Pigeon breeders can develop hypersensitivity pneumonitis. What is the mechanism of this disease?

Hypersensitivity pneumonitis, often seen in pigeon breeders and those exposed to organic dust, is primarily caused by an IgG-mediated immune response. In this condition, repeated exposure to specific antigens found in organic materials, including proteins from bird droppings, leads to the formation of IgG antibodies.

These IgG antibodies react with the inhaled antigens, forming immune complexes which can initiate an inflammatory response. This response involves the activation of various immune cells and can lead to lung inflammation and damage. Over time, chronic exposure to the offending antigens may result in progressive lung disease, as the inflammatory process continues.

In contrast, an IgE-mediated response is typically associated with immediate hypersensitivity reactions, such as those seen in allergic conditions like asthma or allergic rhinitis. Cell-mediated responses refer to processes primarily involving T lymphocytes, which might contribute to chronic inflammation but are not the primary mechanism in hypersensitivity pneumonitis. Lastly, complement-mediated responses involve the complement system but do not characterize the primary mechanism driving hypersensitivity pneumonitis.

The emphasis on IgG as the key player aligns with the pathophysiology observed in individuals with conditions like hypersensitivity pneumonitis, highlighting its role in chronic inflammatory responses related to antigen