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At puberty, neighboring SC develop tight junctions, forming an impermeable blood–testes barrier [40]. The barrier is a modified occluding junction located in the basal third of the seminiferous epithelium [43]. The blood–testes barrier divides the seminiferous epithelium into basal and adluminal compartments [44]. The basal part houses spermatogonia, preleptotene, and leptotene spermatocytes, while further advanced meiotic spermatocytes and spermatids reside in the adluminal part [34].

The blood–testes barrier shields germ cells in the adluminal part of the ST from direct contact with blood, protecting the cells from toxic, mutagenic, and autoimmune reactions. The barrier maintains specific concentrations of androgen‐binding protein, inhibin, activin, and enzyme inhibitors within the adluminal compartment of the ST. It controls transport of molecules and wastes to and from the adluminal compartment [45, 46]. The blood–testis barrier also functions as an immunological barrier to protect novel proteins at spermatocytes and spermatids from autoimmune reaction and inhibits immunoglobulins and lymphocytes from entering the adluminal part [35]. SC and germ cells produce interferons, interferon‐induced proteins, interleukins, and cytokines, which maintain an antiviral defense system [47].