BACKGROUND: 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. OBJECTIVE: Because the role of the ficolin-LP during edematous attacks is still enigmatic, we analyzed its activity during such episodes. METHODS: 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 35 samples 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. RESULTS: 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 of the attack until blood sampling. CONCLUSIONS: 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.
Journal of Allergy and Clinical Immunology, 2014, Vol 134, Issue 6, p. 1388-1393