Questionable thymic nurse cell

Since their discovery in 1980, thymic nurse cells (TNCs) have been controve rsial. Questions pertaining to the existence of the TNC as a "unit" cell wi th thymocytes completely enclosed within its cytoplasm were the focus of in itial debates. Early skeptics proposed the multicellular complex to be an a rtifact of the procedures used to isolate TNCs from the thymus. Since that time, TNCs have been found in fish, frogs, tadpoles, chickens, sheep, pigs, rats, mice, and humans. Their evolutionary conservation throughout the ani mal kingdom relieved most speculations about the existence of TNCs and at t he same time demonstrated their apparent importance to the thymus and T-cel l development. In this review we will discuss and debate reports that descr ibe (i) the organization or structure of TNCs, (ii) the thymocyte subset(s) found within the cytoplasm of TNCs and their uptake and release, and (iii) the junction of this fascinating multicellular interaction that occurs dur ing the process of T-cell development. Discussions about the future of the field and experimental approaches that will lead to answers to remaining qu estions are also presented.