Blood–testis barrier

A selective barrier formed mainly by tight junctions between Sertoli cells in the seminiferous tubules. It separates developing germ cells from blood-borne substances and helps maintain their specialized environment.

Sertoli cell: A supporting cell in seminiferous tubules that nourishes developing germ cells and regulates their environment. Adjacent Sertoli cells form the junctions that create this barrier.
Seminiferous tubule: A coiled tube in the testis where sperm are produced. Sertoli-cell barriers divide the interior of these tubes into distinct environments.
Immune privilege: The relative protection of certain tissues from immune responses that would occur elsewhere in the body. The barrier limits immune exposure to germ-cell antigens that appear after immune tolerance develops.
Sertoli cell–germ cell signaling: Communication between Sertoli cells and developing germ cells through direct contact and signaling molecules. These signals help coordinate junction remodeling with germ-cell movement.
Tight junction: A cell-to-cell junction that seals gaps between neighboring cells and restricts movement through the space between them. Tight junctions between Sertoli cells provide the barrier’s principal structural seal.
Spermatogonium: A diploid germ cell near the outer wall of a seminiferous tubule that can give rise to sperm. Spermatogonia occupy the basal compartment, outside the barrier’s adluminal compartment.
Autoimmune orchitis: Inflammation of the testes caused by an immune response against testicular tissues. Barrier disruption can expose germ-cell antigens and contribute to testicular autoimmunity.
Blood–testis barrier permeability: The degree to which substances can cross the blood–testis barrier under particular conditions. Permeability varies with the substance and physiological or pathological state.
Adherens junction: A cell-to-cell junction that connects neighboring cells through adhesion proteins linked to the cytoskeleton. Adherens junctions help organize Sertoli-cell contacts alongside the barrier’s tight junctions.
Spermatocyte: A germ cell that undergoes meiosis during sperm development. Developing spermatocytes cross Sertoli-cell junctions as they enter the adluminal compartment.

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