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Immune reconstitution in children following chemotherapy for haematological malignancies: a long‐term follow‐up

Modern intensive chemotherapy for childhood haematological malignancies has led to high cure rates, but has detrimental effects on the immune system. There is little knowledge concerning long‐term recovery of the adaptive immune system. Here we studied the long‐term reconstitution of the adaptive immune system in 31 children treated for haematological malignancies between July 2000 and October 2006. We performed detailed phenotypical and functional analyses of the various B and T cell subpopulations until 5 years after chemotherapy. We show that recovery of newly‐developed transitional B cells and naive B and T cells occurred rapidly, within months, whereas recovery of the different memory B and T cell subpopulations was slower and incomplete, even after 5 years post‐chemotherapy. The speed of B and T cell recovery was age‐independent, despite a significant contribution of the thymus to T cell recovery. Plasmablast B cell levels remained above normal and immunoglobulin levels normalised within 1 week. Functional T cell responses were normal, even within the first year post‐chemotherapy. This study shows that after intensive chemotherapy for haematological malignancies in children, numbers of several memory B and T cell subpopulations were decreased on the long term, while functional T cell responses were not compromised.