Role of microbiota in Crohn's disease induction in the light of studies of Human Microbiome Project

Crohn's disease (CD) is an inflammatory disorder which develops as a result of dysregulated interactions between gut microbiota and immune system. Because bacterial involvement in this illness is certain and classic methods of growing microorganisms are insufficient to clarify their impact on disease induction, metagenomics, as a culture-independent technique, provides revolutionary approach. This method become pivotal tool for a large project aiming at describing whole human microbiota - Human Microbiome Project (HPM). Studies on pathologically changed gut microbiota of CD patients involving metagenomic strategy provide profound analysis of intestinal microbial structure as well microbial localization. The review article also presents various aspects of the immune system functioning - such as genetic predispositions, dysregulated defensin secretion, poor epithelial barrier integrity, which contribute to improper immunological answer and promotion of inflammation.