Report from the National Institute of Allergy and Infectious Diseases workshop on "Atopic dermatitis and the atopic march: Mechanisms and interventions".

Atopic dermatitis (AD) affects up to 20% of children worldwide and is an increasing public health problem, particularly in developed countries. Although AD in infants and young children can resolve, there is a well-recognized increased risk of sequential progression from AD to other atopic diseases, including food allergy (FA), allergic rhinitis, allergic asthma, and allergic rhinoconjunctivitis, a process referred to as the atopic march. The mechanisms underlying the development of AD and subsequent progression to other atopic comorbidities, particularly FA, are incompletely understood and the subject of intense investigation. Other major research objectives are the development of effective strategies to prevent AD and FA, as well as therapeutic interventions to inhibit the atopic march. In 2017, the Division of Allergy, Immunology, and Transplantation of the National Institute of Allergy and Infectious Diseases sponsored a workshop to discuss current understanding and important advances in these research areas and to identify gaps in knowledge and future research directions. International and national experts in the field were joined by representatives from several National Institutes of Health institutes. Summaries of workshop presentations, key conclusions, and recommendations are presented herein.

TIM-4 expressed by mucosal dendritic cells plays a critical role in food antigen-specific Th2 differentiation and intestinal allergy.

BACKGROUND & AIMS: Food allergy accounts for significant morbidity. The etiology and immune mechanisms of food allergy, however, have remained poorly understood. In this study, we aimed to determine the role of T-cell immunoglobulin-domain and mucin-domain (TIM)-4, a recently identified member of cell surface molecules, in the pathogenesis of intestinal allergy in a murine model. METHODS: We report that TIM-4 as well as costimulatory molecules were up-regulated in intestinal mucosal dendritic cells by in vitro or in vivo exposure to Staphylococcus enterotoxin B (SEB). SEB-conditioned intestinal dendritic cells loaded with a food macromolecule ovalbumin (OVA) induced potent OVA-specific T-helper (Th)2 lymphocyte responses in vitro and such Th2 responses were inhibited completely by TIM-4 blockade. RESULTS: In vivo exposure to both SEB and OVA resulted in OVA-specific Th2 differentiation and intestinal allergic responses including increased serum immunoglobulin E and Th2 cytokine levels, activation of OVA-specific Th2 cells detected both ex vivo and in situ, and mast cell degranulation. Of importance, in vivo abrogation of TIM-4 or its cognate ligand TIM-1 by using a polyclonal antibody remarkably dampened Th2 differentiation and intestinal allergy. CONCLUSIONS: Our study thus identifies TIM-4 as a novel molecule critically required for the development of intestinal allergy.