NDT Advance Access originally published online on April 12, 2006
Nephrology Dialysis Transplantation 2006 21(6):1729-1730; doi:10.1093/ndt/gfl129
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Mannose-binding lectin level and polymorphism in patients on long-term peritoneal dialysis—level of serum mannose binding lectin with end-stage renal disease
Email: atsushis{at}med.nihon-u.ac.jpSir,
In their interesting article, Lam et al. [1] reported that dialysis patients had a significantly lower serum level of mannose binding lectin (MBL) than healthy individuals. This differs from our results [2] in that the mean level of serum MBL was significantly higher in pre-haemodialysis and haemodialysis patients than in healthy controls. The difference in results might be caused by the major difference in the technical measuring method. Lam et al. [1] measured serum MBL level by capturing with mannan. In contrast, we measured serum MBL concentration by enzyme-linked immunosorbent assay developed by Terai et al. [3], with minor modifications. Briefly, microtitre plates were coated with polyclonal anti-MBL rabbit IgG in carbonate buffer (pH 9.6), and serum samples were diluted 1:100 with phosphate-buffered saline and loaded into the wells. Next, plates were incubated with a second-step mAb against MBL (3E7) and a third-step with biotinylated goat antimouse IgG. Finally, avidin–biotin complex was added to each well. The colour was developed with 2-2'azino-di-(3-ethylbenzthiazoline sulfonic acid) in 0.1 mol/l of citrate buffer containing 0.03% H2O2. Absorbance was read at 405 nm in a microplate reader. The calculation of the amount of MBL in samples was based on a standard curve obtained using purified human MBL. This method is designed to measure whole MBL concentration in serum. On the other hand, Lam et al. [1] measured serum MBL concentration only by its binding in microtitre wells coated with mannan, in short, a functional MBL. Since three subunits (32 kDa) form a triple helix (the base structural unit) at the collagen-like domain within the MBL molecule, it was estimated that these trimeric structural units associated again by disulfide bridges and formed from trimers to hexamers. The large and middle oligomers were almost equal in their ability to activate complement, whereas the small oligomers had very low or no activity [4].
C-reactive protein (CRP) is synthesized primarily in the liver, and pro-inflammatory cytokines such as interleukin-6, interleukin-1, and tumour necrosis factor-
, whose levels are upregulated in chronic renal failure [5], modulate the serum level of CRP during the acute phase response. As MBL-like CRP is a positive acute-phase protein, the elevated serum MBL level in haemodialysis patients in theory may not represent a discrepancy. Since patients on haemodialysis suffer from various inflammatory states, an elevated MBL level may be an appropriate response in these patients.
Recently, we reported on MBL and mortality in haemodialysis patients [6]. In the article, the non-survivors had a significantly higher high-sensitivity-CRP (hs-CRP), and a lower serum MBL level than the survivors. Multivariate analysis of factors predicting all-cause mortality followed by multivariate logistic regression analysis identified serum MBL level <5 µg/ml and hs-CRP level (every 10 µg/dl increase) as variables that independently predicted all-cause mortality.
Although the genotypes of the MBL gene of the patients in our study were not determined, we submit that serum MBL represents an innovative clinical marker, and stress the importance of its measurement by our method.
Conflict of interest statement. None declared.
Division of Nephrology and Endocrinology Department of Medicine Nihon University School of Medicine Itabashi Tokyo Japan
References
- Lam MF, Leung JC, Tang CC et al. Mannose binding lectin level and polymorphism in patients on long-term peritoneal dialysis. Nephrol Dial Transplant 2005; 20: 2489–2496
[Abstract/Free Full Text] - Satomura A, Endo M, Ohi H et al. Significant elevations in serum mannose-binding lectin levels in patients with chronic renal failure. Nephron 2002; 92: 702–704[CrossRef][Web of Science][Medline]
- Terai I, Kobayashi K, Fujita T, Hagiwara K. Human serum mannose binding protein (MBP): development of an enzyme-linked immunosorbent assay (ELISA) and determination of levels in serum from 1085 normal Japanese and in some body fluids. Biochem Med Metab Biol 1993; 50: 111–119[CrossRef][Web of Science][Medline]
- Yokota Y, Arai T, Kawasaki T. Oligomeric structures required for complement activation of serum mannan-binding proteins. J Biochem 1995; 117: 414–419
[Abstract/Free Full Text] - Kimmel PL, Phillips TM, Simmens SJ. et al. Immunologic function and survival in hemodialysis patients. Kidney Int 1998; 54: 236–244[CrossRef][Web of Science][Medline]
- Satomura A, Endo M, Ohi H et al. Serum mannose-binding lectin levels in maintenance hemodialysis patients: impact on all-cause mortality. Nephron Clin Pract 2006; 102: c93–c99[Medline]
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