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Here, we show that zinc addition in a serum- and lipopolysaccharide-free cell culture system leads to significantly enhanced levels of interleukin 1 beta ( IL-1 beta ) and tumour necrosis factor alpha ( TNF-alpha ) and to expression of the corresponding mRNA in human peripheral blood mononuclear cells ( PBMC ).
 mRNA, human peripheral blood mononuclear cells, TNF-alpha, tumour necrosis factor alpha, PBMC, IL-1 beta, interleukin 1 beta
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:
 mRNA, human peripheral blood mononuclear cells, TNF-alpha, tumour necrosis factor alpha, PBMC, IL-1 beta, interleukin 1 beta