Blood-testis barrier

The blood-testis barrier (abbreviated as BTB) is a physical barrier between the blood vessels and the seminiferous tubules of the animal testes.

The barrier is formed by tight connections between the Sertoli cells, which are sustentacular cells (supporting cells) of the seminiferous tubules, and nourish the spermatogonia.

The barrier avoids passage of cytotoxic agents (bodies or substances that are toxic to cells) into the seminiferous tubules.

Autoimmune response
The blood-testes barrier can be damaged by trauma to the testes (including torsion or impact), by surgery or as a result of vasectomy. When the blood-testes barrier is breached, and sperm enters the bloodstream, the immune system mounts an autoimmune response against the sperm. The anti-sperm antibodies generated by the immune system can bind to various antigenic sites on the surface of the sperm. If they bind to the head, the sperm may be less able to fertilize an egg, and if they bind to the tail, the motility of the sperm can be reduced.