This issue appears somewhat controversial because, whereas some investigators found that either isolated or combined low levels of IgG, IgM, and IgA were associated with a decreased survival [16,17,18,19,20] and Giomarellos-Bourboulis et al. [11] showed that the transition from severe sepsis to septic shock and death was marked by decreased blood levels of IgM, other authors reported different results; actually, in a recent meta-analysis (MA), Shankar-Hari et al. [21] demonstrated that low levels of IgG and IgM in septic patients were not associated with a poor outcome. This evidence concerns the gene CD40LG and Shock.