title: Discrete MBL-MASP complexes show wide inter-individual variability in concentration: data from UK vs Armenian populations.
abstract: Mannan-binding lectin (MBL) circulates in plasma in complex with MBL-associated serine proteases (MASP) -1, -2 and -3 and a smaller component, MAp19. When MBL binds to the surface of foreign material (microorganisms), MASP-1, -2, -3 are activated. MASP-2 then activates the complement system. MASP-1 and -3 may activate other (unidentified) systems. MBL levels, MBL-bound MASP-1 and MBL-bound MASP-2 activities have been evaluated in healthy individuals from UK and Armenian populations. MBL-bound MASP-2 activity declines in aging (P<0.04). MBL correlates with smoking (P<0.02). There were significant differences between the two populations in MBL-bound MASP-1 activity and in MBL, but no difference in MBL-bound MASP-2 activity. When MASP activities were normalised to MBL (i.e. MASP-1 activity/MBL, MASP-2 activity/MBL), normalised MASP-2 activity in UK individuals was more than 2 fold higher than in Armenians. The difference in normalised MASP-2 activity level between these two Caucasoid populations, suggests that concentration of the MBL-(MASP-2) complex, and therefore the function of activating complement, depends not only on the quantity of MBL in serum and its oligomeric state, but also on the quantity of MASP-2 in serum. It is likely that in individuals with high MBL concentration there is excess free MBL not occupied by MASPs, particularly not by MASP-2.
authors.affiliation: MRC Immunochemistry Unit, Department of Biochemistry, Oxford University, Oxford, UK.
authors.forename: K R
authors.initials: KR
authors.lastname: Mayilyan
authors.forename: J S
authors.initials: JS
authors.lastname: Presanis
authors.forename: J N
authors.initials: JN
authors.lastname: Arnold
authors.forename: R B
authors.initials: RB
authors.lastname: Sim
mesh_terms: D000328:Adult; D001136:Armenia; D005260:Female; D006801:Humans; D008297:Male; D037241:Mannose-Binding Lectins / Q000097:blood*; D050606:Mannose-Binding Protein-Associated Serine Proteases / Q000032:analysis*; D012907:Smoking / Q000097:blood; D006113:United Kingdom
chemical_list: D037241:Mannose-Binding Lectins; C084067:MASP1 protein, human; C105296:MASP2 protein, human; D050606:Mannose-Binding Protein-Associated Serine Proteases