Used in immunological research to quantify levels of surfactant protein D (SP-D) in biological samples such as bronchoalveolar lavage fluid, serum, or plasma. SP-D is a biomarker for lung health and plays a role in innate immune defense in the respiratory tract. The ELISA kit enables researchers to study lung inflammation, infection, and diseases like COPD, asthma, cystic fibrosis, and acute respiratory distress syndrome (ARDS). It is also used in studies assessing pulmonary response to environmental pollutants, smoking, or viral infections including influenza and SARS-CoV-2. The assay supports both clinical research and drug development by providing a reliable measure of lung epithelial injury and immune modulation.