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.