Anti-factor XIIa antibodies and methods of their use for the treatment of diseases related to factor XII such as diseases related to contact system activation, plasma prekallikrein signaling (eg, hereditary angioedema) and eye diseases It is disclosed in the specification. [Selection] Figure 4抗第XIIa因子抗体ならびに接触系活性化に関連する疾患、血漿プレカリクレインシグナル伝達(例えば遺伝性血管浮腫)および眼疾患などの第XII因子に関連する疾患の治療のためのそれらの使用方法を本明細書に開示する。【選択図】図4