There are hypersensitivity responses, both a type I response (atopic, with formation of immunoglobulin E, or IgE) and a type III hypersensitivity response (with formation of immunoglobulin G, or IgG). The reaction of IgE with "Aspergillus" antigens results in mast cell degranulation with bronchoconstriction and increased capillary permeability. Immune complexes (a type III reaction) and inflammatory cells are deposited within the mucous membranes of the airways, leading to necrosis (tissue death) and eosinophilic infiltration. Type 2 T helper cells appear to play an important role in ABPA due to an increased sensitivity to interleukin (IL) 4 and IL-5. These cytokines up-regulate mast cell degranulation, exacerbating respiratory decline.