TFF2 and legionellosis: The association of C2 TFF2+ TCs primarily pertained to the biological processes related to hypoxia response, decreased oxygen levels response, oxygen levels response, cellular response to decreased oxygen levels, and cellular response to hypoxia in GO-BP, and was associated with the estrogen signaling pathway, HIF-1signaling pathway, legionellosis, lipid and atherosclerosis and the glycolysis pathways correlation in KEGG.