27 Thirty Years Follow Up of the Naive T Cell Compartment After Neonatal Thymectomy Due to Cardiac Surgery

Abstract

Background and aims: Surgical correction of congenital heart defects at neonatal age frequently involves total thymectomy. Initial reports suggest that neonatal thymectomy could have serious consequences, both short and long term, for the composition of the T cell compartment. Especially the naive T cell compartment would be at risk of accelerated immunosenescence. This study investigated the maintenance of the naive T cell compartment in the first three decades after neonatal thymectomy due to cardiac surgery.Methods: Thirty-nine patients were investigated after total neonatal thymectomy due to cardiac surgery. Naive and memory CD4+ and CD8+ T cell compartments were evaluated by flow cytometry, thymic output determined by TREC content and peripheral proliferation by Ki67. All data were compared to healthy controls. Presence of thymic tissue after earlier thymectomy was determined during re-operation or MRI.Results: Peripheral proliferation could not keep up with loss of thymic output in the first 10 years following thymectomy resulting in low naive T cell numbers. However, after 10 years renewed presence and activity of thymus replenished the naive T cell compartment to normal numbers for age.Conclusions: Neonatal thymectomy clearly shows reduction in naive T cell numbers in the first 10 years of life, followed by reoccurrence of thymus and subsequently re-establishment of normal naive T cell numbers in the majority of patients. As not all patients showed evidence of re-growth of functional thymus it remains prudent to save as much thymic tissue as possible during neonatal cardiac surgery.