 PTX3 activates the classical pathway of complement activation and facilitates pathogen recognition by macrophages and DCs.Human and murine PTX3, localized in the syntenic region of chromosome 3 (q24-28), are highly conserved, sharing 82% identical and 92% conserved amino acids.The human PTX3 gene is organized into three exons coding for the leader peptide (which is cleaved from the mature protein), the amino-terminal domain and the pentraxin domain of the protein.