Found in every tissue in the body, macrophages are large immune cells known for their ability to engulf and destroy pathogens, yet they also perform many other duties. In the testes, they are involved in both its key functions, the production of sperm and testosterone. Pictured in a mouse testis, macrophages (in turquoise) surround the seminiferous tubules (in red), where sperm are made. As sperm are only produced after puberty, other immune system cells may see them as ‘foreign’ tissue so testicular macrophages also secrete defensive proteins to protect them. Two types of macrophages, with different developmental pathways, fulfil these crucial roles. Those found alongside testosterone-producing Leydig cells in the interstitial spaces of the testes originate from precursors in the embryo, while macrophages around the seminiferous tubules develop at puberty, from bone marrow cells. A deeper understanding of both types of macrophages could prove relevant to studies of male fertility.
Written by Emmanuelle Briolat
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