Which type of cell forms the blood-testis barrier crucial for immune protection of developing spermatozoa?

Sertoli cells are responsible for forming the blood-testis barrier, which plays a vital role in protecting developing spermatozoa from the immune system. These cells are located within the seminiferous tubules of the testes and provide support and nourishment to germ cells during spermatogenesis.

The blood-testis barrier consists of tight junctions between adjacent Sertoli cells, creating a segregated environment that prevents the passage of harmful substances and immune cells from the bloodstream into the lumen of the seminiferous tubules. This barrier is essential because spermatozoa are haploid cells, which means they have half the number of chromosomes compared to somatic cells, making them potentially recognizable as foreign by the immune system. The barrier not only protects the developing sperm but also regulates the microenvironment crucial for their maturation.

Leydig cells, while important for producing testosterone, do not contribute to the formation of the blood-testis barrier. Primary and secondary spermatocytes are stages in the process of spermatogenesis but do not have a direct role in creating or maintaining the barrier that protects sperm development. Thus, Sertoli cells are the key component in preserving the integrity of the environment necessary for sperm development and immune protection.