SFTPA1 and infection: Although there are only a few amino acid differences between SP-A1 and SP-A2 variants, SP-A2 variants have a higher capacity to bind carbohydrates, enhance phagocytosis of invading pathogens by macrophages and induce higher proinflammatory cytokine production in immune cells under various stressed conditions, indicative of the potential of SP-A variants to differentially regulate immune function in the context of infection (21–24).