The evaluation of IgM antibodies in the acute infection has been discussed since it still can be detected in chronic infection and there is a risk of false-positive results by cross-reactivity with antibodies, rheumatoid factor and other viral and bacterial diseases (Naot et al., 1981; Montoya, 2002; Bichara et al., 2012; Villard et al., 2012). This evidence concerns the gene CD40LG and bacterial infectious disease.