TLR3 and neoplasm: revealed that the natural immune receptor TLR3 expressed by type II lung epithelial cells could identify the exosomal RNA secreted by tumor into the blood circulation (44–46), thus triggering the expressions of chemokines (CXCL1, CXCL2, CXCL5, and CXCL12) and recruiting neutrophils into the lungs (38).