Roxana Olguin-Alor

The role of CD5 as a regulator of T cell signaling and tolerance is well recognized. Recent data show expression of CD5 on different subtypes of human dendritic cells, however its functional relevance in modulating DC mediated responses remains poorly understood. In this study, we show CD5 is expressed on CD11c+ DC from murine thymus, lymph node, spleen, skin and lung. Although the development of DC subpopulations in CD5^-/- mice was normal, CD5-deficient DC produced significantly higher levels of IL-12 than wild type DC in response to LPS. CD5^-/- DC, in comparison to CD5^+/+ DC, enhanced the activation of CD4+ and CD8+ T cells in vitro and in vivo and induced significantly higher production of IL-2 and IFN-gamma by T cells. Consequently, CD5^-/- DC were significantly more potent than wild type DC in the induction of anti-tumor immunity and contact hypersensitivity responses in mice. Restoration of CD5 expression in CD5^-/- DC reduced IL-12 production and inhibited their capacity to stimulate T cells. Collectively, these data demonstrate that the specific expression of CD5 on DC inhibits the production of inflammatory cytokines and has a regulatory effect on their activity to stimulate T cells and induce immune responses. This study reveals a previously unrecognized regulatory role for CD5 on DC and provides novel insights into mechanisms for DC biology in immune responses.

Tilmicosin is an antimicrobial agent used to treat intramammary infections against S. aureus and has clinical anti-inflammatory effects. However, the mechanism by which it modulates the inflammatory process in the mammary gland is unknown. We evaluated the effect of tilmicosin treatment on the modulation of the mammary innate immune response after S. aureus infection and its effect on casein production in mammary epithelial cells. To achieve this goal, we used immortalized mammary epithelial cells (MAC-T), pre-treated for 12 h or treated with tilmicosin after infection with S. aureus (ATCC 27543). Our data showed that tilmicosin decreases intracellular infection (P ) and had a protective effect on MAC-T reducing apoptosis after infection by 80% (P ). Furthermore, tilmicosin reduced reactive oxygen species (ROS) (P ), IL-1β (P ), IL-6 (P ) and TNF-α (P ) production. In an attempt to investigate the signaling pathways involved in the immunomodulatory effect of tilmicosin, mitogen-activated protein kinase (MAPK) phosphorylation was measured by fluorescent activated cell sorting (FACS). Pre- treatment with tilmicosin increased ERK1/2 (P ) but decreased P38 phosphorylation (P ). In addition, the anti-inflammatory effect of tilmicosin helped to preserve casein synthesis in mammary epithelial cells (P ). This result indicates that tilmicosin could be an effective modulator inflammation in the mammary gland. Through regulation of MAPK phosphorylation, ROS production and pro-inflammatory cytokine secretion tilmicosin can provide protection from cellular damage due to S. aureus infection and help to maintain normal physiological functions of the bovine mammary epithelial cell.

We have previously reported that the absence of inhibins results in impaired dendritic cell (DC) maturation and function, leading to decreased T cell activation and diminished delayed‐type hypersensitivity responses. Here, we investigated the role of inhibins in peripheral regulatory T cell (Treg) induction in vitro and in vivo. Inhibin deficient (Inhα^−/−) mice showed an increased percentage of peripherally induced Tregs in colonic lamina propria and mesenteric lymph nodes, compared to Inhα^+/+ mice, which correlated with increased expression of PD‐L1 in CD103⁺ and CD8α⁺ DCs. Lipopolysaccharide‐stimulated bone marrow‐derived and ex vivo spleen‐ and lymph node‐purified CD11c⁺ Inhα^−/− DCs induced higher Tregs in vitro. Moreover, in vivo anti‐DEC205‐ovalbumin (OVA) DC targeting of mice with adoptively transferred OVA‐specific T cells showed enhanced induced peripheral Treg conversion in Inhα^−/− mice. These data identify inhibins as key regulators of peripheral T cell tolerance.

Inhibins are members of the TGFβ superfamily, which regulate many cellular processes including differentiation, proliferation, survival and apoptosis. Although initially described as hormones regulating the hypothalamus-pituitary-gonadal axis, based on their ability to antagonize Activins, our group has recently reported that they play a role in thymocyte differentiation and survival, as well as in thymic stromal cell maturation and nTreg generation. Here, we used Inhibin knock out mice (Inhα^-/-) to investigate the role of Inhibins in peripheral dendritic cell maturation and function. We first demonstrated that LPS treated Inhα^+/+ bone marrow derived dendritic cells (BMDC) were capable to produce significant levels of Inhibin A. Interestingly, Inhα^-/- BMDC showed reduced MHCII and CD86 upregulation and increased PD-L1 expression in response to LPS compared to Inhα^+/+, which correlated with reduced ability to induce proliferation of allogeneic T cells. The “semi-mature” phenotype displayed by Inhα^-/- mBMDC correlated with increased levels of IL-10 and slightly decreased IL-6 production after LPS stimulation. In addition, Inhα^-/- mBMDC showed impaired migration towards CCL19 and CCL21, assessed by in vitro chemotaxis and in vivo competitive homing experiments, despite their normal CCR7 expression. Furthermore, in vivo LPS-induced DC maturation was also diminished in Inhα^-/- mice, specially within the LC (CD207+ CD11b+ CD103-) subpopulation. Finally, analysis of delayed type hypersensitivity responses in Inhα^-/- mice, showed reduced ear swelling as a result of reduced cellular infiltration in the skin, correlating with impaired homing of CD207+ DCs to the draining lymph nodes. In summary, our data demonstrate for the first time that Inhibins play a key role in peripheral DC maturation and function, regulating the balance between immunity and tolerance.