Surrogate marker of intestinal permeability: serum concentrations of IgA and IgM against LPS of Gram (-) enterobacteria: Hafnia alvei, Pseudomonas aeruginosa, Morganella morganii, Proteus mirabilis, Pseudomonas putida, Citrobacter koseri, Klebsiella pneumonia. The gene discussed is CD40LG; the disease is Klebsiella pneumonia.