SFTPD and COVID-19: Surfactant is mainly produced in the lung, but surfactant mRNA and protein have also been identified in heart, arteries, kidney, and other organs (56, 86, 92) (Figures 3, 4); and SP-A and SP-D seem to modulate the immune response by preventing excessive inflammation, as found in the cytokine storm caused by COVID-19, that can potentially damage the lungs and impair gas exchange (55).