Technical developments in immunophenotyping and function testing have greatly facilitated studies on the developing lymphocyte system in the past decade and contributed to a better interpretation of the data obtained in these studies. This is important for the correct interpretation of data obtained in paediatric patients with possible immunological diseases. The age-related differences in lymphocyte subpopulations and function imply that the available adult reference values cannot be used in children.
Conclusion: In this review we give an outline of the technical developments, their influence upon the interpretation of data, and the available literature about age-related changes in the developing lymphocyte system.