Surfactant/SP-D [MD165R]

Pulmonary surfactant is primarily responsible for lowering the surface tension at the air-liquid interface in the alveoli, a process that is essential for normal respiration. Pulmonary surfactant is a mixture of phospholipids and proteins, including four distinct surfactant-associated proteins (SPs): SP-A, SP-B, SP-C, and SP-D. SP-B and SP-C showed strong immunohistochemical expression in Lung Hyperplasias and Adenomas, suggesting that SP-B and SP-C are related to lung tumorigenesis. SP-A and SP-D are large multimeric proteins belonging to the family of calcium-dependent lectins, designated Collectins, which contribute to the innate immune system. SP-D is a protein encoded by the SFTPD gene. Studies found low expression of SF-D expression in lung, gastric, and breast cancers and high expression in different stages and grades of ovarian cancer. SF-D expression could be associated with a favorable prognosis in lung cancer but unfavorable in non-pulmonary sites such as breast, gastric and ovarian cancers. The purified Spike protein of SARS-CoV-2 bound to Vero but not 293T cells and was itself recognized by SP-D, in the lung alveoli. It suggests that SARS-CoV interacts with innate immune mechanisms in the lung through its S-protein and regulates pulmonary inflammation.