HSPD1 and chlamydia infectious disease: A nested case–control study consisting of 593 lung cancer cases and 671 controls evaluated the relationship of C. pneumoniae infection and lung cancer, using traditional serological markers such as microimmunofluorescence IgG and IgA antibodies and Chlamydia heat shock protein 60 antibodies (CHSP-60), which is a marker of chronic chlamydia infection.