This work demonstrated that B cells, which typically protect us against infection, function abnormally and promote interstitial lung disease in patients with common variable immunodeficiency (CVID). CVID is a primary immunodeficiency, a type of disorder where individuals have an immune system that does not function properly – causing infections and, for reasons not understood, also leading to “non-infectious” complications like interstitial lung disease. Dr. Maglione and colleagues were able to therapeutically target B cells and ameliorate the lung disease in all 11 patients they treated. Using this approach, they were able to spare the patients side effects of more broadly immunosuppressive therapies. Lastly, they were able to determine that a protein known as B cell activating factor, or BAFF, is an important driver of the dysregulated B cells that drive this lung disease through a specific interaction BAFF has with BAFF receptor. This disease pathway mediated by BAFF may be a useful target for therapeutic interventions in these patients.