Immune type cells influence commitment of OSC. Staining of the adult human OSC (osc), tunica albuginea (ta), and an adjacent cortex (ct) for CD14 of primitive MDC and HLA-DR of activated MDC, CD8 of cytotoxic/suppressor T cells, MHC class I heavy chain, and Thy-1 glycoprotein of pericytes, as indicated in panels. Large asterisks and dashed lines indicate putative germ cells. A) Primitive MDC associate with OSC (arrows) and accompany (arrowheads) origination of germ cells by asymmetric division of OSC (asterisks). B) Asymmetric division is also accompanied by extensions from T cell (arrowheads) into a putative germ cell daughter. C) Primitive MDC accompany (white arrowheads) symmetric division (s-s') of germ cells in tunica albuginea and their migration into the adjacent cortex (ct). D) Migrating tadpole-like germ cells are accompanied by activated MDC (open arrow), and HLA-DR material is apparent in the cytoplasm (solid arrow) and in the nuclear envelope (arrowhead). E) The germ cells associate with cortical vasculature (cv) strongly expressing MHC-I (arrows vs. arrowhead), enter and are transported by the bloodstream (F). Adapted from , with permission, © Blackwell Publishing, Oxford, UK.