Rebooting immunity in congenital athymia: Factors impacting reconstitution with thymus implantation

Allogeneic processed thymus tissue-agdc (RETHYMIC) is the only Food and Drug Administration–approved therapy for immune reconstitution in children with congenital athymia. Evaluating factors impacting successful immune reconstitution is necessary to improve outcomes. Using data from 10 open-label, single-arm studies, this retrospective cohort study evaluated 76 children with 1-year survival following thymus tissue implantation. Variables included receipt of immune-suppressing agents, human leukocyte antigen (HLA) matching, preimplantation T cell function, and age at implantation. Outcomes include lymphocyte subsets, T cell function, and naive T cell reconstitution, defined as >100 naive T cells/mm3 at 1-year after implantation. Median total T, B, and NK cell counts at 1 year following implantation were not associated with T cell function at implantation, immune-suppressing therapies, or donor and recipient HLA matching; however, naive T cell counts were higher among those with low T cell function at time of implantation. Younger age at implantation was associated with improved immune reconstitution, supporting the importance of early diagnosis and referral for treatment.