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Heterogeneity of MBL-MASP complexes
Karine R Mayilyan1, Julia S Presanis, James N Arnold
1MRC Immunochemistry Unit, Department of Biochemistry, Oxford University, South Parks Roads, Oxford OX1 3QU, UK.
Molecular Immunology
|August 17, 2005
Summary
Human mannose-binding lectin (MBL) complexes with MASP-1 and MASP-2 proteases show variable composition. Their concentrations vary significantly between individuals, suggesting distinct MBL-MASP-1 and MBL-MASP-2 complex populations.
Area of Science:
- Immunology
- Biochemistry
- Human genetics
Background:
- Mannose-binding lectin (MBL) is a key component of the innate immune system.
- MBL circulates in serum associated with MBL-associated serine proteases (MASPs), primarily MASP-1 and MASP-2.
- The precise stoichiometry and composition of MBL-MASP complexes in healthy individuals are not fully understood.
Purpose of the Study:
- To investigate the stoichiometry and composition of human MBL-MASP complexes in a population.
- To determine the inter-individual variation in MBL-MASP complex composition.
Main Methods:
- Sera from 152 healthy individuals were used.
- MBL-MASP complexes were captured using mannan-coated microtitre plates.
- Bound MBL was quantified by ELISA.
- Enzymatic activities of MASP-1 and MASP-2 were measured using amidolytic and C4 fixation assays.
Main Results:
- MASP-1 and MASP-2 activities showed positive correlations with MBL concentration.
- When normalized to MBL concentration, MASP-1 activity was inversely correlated with MASP-2 activity.
- This inverse correlation suggests that MBL-MASP complexes do not possess a fixed stoichiometry.
Conclusions:
- Human MBL-MASP complexes exhibit significant inter-individual variation in composition.
- Findings support the existence of distinct populations of MBL-MASP-1 and MBL-MASP-2 complexes.
- The variable composition has implications for the functional capacity of the lectin pathway of complement.