DEFA1（defensin alpha 1），癌症关联基因，基因ID：1667，防御素是一个抗菌和细胞毒性肽家族，被认为与宿主防御有关。大量存在于中性粒细胞颗粒中，也存在于肠、呼吸道、尿路和阴道等粘膜表面的上皮细胞中。防御素家族成员在蛋白质序列上高度相似，以保守的半胱氨酸基序为特征。该基因编码的蛋白防御素α1存在于中性粒细胞的杀微生物颗粒中，可能在吞噬细胞介导的宿主防御中起作用。一些α防御素基因聚集在8号染色体上。这个基因与防御素α3只有一个氨基酸不同。这个基因和编码防御素α3的基因都受到拷贝数变异的影响。Defensins are a family of antimicrobial and cytotoxic peptides thought to be involved in host defense. They are abundant in the granules of neutrophils and also found in the epithelia of mucosal surfaces such as those of the intestine， respiratory tract， urinary tract， and vagina. Members of the defensin family are highly similar in protein sequence and distinguished by a conserved cysteine motif. The protein encoded by this gene， defensin， alpha 1， is found in the microbicidal granules of neutrophils and likely plays a role in phagocyte-mediated host defense. Several alpha defensin genes are clustered on chromosome 8. This gene differs from defensin， alpha 3 by only one amino acid. 。