Consequently, more specific investigations were performed, and serological tests for infective endocarditis of diverse etiology were acquired, including IgG and IgM antibodies for Mycoplasma pneumoniae, Bartonella henselae, Chlamydophila pneumoniae, Brucella spp., Legionella pneumophila, and Coxiella burnetii. This evidence concerns the gene CD40LG and infective endocarditis.