SFTPB and cystic fibrosis: All of the 5 studied SFTPA1 SNPs are associated with CF through 13 intergenic SNP-SNP interactions with SNPs in SFTPA2 (n = 2), SFTPB (n = 3), and SFTPC (n = 8) (X2 is 2.2285–7.8947, p = 0.0487–0.0007) (Table 4, Figure 1A).