Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2011 Aug;6(3):261-74.
doi: 10.1007/s12263-011-0218-x. Epub 2011 Apr 16.

The Immunomodulatory Properties of Probiotic Microorganisms Beyond Their Viability (Ghost Probiotics: Proposal of Paraprobiotic Concept)

Free PMC article

The Immunomodulatory Properties of Probiotic Microorganisms Beyond Their Viability (Ghost Probiotics: Proposal of Paraprobiotic Concept)

Valentina Taverniti et al. Genes Nutr. .
Free PMC article


The probiotic approach represents a potentially effective and mild alternative strategy for the prevention and treatment of either inflammatory or allergic diseases. Several studies have shown that different bacterial strains can exert their probiotic abilities by influencing the host's immune system, thereby modulating immune responses. However, the emerging concern regarding safety problems arising from the extensive use of live microbial cells is enhancing the interest in non-viable microorganisms or microbial cell extracts, as they could eliminate shelf-life problems and reduce the risks of microbial translocation and infection. The purpose of this review is to provide an overview of the scientific literature concerning studies in which dead microbial cells or crude microbial cell fractions have been used as health-promoting agents. Particular attention will be given to the modulation of host immune responses. Possible mechanisms determining the effect on the immune system will also be discussed. Finally, in the light of the FAO/WHO definition of probiotics, indicating that the word 'probiotic' should be restricted to products that contain live microorganisms, and considering the scientific evidence indicating that inactivated microbes can positively affect human health, we propose the new term 'paraprobiotic' to indicate the use of inactivated microbial cells or cell fractions to confer a health benefit to the consumer.


Fig. 1
Fig. 1
Interaction between host immune system and cellular components of probiotic bacteria. a Molecules or fractions from Lactobacillus cells demonstrated to activate host immune and epithelial cells. b Immunomodulatory molecules or fractions isolated from other probiotic bacterial cells. Cytokines, immunological activities or cell factors that have been inhibited are indicated in a red rectangle, while those that have been enhanced are in a green rectangle. The immunomodulatory activities shown in the picture have been experimentally proven only for certain strains/species inside a bacterial group: consult the references cited in the article for more details. GroEL is a chaperone protein (heat-shock protein) found in many bacteria; BopA is a cell surface lipoprotein identified in Bifidobacterium bifidum, which has been demonstrated to promote the adhesion of the bacterium on Caco-2 cells. DC-SIGN dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin, ERK extracellular-signal-regulated kinase, IL interleukin, LPS lipopolysaccharide from Escherichia coli, NF-κB nuclear factor kappa-light-chain-enhancer of activated B cells, NO nitric oxide, NOD2 nucleotide-binding oligomerisation domain containing, ROS reactive oxygen species, TLR Toll-like receptor, TNF-α tumour necrosis factor-α

Similar articles

See all similar articles

Cited by 59 articles

See all "Cited by" articles