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Infect. Immun. doi:10.1128/IAI.01172-06
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

LACTOBACILLUS PARACASEI SUBSPECIES PARACASEI B21060 SUPPRESSES HUMAN T CELL PROLIFERATION

Dipartimento di Medicina Interna, Università Tor Vergata, Rome, Italy; Bracco, SpA, Milan, Italy; Cattedra di Pediatria, Università Tor Vergata, Rome, Italy

^* To whom correspondence should be addressed. Email: Gi.Monteleone{at}Med.uniroma2.it.

	Abstract

Recent studies have shown that probiotics are beneficial in T cell-mediated inflammatory diseases. The molecular mechanism by which probiotics work remains elusive, but accumulating evidence indicates that probiotics can modulate immune cell responses. Since T cells express receptors for bacterial products/components, we examined whether different strains of lactobacilli directly regulate the functions of human T cells. CD4+ T cells were isolated from blood and intestinal lamina propria (LP) of normals and patients with inflammatory bowel disease (IBD). Mononuclear cells (MC) were also isolated from Peyer's patches (PP). Cells were activated with anti-CD3/CD2/CD28 in the presence or absence of Lactobacillus (L.) paracasei subspecies (subsp.) paracasei B21060, L. paracasei subsp. paracasei F19 or L. casei subsp. casei DG. Cell proliferation and death, Foxp3, intracellular pH, and cytokine production were evaluated by flow cytometry. We showed that L. paracasei subsp. paracasei B21060 but neither L. paracasei subsp. paracasei F19 nor L. casei subsp. casei DG inhibited blood CD4+ T cell growth. This effect was associated with no change in cell survival, expression of Foxp3, and production of IFN-, IL-4, IL-5 and IL-10. L. paracasei subsp. paracasei B21060-mediated blockade of CD4+T cell proliferation required a viable bacterium and was associated with decreased MCT-1 expression and low intracellular pH. L. paracasei subsp. paracasei B21060 also inhibited the growth of PPMC, normal and IBD CD4+ LP lymphocytes without affecting cytokine production. Data show that L. paracasei subsp. paracasei B21060 blocks T cell growth, thus suggesting a mechanism by which these probiotics could interfere with T cell-driven immune responses.