衣原体中普遍含有一个7.5 kb左右的隐蔽性质粒，在衣原体物种中高度保守。Pgp3为该质粒编码的相对分子质量约28 000的免疫原性蛋白，能分泌到宿主细胞胞质中。在衣原体感染期间人类抗体可识别Pgp3的天然三聚体结构。Pgp3在衣原体致病机制中起重要作用，是诱导输卵管积液的主要毒力因子，能中和抗菌肽LL37的抗衣原体活性，且其DNA疫苗对衣原体感染具有一定的保护作用。本文就Pgp3的结构、在衣原体致病中的作用及其在疫苗与诊断抗原方面的应用进行简要概述，为进一步研究衣原体感染的发病机制及其诊断与预防提供新的思路。

Pgp3 is one of the products produced by a small (about 7.5 kb) but highly conserved cryptic plasmid contained in some chlamydiae. This protein is secreted into the cytoplasm of the host cells and known as a virulence factor associated with hydrosalpinx. Its native conformation is a triplex that can be recognized by host immune system. Pgp3 can neutralize the antichlamydial activity of human cathelicidin LL37. This review presents current research progress on the structure, pathogenesis and applications of Pgp3, and provides the new sights in chlamydial pathogenesis and vaccine preparation.