Induction of Immune Tolerance to Dietary Antigens

Oral Tolerance Development and Maintenance

The gastrointestinal tract has an abundant mucosal immune system to develop and maintain oral tolerance. The oral route of administration takes advantage of the unique set of immune cells and pathways involved in the induction of oral tolerance. Food allergy results from a loss of oral tolerance toward ingested antigens. Oral immunotherapy is thought to initiate desensitization through interaction of an allergen with mucosal dendritic cells that initiate downstream immune system modulation through regulatory T cells and effector T cells.

Murine models for mucosal tolerance in allergy

Immunity is established by a fine balance to discriminate between self and non-self. In addition, mucosal surfaces have the unique ability to establish and maintain a state of tolerance also against non-self constituents such as those represented by the large numbers of commensals populating mucosal surfaces and food-derived or air-borne antigens. Recent years have seen a dramatic expansion in our understanding of the basic mechanisms and the involved cellular and molecular players orchestrating mucosal tolerance. As a direct outgrowth, promising prophylactic and therapeutic models for mucosal tolerance induction against usually innocuous antigens (derived from food and aeroallergen sources) have been developed. A major theme in the past years was the introduction of improved formulations and novel adjuvants into such allergy vaccines. This review article describes basic mechanisms of mucosal tolerance induction and contrasts the peculiarities but also the interdependence of the gut and respiratory tract associated lymphoid tissues in that context. Particular emphasis is put on delineating the current prophylactic and therapeutic strategies to study and improve mucosal tolerance induction in allergy.

Differential transcriptome of tolerogenic versus inflammatory dendritic cells points to modulated T1D genetic risk and enriched immune regulation

Tolerogenic dendritic cells (tolDCs) are assessed as immunomodulatory adjuvants to regulate autoimmunity. The underlying gene expression endorsing their regulatory features remains ill-defined. Using deep mRNA sequencing, we compared transcriptomes of 1,25-dihydroxyvitaminD₃/dexametasone-modulated tolDCs with that of non-modulated mature inflammatory DCs (mDCs). Differentially expressed genes controlled cellular interactions, metabolic pathways and endorse tolDCs with the capacity to regulate cell activation through nutrient and signal deprivation, collectively gearing tolDCs into tolerogenic immune regulators. Gene expression differences correlated with protein expression, designating low CD86 and high CD52 on the cell surface as superior discriminators between tolDCs and mDCs. Of 37 candidate genes conferring risk to developing type 1 diabetes (T1D), 11 genes differentially expressed in tolDCs and mDCs regulated immune response and antigen-presenting activity. Differential-expressed transcripts of candidate risk loci for T1D suggest a role of these 'risk genes' in immune regulation, which targeting may modulate the genetic contribution to autoimmunity.

Deciphering the black box of food allergy mechanisms

OBJECTIVE

To review our current understanding of immunotherapy, the immune mechanisms underlying food allergy, and the methodological advances that are furthering our understanding of the role of immune cells and other molecules in mediating food allergies.

DATA SOURCES

Literature searches were performed using the following combination of terms: allergy, immunotherapy, food, and mechanisms. Data from randomized clinical studies using state-of-the-art mechanistic tools were prioritized.

STUDY SELECTIONS

Articles were selected based on their relevance to food allergy.

RESULTS

Current standard of care for food allergies is avoidance of allergenic foods and the use of epinephrine in case of severe reaction during unintentional ingestion. During the last few decades, great strides have been made in understanding the cellular and molecular mechanisms underlying food allergy, and this information is spearheading the development of exciting new treatments.

CONCLUSION

Immunotherapy protocols are effective in desensitizing individuals to specific allergens; however, recurrence of allergic sensitization is common after discontinuation of therapy. Interestingly, in a subset of individuals, immunotherapy is protective against allergens even after discontinuation of immunotherapy. Whether this protection is permanent is currently unknown because of inadequate long-term follow-up data. Research on understanding the underlying mechanisms may assist in modifying protocols to improve outcome and enable sustained unresponsiveness, rather than a temporary relief against food allergies. The cellular changes brought about by immunotherapy are still a black box, but major strides in our understanding are being made at an exciting pace.

Beyond Hygiene: Commensal Microbiota and Allergic Diseases

Complex communities of microorganisms, termed commensal microbiota, inhabit mucosal surfaces and profoundly influence host physiology as well as occurrence of allergic diseases. Perturbing factors such as the mode of delivery, dietary fibers and antibiotics can influence allergic diseases by altering commensal microbiota in affected tissues as well as in intestine. Here, we review current findings on the relationship between commensal microbiota and allergic diseases, and discuss the underlying mechanisms that contribute to the regulation of allergic responses by commensal microbiota.

The role of immune mechanisms in alcoholic and nonalcoholic steatohepatitis: a 2015 update

So far, innate immune mechanisms have been recognized as the main responsible for the evolution of both alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH). However, increasing evidence points toward the possible role of adaptive immune responses, as an additional factor in promoting hepatic inflammation in steatohepatitis. In this article, we discuss recent data involving circulating antibodies and lymphocyte-mediated responses in sustaining the progression of ASH and NASH to fibrosis, as well as the possible mechanisms implicated in favoring the onset of adaptive immunity in the setting of steatohepatitis.