Recently identified measures of human thymic function

The increase in the number of patients with iatrogenic and disease-induced T-cell depletion over the last generation has heightened the sense of urgency for improved diagnostic modalities for immune reconstitution. A full understanding of immune reconstitution requires quantification of every important immune cell population. A cell population that is essential for full reconstitution of a robust immune system is the naive T cells that have recently emigrated from the thymus, the so-called recent thymic emigrants. In this article, we review the emerging methodologies, rationale and indications for monitoring human thymus function. These technologies (T-cell receptor excision circles, thymic index by computed topography analysis and multiparameter flow cytometric analysis of immunophenotype) are potentially useful in clinical laboratory monitoring of human immunodeficiency virus (HIV) disease, transplantation and congenital T-cell immunodeficiency syndromes.