3935
Cystic fibrosis (CF) patients develop progressive cytokine -mediated inflammatory lung disease , with abundant production of thick, tenacious, protease -and oxidant-rich purulent airway secretions that are difficult to clear even with physiotherapy .
 protease, cytokine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 protease, cytokine