The role of ficolins and MASPs in hereditary angioedema due to C1-inhibitor deficiency

Background and ObjectiveHereditary angioedema due to C1-inhibitor deficiency (HAE-C1-INH) causes disturbances in the complement system. However, the influence of HAE-C1-INH on the lectin pathway of complement is unresolved. Thus, we studied the main initiator molecules, enzymes and regulators in the lectin pathway in patients with HAE-C1-INH.MethodsThe serum concentrations of ficolin-2, ficolin-3, MBL, MASP-2, MASP-3, and MAP-1 were measured during symptom-free periods in 91 patients with HAE-C1-INH, and in 100 healthy controls using sandwich ELISAs.ResultsCompared with controls, the levels of ficolin-2 (p < 0.0001) and MASP-2 (p = 0.0238) were reduced, while the levels of MBL and MASP-3 were elevated (p = 0.0028 and p < 0.0001, respectively) in HAE-C1-INH patients. Ficolin-3 and MAP-1 levels did not differ significantly between the two groups. Ficolin-2 correlated with MASP-3 in patients (r = 0.3443, p = 0.0008), while these parameters showed an opposite relationship in controls (r = −0.4625, p < 0.0001). In the patients, ficolin-3 correlated with MASP-2 (r = 0.3698, p = 0.001). Ficolin-2, -3, and MAP-1 correlated negatively with the annual requirement of plasma derived C1-INH concentrate (r = −0.2863, p = 0.0059; r = −0.2654, p = 0.0110 and r = −0.2501, p = 0.0168, respectively). Ficolin-3 showed a negative correlation with the annual number of attacks (r = −0.2478, p = 0.0179).ConclusionsWe found significant differences between patients and controls in the levels of some of the molecules belonging to the lectin complement pathway. Low concentrations of particularly ficolin-2 and -3 were inversely correlated with the severity of HAE-C1-INH, while this was not observed for MBL. This suggests a previously unrecognized involvement of the ficolin-dependent lectin complement pathway in the pathophysiology of HAE-C1-INH.

► The lectin pathway parameters were different between HAE patients and controls.
► Severe hereditary angioedema is associated with lower ficolin-2 and ficolin-3 levels.
► Our results suggest the involvement of the ficolin–lectin pathway in HAE.
► Our study may contribute to clarifying the role of ficolin–lectin pathway in HAE.