Activation of the ficolin-lectin pathway during attacks of hereditary angioedema

Abstract

The activation of plasma enzyme systems is insufficiently controlled in hereditary angioedema due to the deficiency of C1-inhibitor (C1-INH) (HAE-C1-INH). Recently, it was suggested that the ficolin-lectin pathway (ficolin-LP) might play a more dominant role than the mannose-binding lectin-lectin pathway in the pathomechanism of HAE-C1-INH. Because the role of the ficolin-LP during edematous attacks is still enigmatic, we analyzed its activity during such episodes. Thirty-five patients with HAE-C1-INH, who have experienced severe attacks on 106 occasions, were enrolled. We analyzed blood samples drawn during attacks, and obtained 35samples from the same patients during symptom-free periods. The serum levels of ficolin-2, ficolin-3, MASP-2, ficolin-3/MASP-2 complex, C1-INH, and C4, as well as the extent of ficolin-3-mediated terminal complement complex (FCN3-TCC) deposition, were measured using ELISA-based methods. Levels of MASP-2 and of the ficolin-3/MASP-2 complex were elevated (P< .0001 and .033, respectively), whereas that of FCN3-TCC was lower (P< .0001) during attacks than during the symptom-free period. During symptom-free periods, FCN3-TCC deposition was significantly related to concentrations of ficolin-3 (R= 0.2778; P= .0022), antigenic C1-INH (R= 0.3152; P=.0006), and C4 (R= 0.5307; P< .0001). Both ficolin-3 and MASP-2 levels correlated inversely with the time from the onset ofthe attack until blood sampling. There is a marked heterogeneity of the pathomechanism and development of hereditary angioedema attacks in different patients. Our results suggest that the activation of the ficolin-LP may deplete the innately low level of C1-INH and thus, it may contribute to the uncontrolled activation of plasma cascade systems, and thereby to edema formation.