IL-10 Potentiates Differentiation of Human Induced Regulatory T Cells via STAT3 and Foxo1

Milk: a postnatal imprinting system stabilizing FoxP3 expression and regulatory T cell differentiation

BACKGROUND

Breastfeeding has protective effects for the development of allergies and atopy. Recent evidence underlines that consumption of unboiled farm milk in early life is a key factor preventing the development of atopic diseases. Farm milk intake has been associated with increased demethylation of FOXP3 and increased numbers of regulatory T cells (Tregs). Thus, the questions arose which components of farm milk control the differentiation and function of Tregs, critical T cell subsets that promote tolerance induction and inhibit the development of allergy and autoimmunity.

FINDINGS

Based on translational research we identified at least six major signalling pathways that could explain milk's biological role controlling stable FoxP3 expression and Treg differentiation: (1) via maintaining appropriate magnitudes of Akt-mTORC1 signalling, (2) via transfer of milk fat-derived long-chain ω-3 fatty acids, (3) via transfer of milk-derived exosomal microRNAs that apparently decrease FOXP3 promoter methylation, (4) via transfer of exosomal transforming growth factor-β, which induces SMAD2/SMAD3-dependent FoxP3 expression, (5) via milk-derived Bifidobacterium and Lactobacillus species that induce interleukin-10 (IL-10)-mediated differentiation of Tregs, and (6) via milk-derived oligosaccharides that serve as selected nutrients for the growth of bifidobacteria in the intestine of the new born infant.

CONCLUSION

Accumulating evidence underlines that milk is a complex signalling and epigenetic imprinting network that promotes stable FoxP3 expression and long-lasting Treg differentiation, crucial postnatal events preventing atopic and autoimmune diseases.

Roles of regulatory T cells in cancer immunity

CD4(+) regulatory T cells (Tregs) expressing the transcription factor FoxP3 are highly immune suppressive and play central roles in the maintenance of self-tolerance and immune homeostasis, yet in malignant tumors they promote tumor progression by suppressing effective antitumor immunity. Indeed, higher infiltration by Tregs is observed in tumor tissues, and their depletion augments antitumor immune responses in animal models. Additionally, increased numbers of Tregs and, in particular, decreased ratios of CD8(+) T cells to Tregs among tumor-infiltrating lymphocytes are correlated with poor prognosis in various types of human cancers. The recent success of cancer immunotherapy represented by immune checkpoint blockade has provided a new insight in cancer treatment, yet more than half of the treated patients did not experience clinical benefits. Identifying biomarkers that predict clinical responses and developing novel immunotherapies are therefore urgently required. Cancer patients whose tumors contain a large number of neoantigens stemming from gene mutations, which have not been previously recognized by the immune system, provoke strong antitumor T-cell responses associated with clinical responses following immune checkpoint blockade, depending on the resistance to Treg-mediated suppression. Thus, integration of a strategy restricting Treg-mediated immune suppression may expand the therapeutic spectrum of cancer immunotherapy towards patients with a lower number of neoantigens. In this review, we address the current understanding of Treg-mediated immune suppressive mechanisms in cancer, the involvement of Tregs in cancer immunotherapy, and strategies for effective and tolerable Treg-targeted therapy.

Murine Sertoli cells promote the development of tolerogenic dendritic cells: a pivotal role of galectin-1

Sertoli cells (SCs) possess inherent immunosuppressive properties and are major contributors to the immunoprivileged status of mammalian testis. SCs have been reported to inhibit the activation of B cells, T cells and natural killer cells but not dendritic cells (DCs). Herein, we present evidence that co-culture with SCs results in a persistent state of DC immaturity characterized by down-regulation of the surface molecules I-A/E, CD80, CD83, CD86, CCR7 and CD11c, as well as reduced production of pro-inflammatory cytokines. SC-conditioned DCs (SC-DCs) displayed low immunogenicity and enhanced immunoregulatory functions, including the inhibition of T-cell proliferation and the promotion of Foxp3(+) regulatory T-cell development. Mechanistically, the activation of p38, extracellular signal-regulated kinase 1/2, and signal transducer and activator of transcription 3 was suppressed in SC-DCs. More importantly, we demonstrate that galectin-1 secreted by SCs plays a pivotal role in the differentiation of functionally tolerogenic SC-DCs. These findings further support the role of SCs in maintaining the immunoprivileged environment of the testis and provide a novel approach to derive tolerogenic DCs, which may lead to alternative therapeutic strategies for the treatment of immunopathogenic diseases.

Maternal immunity and pregnancy outcome: focus on preconception and autophagy

Modulation of the maternal immune system before conception has a major role in determining subsequent pregnancy outcome. However, this has been a neglected area of investigation. There is a correlation between the length of time a woman is exposed to semen from her male partner and the development of regulatory T cells that limit a maternal antifetal immune response. Similarly, the composition of the vaginal microbiota influences the capacity of microorganisms to bypass the cervical barrier and colonize the uterus before pregnancy. The extent that this preconception colonization influences pre- and post-implantation gestational events depends on the types of microbes present, the genetic make-up of the mother and environmental influences on the magnitude and direction of her immune responses. Prepregnancy uterine and placental colonization with commensal bacteria may be beneficial to the fetus and newborn by generating tolerance to organisms that enhance postnatal well-being. Efforts to prevent or stop the progression of premature myometrial contractions have been limited because of an incomplete understanding of the mechanism(s) that trigger this occurrence. Based on recent studies of autophagy during gestation and parturition, inhibition of autophagy in myometrial cells may be the critical factor leading to a sequence of events culminating in induction of myometrial contractions either prematurely or at term.