Our studies aim to elucidate the role of T regulatory (Treg) cells in peripheral immunological tolerance. We are particularly interested in identifying novel genetic pathways that control Treg cell function and are targeted by mutations in human diseases. We are also interested in elucidating mechanisms by which of Treg cells maintain mucosal tolerance and how their breakdown fosters inflammatory diseases, particularly food allergy and asthma.
Our studies on mechanisms by which Treg cells maintain mucosal tolerance led to the identification of Treg cells as microbial sensors that respond to microbiota signals delivered via the Toll-like receptor-coupled adaptor MyD88 to regulate the interaction of the adaptive immune response with the commensal flora (1). Dysfunction of the latter pathway maybe relevant to several disorders of intestinal mucosal inflammation such as seen in Treg cell deficiency diseases (2).
We have extended our studies on Treg cells in mucosal tolerance to common allergic disorders including food allergy and asthma, which is characterized by the breakdown in tolerance to normally innocuous nutrients. Our studies on the causes of tolerance breakdown in food allergy and allergic airway inflammation have identified Treg cells as the target of subversion by disease pathways, which render the Treg cells pro-inflammatory (3-5). Reprogramming the Treg cells by antagonizing pro-allergic cytokines and pathways offers promising therapeutic strategies for re-establishing oral tolerance in subjects with food allergies and asthma. We are currently pursuing proof of concept studies using preclinical mouse models that we have developed in our laboratory. We aim to translate these studies into clinical trials in the near future.
Our studies on the fundamental biology of Treg cells have led to the recent elucidation of the role of inflammatory signals delivered via the Notch receptor pathway in disrupting Treg cell function (6). Intense, aberrant activation of Notch signaling in Treg cells in graft versus host disease plays a prominent role in the immunopathology of this disorder. Notch signaling in Treg cells is also highly relevant to mechanisms by which environmental pollutants such as particulate matter (PM) generated by combustion engines promote airway inflammation. We have shown that PM activates a signaling pathway involving the Aryl hydrocarbon receptor and the Notch ligand jagged 1 to augment allergic airway inflammation (7). Blockade of Notch receptor signaling in Treg cells may offer therapeutic potential in these and other inflammatory and autoimmune diseases.
Finally, we have complemented our investigations on the role of Treg cells in peripheral tolerance in genetic animal models and common inflammatory disorders with studies that focus on gene discovery in human subjects with heritable immune dysregulatory diseases and Treg cell deficiency. Our previous studies have identified FOXP3, IL2RA and DOCK8 as targets of mutations in human subjects that cause distinct autoimmune and immunodysregulatory disorders in affected human subjects. Our latest studies have extended these genetic networks to include LRBA, encoding LPS-responsive Beige-like Anchor protein, as a cause of Treg cell deficiency and autoimmunity in human subjects (8). The mechanisms by which mutations affecting these genes disrupt tolerance remains the subject of ongoing investigations by our group.