The immunologic tone of the intestinal tract is one of suppressed or highly regulated responses. While there are several components (intrinsic and extrinsic to the gut-associated lymphoid tissue) responsible for this immunologically suppressed tone, the intestinal epithelial call (IEC) has been proposed as a key player in this process. IECs can take up and process antigen but distinct surface molecules and restriction elements allow them to present these antigens to unique regulatory T cells. These include the expression of the class Ib molecule CD1d as well as a novel CD8 ligand, gp180. These molecules come together to activate a subpopulation of CD8+ regulatory cells whose function is to suppress immune responses in an antigen non-specific fashion most likely through cognate interactions. This form of regulation may be unique to the gut-associated lymphoid tissue which is consistent with the unusual demands upon this part of the immune system.
"The interaction of LAB with M cells induces mainly specific immune responses (Neutra & Kraehen Buhl, 1992), while the interaction with FAE cells induces a non-specific or inflammatory response, even though this mode of entry can also enhance the specific immune response. The interaction with epithelial cells can lead to enhancement of local immunity or non-response by antigen clearance (Campbell et al., 1999; Hershberg & Mayer, 2000). These studies have also demonstrated the importance of the ecological niche of the microorganism probiotic to elicit a better immunological effect on the small or large intestine (Vintiñi et al, 2000). "
[Show abstract][Hide abstract] ABSTRACT: Health claims of lactic acid bacteria (LAB) used in functional foods and pharmaceutical preparations are based on the capacity of these microorganisms to stimulate the host immune system. In this study, the antigenic effect of LAB (Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus) on the gut immune system of BALB/c mice was evaluated. A dose-dependent increase of the Bcl2 protein was observed with all LAB assayed. Furthermore, the analysis of cytokine-producing cells in the lamina propria of gut showed that TNFalpha and INFgamma values, determined in macrophages cultured from Peyer patches, were enhanced for all the LAB assayed. An important increase of interleukins IL-10 and IL-4 was observed mainly in mice fed with Lactobacillus delbrueckii ssp. bulgaricus or Lactobacillus casei, while a significant induction of IL-2 and IL-12 was only observed with L. acidophilus (P<0.01). These effects were dose dependent. The role of produced cytokines in the balance Th1/Th2 was determined by a systemic antibody response against parenterally injected ovoalbumin. L. casei, L. delbrueckii ssp. bulgaricus and L. acidophilus enhanced the IgG1 response favouring Th2 balance, while L. acidophilus also increased the IgG2a response inducing Th1 balance. S. thermophilus did not influence the balance Th1/Th2. Our studies showed that lactic acid bacteria induce distinct mucosal cytokine profiles showing different adjuvant capacity among them. Thus, selection of probiotic strain with immunological properties must be well defined to influence cytokine expression that favour the claimed immune response.
European Journal of Clinical Nutrition 12/2002; 56 Suppl 4(S4):S21-6. DOI:10.1038/sj.ejcn.1601658 · 2.71 Impact Factor
"Second, enterocytes play a role in antigen recognition and presentation, and the resulting development of tolerance, anergy or responsiveness to foreign molecules. This function is achieved through the expression of toll-like receptors (allows for recognition of conserved antigen sequences; Cario et al., 2002), and expression of MHC I and II (allows for antigen presentation; Bland and Kambarage, 1991; Campbell et al., 1999). The ability to recognize and respond appropriately to the diverse array of orally-derived antigen entering the GI tract is incredibly important, given the large number of innocuous antigens that are found in this anatomical region and the requisite tolerance that must be developed to certain antigens (e.g., food components). "
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