Beta-Defensin 2 & 3 贝塔-防御素-2和3

防御素是一族15到20个氨基酸残基组成含有三或四条二硫键结构的阳离子蛋白质。脊椎类或非脊椎类动物都有防御素， 它主要分布于机体的免疫系统， 如颗粒性白细胞、上皮细胞等。他们的功能主要是抵抗或防御细菌、真菌或病毒的侵犯。防御素因为其蛋白质分子具有阳电荷等特性，可以吸附和粘附细菌的细胞壁， 并形成细菌细胞膜的微孔， 导致细菌细胞内容物外流。贝塔-防御素-2和贝塔-防御素-3是两种反映炎症反映的生物标示物。
Defensins are cationic, anti-microbial peptides, produced by many cell types (e.g., leukocytes, epithelium, dendrites), and which play prominent roles in the innate immune response of mammals. Two classes have been described in humans, the alpha- and beta-defensins, which range from 3.5 to 4.5 kDa and are stabilized by three intramolecular disulfide bonds differing by the ordering of the disulfide bonds in the mature peptides. To date, six alpha-defensins (also referred to as Human Neutrophil Peptides, HNP1-6) and six beta-defensins (HBD1-6) have been investigated. All have demonstrated broad-spectrum in vitro antimicrobial activity against bacteria, fungi and enveloped viruses – activities that are expected to be significant for in vivo protection against pathogens. Researchers have also investigated the ability of defensins to induce the release from tissues of cytokines and chemokines involved in inflammatory and/or adaptive immunity, thereby providing a regulatory role that bridges innate and adaptive immunity. Investigative research has led to the measurement of defensins in serum, saliva, milk, amniotic fluid and lung and cervicovaginal lavage, and culture media of cells and tissue of blood, lung, skin, bowel, muscle, cartilage and kidney, among other sample types.