Immunogenics: extracellular bacterial compounds as mediators of lactic acid bacteria-target cell interaction

Abstract

Probiotic microorganisms able to regulate the immune system (immunobiotics) are generally selected from lactic acid bacteria (LAB) strains (Marco et al. 2006; Kitazawa et al. 2008). The tightening of legislation in several countries for probiotic health claims has led to continued scientifi c and industrial interest to unravel the molecular mechanisms responsible for the observed beneficial probiotic traits. The beneficial effects of immunobiotic lactobacilli have been demonstrated in several in vitro and in vivo studies, which revealed a variety of host effects and generated several hypotheses about the mechanisms by which immunobiotics infl uence their hosts (Lebeer et al. 2008; Villena et al. 2011; Bron et al. 2012). In this chapter, we describe the probiotic molecules and cognate host signaling and response cascades that are proposed to modulate gut barrier and immune function. In particular, we discuss the emerging insights about the ability of immunobiotics secreted proteins to regulate immune responses in the gut. Furthermore, we discuss recent data that highlights the role of lipid rafts in the immunoregulatory activity of immunobiotics secreted proteins.