Ptx3, also known as tumor necrosis factor-stimulated gene sequence-14 (TSG14), is a secreted pattern-recognition receptor that has a non-redundant role in resistance to selected microbial agents. Ptx3 belongs to the family of “long pentraxins”, which have C-terminal pentraxin domains and novel amino-terminal domains. Ptx3 binds selected pathogens, including Aspergillus fumigatus, Pseudomonas aeruginosa and Salmonella typhimurium. It is synthesized in IgA glomerulonephritis and activates mesangial cells.