However, in 12 of the 15 Q fever cases that had paired serum available for examination, 0 (0%) and 4 (33.3%) cases were seropositive for M. pneumoniae IgM based on results from the ELISA kits used in this study and others (NovaTec Immundiagnostica GmbH, Germany), respectively (data not shown). The gene discussed is CD40LG; the disease is Q fever.