SFTPA2 and viral infectious disease: Animal models of SP-C and collectin deficiencies show a significant defect in host defence since: (i) SP-C, SP-A, and SP-D knock-out mice are more susceptible to bacterial, fungal, and viral infections [157,232,233,234,235], (ii) SP-A−/− and SP-D−/− mice show reduced uptake of these microbes by alveolar macrophages (reviewed in [236]), and (iii) bacterial clearance is restored by intratracheal administration of SP-A [237].