The present invention relates, in general, to development of non-human transgenic animals expressing a human blood clotting factor, such as Factor VIII, Factor VII, Factor IX and von Willebrand factor. The invention further provides methods of detecting immunogenic events against human blood clotting factor using the transgenic animals described.本發明大體而言係關於表現諸如因子VIII、因子VII、因子IX及溫韋伯氏因子之人類凝血因子之非人類基因轉殖動物的開發。本發明進一步提供使用所述基因轉殖動物偵測針對人類凝血因子之免疫原性事件的方法。