Neonatal thymectomy; consequences for homeostasis and regulation of the immune system?

From 1977 onwards more than 100 patients have been admitted to the Wilhelmina
Children*s Hospital in Utrecht for surgical correction of a transposition of
the great arteries. During this procedure the complete thymus was excised.
Little is known about the impact of this procedure on the immune system.
Previous studies show that up to ten years after thymectomy no increase in
infectious or autoimmune diseases could be observed. New surgical techniques
and improved cardiopulmonary bypass systems have resulted in more children
being operated at an increasingly younger age. These children should have an
extensive follow-up. With innovative research techniques the immune system can
be studied accurately resulting in a better understanding of the impact of
thymectomy on the developing immune system.

This study observes the immune system of children and adults who have been
without a thymus for 3 to 30 years. Our objective is to study the role of the
thymus in the developing immune system. In addition this study will give
insight in the long term effects of neonatal thymectomy.

Informed consent will be asked of approximately 100 patients. Of these patients
one blood sample will be drawn, if possible during a regular OPD check-up
(children 3-8 years 18 ml, >8 years 27 ml). The blood samples will be isolated
and stored for experiments at a later date. The immune system will be assessed
by means of FACS analysis, thymic function by determining TREC content and
peripheral tolerance by means of measuring auto-antibodies. These experiments
will reveal the role of the thymus in the homeostasis of CD4 and CD8 cells,
both naïve and memory populations. The development of "FOXP3+ regulatory T
cells" in this setting has our particular interest. In addition to the
laboratory results, clinical data will be collected of the participating
patients. Following informed consent, the occurrence of autoimmunity,
infectious diseases and malignancies will be retrieved from the general
practitioner.

The nature of this study implies limited burden and negligible risks.
1) Time burden: approximately 45 minutes on one occasion (if possible during an
OPD visit)
2) Vena puncture: burden of the puncture, limited risk of bleeding / infection