C-C motif chemokine ligands 19 and 21 (CCL19, CCL21) were involved in NF-kappa B and chemokine signaling pathway while C-C motif chemokine ligand 5 (CCL5), C-C motif chemokine ligand 20 (CCL20), C-X-C motif chemokine ligand 1 (CXCL1), and C-X-C motif chemokine ligand 1 (CXCL3) played a role in both legionellosis and chemokine signaling pathway. Here, CCL21 is linked to legionellosis.