In the present study we quantified the presence of PTX3 in serum and stool samples of cases of culture proven shigellosis and studied the interplay between levels of PTX3 as a component of the innate immune response and the levels of anti-Shigella lipopolysaccharide (LPS) and anti-Shigella type 3 secretion system protein-Invasion plasmid antigen B (IpaB) antibodies in acute and convalescent phases of shigellosis. The gene discussed is PTX3; the disease is shigellosis.