6503
An immunoperoxidase reaction , PAP method , with the antiserum of Factor VIII as the primary antibody , was carried out in the endometrial biopsies to detect the Factor VIII activity in the endometrial endothelium before and after insertion of LNG - IUD - 20 .
 immunoperoxidase, PAP, Factor VIII, Factor VIII
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 immunoperoxidase, PAP, Factor VIII, Factor VIII