Intrathymic events in the differentiation of T lymphocytes: a continuing enigma.

The thymus plays an important role in the differentiation of T lymphocytes, but the exact nature of this role remains unclear. As Roland Scollay shows here, a careful analysis of available data shows how poorly we understand the role of the thymic cortex and medulla and how little we know of the exact processes which give rise to thymus-dependent peripheral T cells.