An inverse association between early contact with microbial compounds and respiratory allergies is well established.
Previous studies reported that the production of hBD2 and SLPI by epithelial cells was induced by various microbes, microbial compounds, and cytokines [ 18– 22].
An overview of volatile microbial compounds and their current detection methods has been given in recent publications (Schulz and Dickschat 2007; Kai et al. 2009; Korpi et al. 2009).
According to the data, having the bed in the living room was not significantly associated with measured microbial compounds and there was further no association with questionnaire based signs of mould and dampness at home (χ 2 -test, data not shown).
It is also important to note that many of these agonists and intracellular signalling responses affect other neutrophil functions, such as activation of the NADPH oxidase, release of granules and vesicles containing anti-microbial compounds, and prolongation of neutrophil survival.
The phylum Actinobacteria is composed of phylogenetically diverse organisms that have been primarily investigated for their ability to cause disease in plants and animals, to produce anti-microbial compounds and anti-tumour agents, and to degrade recalcitrant molecules in soil environments [ 20].
Several studies revealed that hBD2 is an important antimicrobial peptide, because it is expressed in epithelial cells in response to microbial compounds, microbes and cytokines [ 18– 21] and can inhibit several pathogenic bacteria [ 9], and Candida species [ 8].
However, the underlying mechanism, the cause-effect relationship, and particularly the identification of helpful individual microbes and microbial compounds remain to be established and discovered.
The genome of microbiome is 100 fold larger than the human genome, and microbial compounds give the major input to the bidirectional communication between the enteral neuron-immune system and the brain.
Among these, there are small compounds (like alkylamines and phosphoantigens) derived from stress-associated surface molecules as well as small bacterial metabolites or microbial compounds produced during infection and cellular stress.
For this reason, recent research has preferred the use of allergens such as dust mite, molds and microbial compounds including lipopolysaccharide (LPS), which show the neutrophilic inflammation, to the use of surrogate allergen ovalbumin (OVA).
