睾丸免疫豁免与天然免疫

Abstract

Orchitis is one of the etiological factors of male infertility. The testis is a remarkable immune privileged organ and represents a special immunological environment. Immune privilege implies a small number of tissues in the body where allo- and auto-antigens are tolerated to prevent tissue damage and dysfunction by the systemic immune response. Immune privileged sites in mammals include the testis, brain, eyes and pregnant uterus. The two main functions of the testis are sperm production and androgen synthesis. Since the production of mature sperm occurs exclusively post-puberty, long after immune competence is established during fetal and early neonatal life, a large number of auto-antigens synthesized by germ cells are immunogenic. However, these germ cell auto-antigens do not induce immune responses within the testis, because of "immune privilege". Testicular immune privilege status is maintained by a combination of physical structures, testicular cell properties and local immune suppressive molecules. However, the testis can be infected by invading microbial pathogens. To overcome immune privilege and mount an appropriate local immune response to protect the testis from infection, tissue-specific cells have adopted effective innate immune functions against invading pathogens. Balance of the testicular immunological environment is necessary for tissue functions. Breakdown of immune homeostasis in the testis may lead to chronic orchitis, a significant etiological factor for male infertility. The mechanisms underlying testicular immune privilege and innate immunity are important issues in the field of reproductive biology. This review highlights the progress of studies on these issues, and outlines topics that are worthy of further investigation.