SFTPA2 and hypersensitivity pneumonitis: Out of the 16 interactions associated with increased HP risk, 7 were among SNPs of the hydrophilic SPs (SFTPA1, SFTPA2, and SFTPD) alone, the rest (n = 9) were among SNPs of both the hydrophilic and hydrophobic (SFTPB and SFTPC) SPs.