Blood-testis barrier

Blood-testis barrier (BTB) is a physical barrier between the blood vessels and the seminiferous tubules of the testis. This barrier is formed by tight junctions, adherens junctions and gap junctions between the Sertoli cells, which are located in the seminiferous tubule. The main function of the BTB is to protect the developing sperm from harmful substances and immune responses.

Structure

The BTB is one of the tightest barriers in the mammalian body. It is formed by Sertoli cells, which are connected by tight junctions, adherens junctions and gap junctions. These junctions prevent the passage of most molecules from the blood into the seminiferous tubules. The BTB divides the seminiferous tubule into a basal compartment, which is accessible to blood-borne substances, and an adluminal compartment, which is not.

Function

The main function of the BTB is to protect the developing sperm from harmful substances and immune responses. The BTB prevents molecules larger than 800 Da from passing through, and is impermeable to water-soluble and charged molecules. This allows the testis to control the microenvironment in which the sperm develop, protecting them from harmful substances in the blood.

The BTB also prevents autoimmune responses against the developing sperm. Sperm begin to develop at puberty, after immune tolerance is established, and therefore could potentially be recognized as foreign by the immune system. The BTB prevents immune cells from accessing the sperm, protecting them from immune attack.

Clinical significance

Disruption of the BTB can lead to infertility. This can occur as a result of genetic mutations, exposure to toxic substances, or injury. In addition, some infections can disrupt the BTB, allowing immune cells to access the sperm and potentially causing autoimmune orchitis.

See also

• Sertoli cell
• Seminiferous tubule
• Testis
• Blood-brain barrier