Microparticle-enhanced nephelometric immunoassay of lysozyme in milk and other human body fluids.
Quantitation of lysozyme in human milk was performed by a microparticle-enhanced nephelometric immunoassay based on the measurement of the light scattered during the competitive immunoagglutination of a microparticle-lysozyme conjugate with an anti-lysozyme antiserum. This immunoassay has a detection limit of 8 microg/L of reaction mixture and can be performed using diluted milk (1:6000, in reaction mixture), excluding sample pretreatment. Human milk lysozyme can be quantified over the concentration range 0.09-1.50 g/L, with within- and between-run coefficients of variation <5%. Changes in the lysozyme concentration of human milk during lactation were determined in 636 samples. Lysozyme concentrations (mean +/- SE) decreased from colostrum (0.36 +/- 0.02 g/L) to transitional milk (0.30 +/- 0.01 g/L) and mature milk during days 15-42 (0.30 +/- 0.01 g/L), then increased in the mature milk during days 43-56 (0.35 +/- 0.01 g/L) and especially during days 57-84 (0.83 +/- 0.05 g/L). The proportion of lysozyme contributing to total protein was found to rise during lactation and was as follows: colostrum (1.7%), transitional milk (2.3%), and mature milk from days 15-28 (2.7%), days 29-42 (3.1%), days 43-56 (3.8%), and days 57-84 (7.3%). The assay developed for milk was also suitable for the determination of lysozyme in other human body fluids.
GRIP, Immunology Laboratory, Faculty of Medicine, Vandoeuvre les Nancy, France. paulmont@grip.u-nancy.fr
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Montagne
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Cuillière
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Molé
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Béné
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Faure
D000293:Adolescent; D000328:Adult; D001826:Body Fluids / Q000737:chemistry* / Q000201:enzymology; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007774:Lactation / Q000378:metabolism; D008863:Microspheres; D008875:Middle Aged; D008895:Milk, Human / Q000737:chemistry* / Q000201:enzymology; D009113:Muramidase / Q000032:analysis* / Q000097:blood / Q000652:urine; D009391:Nephelometry and Turbidimetry; D012463:Saliva / Q000737:chemistry / Q000201:enzymology; D013997:Time Factors
D009113:Muramidase