8206
As part of the host ' s innate immune response , the release of reactive oxygen and nitrogen species by phagocytes represents a major obstacle to the establishment of infection .
 Chemical: oxygen; Chemical: nitrogen
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: oxygen; Chemical: nitrogen