboratory as calibrators in an ELISA. No statistical differences among these preparations of lactoferrin were detected. The concentration of purified lactoferrin was measured by dry weight, and efforts were made in order to minimize loss of purified lactoferrin by adhesion to tubes etc. and thus, secure accuracy of the method. Dilutions were made in PBS 0.01 moll^-1 with NaCl 0.436moll^-1, (NH₄)₂SO₄ 0.5moll^-1, BSA 5gl^-1 and normal rabbit IgG 10mgl^-1, which was shown to give parallel dilution curves of primary calibrator, secondary calibrator and plasma samples.

No significant difference in the content of lactoferrin in neutrophils (median; range) among men (1.78; 0.83-4.48 μg 10^-6 neutrophils; n = 20) and women (2.12; 1.16-9.30 μg 10^-6 neutrophils; n = 14) was found.

Lactoferrin was analysed in EDTA-plasma obtained from 135 female and 227 male blood donors. Median concentrations were 84.7 and 97.8 μg1^-1 respectively, while 2.5% and 97.5% reference limits (with 90% confidence intervals) were estimated to 42.9 (38.7-47.4) μg1^-1 and 166.9 (151.0-186.3) μg 1^-1 for women and 52.3 (49.1-55.6) μg 1^-1 and 189.9 (175.9-206.4) μg 1^-1 for men, respectively.

Key Words:

• accuracy
• calibrator
• Elisa
• neutrophil granulocytes
• reference limits