Deletion of the VDR has been shown to disrupt TJs in the lungs, leading to impaired barrier function and increased susceptibility to inflammatory damage, thereby implicating VDR signaling as a key determinant of pulmonary epithelial integrity in conditions such as pneumonia, asthma, and chronic obstructive pulmonary disease (COPD) [242]. Here, VDR is linked to susceptibility to pneumonia measurement.