The research outlined in the proposal aims to elucidate a fundamental pathway regulating dendritic cell induction of T cell sensitization to allergens in the lung. Work over the past 15 years has determined that mature pulmonary dendritic cells (DC) from the lung regulate type 2 CD4+ T cell (Th2) responses to allergens in asthma and that activation of pattern recognition receptors such as Toll-like receptors (TLRs) is a primary determinant of DC maturation driving sensitization. Although the early steps of TLR-induced DC maturation and the later steps of chemokine guided migration to draining lymph nodes are well characterized, relatively little is known about the intermediate step of DC detachment from inflamed tissues. We recently discovered a new innate immune pathway within the DC that specifically regulates its ability to egress from inflamed tissues while leaving the ret of the inflammatory and antigen presenting functions intact. NLRP10 is a member of the NOD-like receptor class of pattern recognition receptors and in its absence, DCs fail to traffic antige to lymph nodes and consequently CD4+ T cell priming is profoundly impaired. We will delineate how NLRP10 regulates dendritic cell movement, in exactly which type of DC and what aspects of lung immunity are impaired in the absence of NLRP10 through the following two specific aims.
Aim 1) Identify NLRP10-dependent and - independent dendritic cell subsets in the lung and define their ability to activate CD4+ and CD8+ T cells. Preliminary data suggests that loss of NLRP10 only affects a subset of DCs (expressing the marker CD11b), which preferentially prime CD4+ but not CD8+ T cells. We hypothesize that paralysis of NLRP10-dependent DCs in the lung will result in tolerance rather than Th2 priming following aeroallergen exposure while leaving NLRP10-independndent DC priming of anti-viral CD8+ T cells intact. We will test this hypothesis in Aim 1 using in vivo aeroallergen sensitization models (Th2) and influenza infection (CD8+ T cell). NLRP10-deficient mice provide the only animal model in which the function of the migratory CD11b+ DC subset is specifically affected and therefore allows for the first time determination of the exact role of these DCs in pulmonary immune responses.
Aim 2) Determine whether failed DC trafficking to lymph nodes is due to impaired DC detachment from lung extracellular matrix molecules. To define the molecular interactions regulating DC release from the lung we will develop matrices with recombinant matrix molecules to test NLRP10-deficient DC adhesion and migration in vitro;further we will block primary determinants of DC attachment to the lung parenchyma in vivo to overcome failed Th2 priming to aeroallergens in NLRP10-deficient mice. If loss of NLRP10 selectively abrogates DC-mediated CD4+ T cell priming to aeroallergens, then targeting this pathway might allow us to control the balance between sensitization and tolerance in allergic disease while potentially leaving protective CD8+ T cell immunity intact. Therefore our long-term goal following completion of these studies is to develop a DC-based approach to treat allergic disease through inhibition of NLRP10 pathways.
We have known for more than 20 years that asthma and other allergic diseases are driven by a mistargeted type 2 helper T cell (Th2) response to ''innocuous'' environmental triggers such as pollens and animal danders; yet an immunologic intervention to block or reverse activation of these Th2 cells remains an unmet goal. As dendritic cells are the primary determinant of whether T cells become activated rather than tolerized to allergens; targeting this cell type represents a likely yet unexplored approach to halt allergen sensitization in asthmatics. A recently identified molecule in dendritic cells; NLRP10; regulates whether mature dendritic cells carry antigen to draining lymph nodes where na ve T cells await activation and therefore defining the molecular defect in NLRP10-deficient dendritic cells and how modulation of these cells in the lung affects T cell activation will lay the groundwork for accomplishing this goal.