Intra-testicular transplants are placed in rodents into the large lymphatic sinusoids of the interstitial tissue of the testis. These sinusoids are filled with a protein-rich extracellular fluid that supplies all the requirements of the grafts until vascularization takes place. The testicular microvascular endothelium regulates transport of T lymphocytes and immunoglobulin G to the testis and may thus contribute to regulation of the immune system in this organ. Differences in the organization of the lymphatic drainage exist between species, but in every studied species lymphatic drainage from the testis leads to lymph nodes.