They are commonly
used to manufacture fermented milk products and some species are considered probiotics. Many health benefits are associated with their use, including the ability to modulate the immune system (Gill, Midostaurin supplier 1998; Salminen et al., 1998) as well as antitumor, antimetastatic properties (Tomita et al., 1994; Matsuzaki et al., 1996). Intraperitoneal administration of Lactobacillus casei induced the production of cytokines such as interferon γ (IFNγ), interleukin-1 (IL-1) and tumor necrosis factor α (TNFα), which could contribute to the inhibition of tumor growth and increased survival of tumor-bearing mice (Matsuzaki, 1998). Several Lactobacillus species stimulate cells of the innate immune system in vitro, namely natural killer cells (Kato find more et al., 1984; Haller et al., 1999) and macrophages. Stimulation of these cells can induce proinflammatory cytokines such
as TNFα (Haller et al., 1999), IFNγ and IL-12 (Miettinen et al., 1998; Hessle et al., 1999; Kato et al., 1999; Morita et al., 2002), and regulatory cytokines such as IL-10 (Christensen et al., 2002). TNFα directly induces tumor apoptosis and enhances the tumoricidal activity of macrophages (Wang et al., 1996), while IL-12 has potent antitumor and antimetastatic effects against tumors by the stimulation of cytotoxic CD8+ T cells and natural killer cells. IL-12 also enhances the production of Th1 cytokines such as IFNγ. IL-10 plays a regulatory role in allergy (Akbari et al., 2001) and anti-inflammatory responses
(Kuhn et al., 1993). Toll-like Avelestat (AZD9668) receptors (TLRs) are pattern recognition receptors that recognize molecules that are common to pathogens, but absent in the host. TLR4 is essential for the recognition of lipopolysaccharide, while lipoproteins from gram-positive bacteria are recognized by TLR2 (Takeuchi et al., 1999). Major cell wall components of gram-positive bacteria, such as peptidoglycan and lipoteichoic acid, signal through TLR2 (Schwandner et al., 1999; Matsuguchi et al., 2003) and stimulate cytokine production. The mannose and Fcγ receptors and CD14 are associated with bacterial phagocytosis, which can also result in cytokine production. Unmethylated CpG dinucleotides in the bacterial DNA have stimulatory effects on mammalian immune cells (Lipford et al., 1998). Hemmi et al. (2000) showed that the cellular response to CpG DNA is mediated by TLR9 as TLR9 knockout mice did not respond to CpG DNA and the immune cells from these mice did not produce inflammatory cytokines upon stimulation with CpG DNA. This study aims to evaluate the immunostimulatory properties of three commonly consumed lactobacilli species: L. casei, Lactobacillus rhamnosus and Lactobacillus bulgaricus. Analysis of splenocyte TNFα, IL-12p40 and IL-10 production after stimulation with ‘live’ and lyophilized lactobacilli was performed. The role of TLRs and phagocytosis in the stimulation of cytokine production was also examined.