Because its main function is to nourish the developing sperm cells through the stages of spermatogenesis, the<unk>  has also been called the "mother" or "nurse" cell.<unk> s also act as phagocytes, consuming the residual cytoplasm during spermatogenesis. Translocation of cells from the base to the lumen of the seminiferous tubules occurs by conformational changes in the lateral margins of the<unk> s. Secretory<unk> s secrete the following substances: * anti-Müllerian hormone (AMH) — secreted during the early stages of fetal life. * inhibin and activins — secreted after puberty, and work together to regulate FSH secretion. * androgen binding protein (also called testosterone binding globulin) — increases testosterone concentration in the seminiferous tubules to lightly stimulate spermatogenesis. * estradiol — aromatase from<unk> s convert testosterone to 17 beta estradiol to direct spermatogenesis * ETS Related Molecule or ERM transcription factor ERM transcription factor — needed for maintenance of the spermatogonial stem cell in the adult testis. * transferrin — a blood plasma protein for iron ion delivery * Testicular ceruloplasmin — a ceruloplasmin-like protein which is immunologically similar to serum ceruloplasmin Structural The occluding junctions of<unk> s form the blood-testis barrier, a structure that partitions the interstitial blood compartment of the testis from the adluminal compartment of the seminiferous tubules. Because of the apical progression of the spermatogonia (sperm stem cells), the occluding junctions must be dynamically reformed and broken to allow the immunoidentical spermatogonia to cross through the blood-testis barrier so they can become immunologically unique.<unk> s control the entry and exit of nutrients, hormones and other chemicals into the tubules of the testis as well as make the adluminal compartment an immune-privileged site. The cell is also responsible for establishing and maintaining the spermatogonial stem cell niche, which ensures the renewal of stem cells and the differentiation of spermatogonia into mature germ that progress stepwise through the long process of spermatogenesis, ending in the release of spermatozoa in a process known as spermiation.<unk> s bind to spermatogonial cells via N-cadherins and galactosyltransferase (via carbohydrate residues). Other functions During the maturation phase of spermiogenesis, the<unk> s consume the unneeded portions of the spermatozoa. DNA repair and mutation<unk> s are capable of repairing DNA damage. This repair likely employs the process of non-homologous end joining involving XRCC1 and PARP1 proteins that are expressed in<unk> s.<unk> s have a higher mutation frequency than spermatogenic cells. Compared to spermatocytes, the mutation frequency is about 5 to 10-fold higher in<unk> s. This may reflect the need for greater efficiency of DNA repair and mutation avoidance in the germ line than in somatic cells. Immunomodulatory properties of<unk> s Besides expressing factors that are crucial for sperm cell maturation,<unk> s are producing a wide range of molecules (either on their surface or soluble) that are able to modify the Immune system (IS). The ability of<unk> s to change the immune response in the tubule is needed for successful sperm cell maturation. Sperm cells are expressing neoepitopes on their surface as they progress through different stages of maturation. They can trigger a strong immune response if placed in a different site of the body. Molecules produced by<unk> s associated with immunosuppression or immunoregulation FAS/FAS-L system – expression of Fas ligand (Fas-L) on the surface of<unk> s activates apoptotic death of Fas receptor bearing cells, f.e. cytotoxic T-cells. - soluble FasL- increasing the effectivity of the system - soluble Fas- FasL blockage on the surface of other cells ( no apoptotic induction in<unk> s by cells of IS) B7/H1 – decreasing proliferation of effector T-cells Jagged1 (JAG1) – induction of Foxp3 transcription factor expression in naive T lymphocytes (increasing relative numbers of T regulatory cells) Protease inhibitor-9 (PI-9) – member of serpin family (serine protease inhibitors) - induces secretion of protease Granyzme B, cytotoxic T-cells and NK cells are able to induce apoptosis in target cell.<unk> s produce PI-9 that irreversibly bonds Granzyme B and inhibits its activity CD59 - surface molecule on<unk> s, member of the Complement Regulatory Proteins (CRP) - inhibits the last step of complement cascade – formation of the Membrane Atack Complex Clusterin – a soluble molecule, function similar to CD59 – making complex with Granyzme B and inhibits activation of apoptosis by T-lymphocytes or NK cells TGF-beta – transforming growth factor beta (its direct production by<unk> s is controversial) - induction of regulatory T-cells in periphery Another molecules involved CD40 - molecule associated with Dendritic Cells (DC) -<unk> s are able to down regulate the expression of CD40 on the surface of DCs (mechanism not known) - Downregulation of CD40 results in decreased ability of DCs to stimulate the T-cell response<unk> s are also able to inhibit the migration of immune cells – lower immune cells infiltration to the site of inflammation.
Sertoli cell
Elliptocyte
Krause's glands
LE cell
Nurse cell
Ciaccio's glands
Skene's gland
Serous gland