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Mutations in Factor XII, plasminogen gene, angiopoietin-1 gene and kininogen 1 gene have been found in some patients with hereditary angioedema with normal C1 inhibitor (HAE-nl-C1inh), but the underlying disease mechanisms remain unclear. Additionally, there are no accepted biomarkers for this disease. Because the contact system has been implicated in hereditary angioedema with C1 inhibitor deficiency (HAE-C1inh), we studied the fragmentation patterns of serum glycoprotein 120 (sgp120), a protein that is highly susceptible to cleavage by kallikrein, in 31 HAE-C1inh and 13 HAE-nl-C1inh patient plasma samples. Compared to normal controls, the majority of plasma samples from patients with HAE-C1inh contained fragmented sgp120. These samples also showed increased kallikrein amidolytic activity indicating spontaneous contact system activation. In contrast, most samples from HAE-nl-C1inh patients exhibited intact sgp120. However, if these samples were incubated at 4 °C in plastic, significant sgp120 fragmentation and spontaneous contact system activation were observed. Concurrently, there was C1 inhibitor fragmentation that generated the nonfunctional 94 kD fragment and a reduction in C1 inhibitor function. Normal samples did not show sgp120 or C1 inhibitor fragmentation after incubation. We sequenced sgp120 and found it to be identical to inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4). These results suggest that sgp120 or ITIH4 is cleaved when the contact system is activated and that this cleavage could be used as a biomarker in patients with HAE-nl-C1inh.

Hereditary angioedema (HAE) attacks are caused by excessive activation of the contact system. Understanding how the contact system is activated in HAE, especially in patients with normal C1 inhibitor (HAEnCI), is essential to effectively treat this disease. Contact system activation involves the cleavage of several proteins including Factor XII (FXII), high molecular weight kininogen (HK), prekallikrein, sgp120 (ITIH4) and C1 inhibitor (C1-INH) before the subsequent generation of bradykinin that mediates HAE. In this study, we evaluated the fragmentation and enzymatic activity of contact system proteins in HAEnCI plasma samples before and after contact system activation induced by incubation in the cold. Our results show that in contrast to normal plasma, cold activation induced contact system activation in the majority of the HAEnCI patient samples we tested, in which each contact system protein exhibited fragmentation, FXII and kallikrein enzymatic activity increased, and C1-INH functional activity decreased. HAEnCI samples with low FXII concentrations or functional activity were not affected by cold activation. One HAEnCI sample with a plasminogen gene mutation activated the fibrinolytic system, as shown by an increase in concentration of plasma D dimers. Our results suggest that cold activation seems to be initiated by the cleavage of prekallikrein, and that it needs FXII in order to occur. Reported to be susceptible to excessive contact system activation after incubation in the cold, we further applied this system of study to the evaluation of plasma from women undergoing estrogen treatment. Similar to plasma from HAEnCI patients, excessive contact system activation was demonstrated.

The processes of isolation and sterilization of intravenous gamma globulin (IVIG) affect the end product characteristics and, therefore, its tolerability. Different products have different incidences of adverse reactions. The aim of this study was to quantify the immediate adverse events (AE) caused by the different IVIG preparations. We analyzed 1 395 infusions in 28 patients, with a median of 32.5 per subject (range 2-214), using six different IVIG preparations, with an average dose 40.3 ± 8.3 g. One thousand and thirty-one infusions were analyzed retrospectively and 364 prospectively. Patients used a mean of 2.68 ± 1.8 different IVIGs, with a median of 2 (range 1-6) per person. The number of trademarks used was related to the number of infusions received, r = 0.73. AE presented in 24 (2.3%) of 1 031 infusions retrospectively analyzed, affecting 11 of 23 patients enrolled, with a mean of 2.18 ± 1.08 AE per subject. Of 24 patients and 364 infusions prospectively analyzed, AE were observed in 14 patients and in 32 (7.2%) procedures. Twenty-four (42.9%) of 56 AE were mild, 31 (55.5%) moderate and one (1.8%) severe. The infusion rate was 9.04 ± 6 g/h for those presenting AE vs. 10.6 ± 4.6 g/h for those who did not (p = 0.31, NS). The incidence, severity and proportion of patients with AE for each brand of IVIG were very different from each other. This information should be taken into account when selecting the IVIG to be used.