Role of macrophages in testis function.

The testis is a unique organ that simultaneously supports spermatogenesis and steroidogenesis, and it must maintain host defense against infection while suppressing excessive immune responses in an environment that includes germ cell antigens that emerge after sexual maturation. Testicular macrophages reside in the testicular interstitium starting in fetal life and localize near Leydig cells and around seminiferous tubules. Through cytokine and lipid mediator production, phagocytosis of dying cells, and antigen presentation, testicular macrophages can influence both steroidogenesis and spermatogenesis. In this chapter, we summarize the key components underlying testicular immune privilege, including the blood-testis barrier (BTB), immunosuppressive factors, and immune cell constituents in the testis, and we provide an overview of the development and maintenance of testicular macrophages and their interactions with major testicular cell types such as Leydig cells. We also outline changes that occur during inflammation and summarize links between testicular macrophages and disease states, including infertility and aging. Finally, we discuss future research directions and potential intervention strategies focused on testicular macrophages.