# Probiotic Molecules That Inhib Inflammatory Diseases
## 5 Mechanism by Which EPS\({}^{\text{Bs}}\) Inhibits Inflammation
### Immune Regulator Molecules  
1. TLR4. The anti-inflammatory effect of EPS\({}^{\text{Bs}}\) requires TLR4, as shown in the disease models for colitis [12], bacterial sepsis [11], and GvHD [7]. The requirement for TLR4 resides in the macrophages and DCs [7; 10; 12], but TLR4 on other cell types, e.g., epithelial cells, mesenchymal, and NK cells, may also be required for, or contribute to, the protection by EPS\({}^{\text{Bs}}\). Experiments with cell-specific knockout mice will establish the identity of TLR4\({}^{+}\) cells required for the anti-inflammatory activity of EPS\({}^{\text{Bs}}\). The finding that EPS\({}^{\text{Bs}}\) induces an anti-inflammatory effect through TLR4 is, of course surprising, because TLR4 signaling is associated with an inflammatory response due to LPS signaling. Although LPS is generally associated with pro-inflammatory responses, LPS can also induce tolerance, known as low dose tolerance or endotoxin tolerance. In this case, prolonged administration of LPS [74], or a single low dose of LPS, can dampen inflammation and induce tolerance. The mechanism by which this occurs remains under investigation [75]. Other TLR4-mediated anti-inflammatory responses have also been described and in these cases, the immunoregulatory effect is often mediated by other receptors. For example, the toll-like receptor family protein RP105/MD1 complex is involved in the immunoregulatory effect of EPS\({}^{\text{LP}}\) from Lactobacillus plantarum N14, which inhibits inflammatory TLR4 signaling [51]. Furthermore, [PERSON] et al. showed that soluble CD83 inhibits T cell activation by binding to the TLR4/MD-2 complex on CD14\({}^{+}\) monocytes and altering the signaling cascade to induce the production of anti-inflammatory molecules IDO and IL-10 [76]. [PERSON] et al. showed that the lectin DC-SIGN modulates TLR signaling via Raf-1 kinase-dependent acetylation of the transcription factor NF-kB, which increased the anti-inflammatory response by increasing the transcription of IL-10 [77]. Furthermore, [PERSON] et al. showed that leukadherin-1-mediated activation of CD110 inhibits LPS-induced pro-inflammatory responses in macrophages and protects mice from endotoxic shock by blocking LPS-TLR4 interaction [78]. Lastly, [PERSON] et al. showed that galectin-3 is a negative regulator of LPS-mediated inflammation [79]. We hypothesize that EPS\({}^{\text{Bs}}\) also engages a receptor that negatively regulates TLR4-mediated signaling. 2. TGF-\(\beta\) and PD-L1. [PERSON] et al. showed that EPS\({}^{\text{Bs}}\)-induced peritoneal M2 macrophages inhibit proliferation and activation of both CD4\({}^{+}\) and CD8\({}^{+}\) T cells activated with anti-CD3 and anti-CD28 antibodies, _in vitro_[10]. M2 macrophages are known to mediate an anti-inflammatory response by several molecules, including TGF-\(\beta\), Arg-1, IL-10, PD-L1, and PD-L2. EPS\({}^{\text{Bs}}\)-induced peritoneal M2 macrophages inhibited T cells in a contact-dependent manner, and this inhibition was dependent on TGF-\(\beta\) in the case of CD4\({}^{+}\) T cells and on TGF-\(\beta\) and PD-L1 in the case of CD8\({}^{+}\) T cells [10]. EPS\({}^{\text{Bs}}\)-induced peritoneal M2 macrophages also upregulated Arg-1 and secretion of IL-10, and although these molecules were not required for the inhibition of T cell proliferation and activation _in vitro_, we predict that they are involved in the EPS\({}^{\text{Bs}}\)-induced anti-inflammatory response _in vivo_. 3. IDO. [PERSON] et al. showed that EPS\({}^{\text{Bs}}\) induces inhibitory BMDCs that completely inhibited alloreactive T cell proliferation in an MLR [7]. This inhibition was neither dependent on TGF-\(\beta\) or PD-L1, nor on other inhibitory molecules, such as Arg-1, IL-10, CTLA4, and PD-L2. Instead, the EPS\({}^{\text{Bs}}\)-induced BMDCs inhibited alloreactive T cells in the MLR through the inhibitory molecule, IDO [7].