No expansion of MIS-c associated TCR Vβ 21.3+ T-cells in pediatric Post-COVID condition.

The etiology of pediatric post-COVID Condition (PPCC; i.e., long-COVID) remains elusive. Another post-infectious complication of SARS-CoV-2 in children is Multisystem Inflammatory Syndrome in Children (MIS-C) in which an expansion of polyclonal TCR Vβ 21.3+ (TRBV11-2) T-cells has been observed. Flow cytometry was performed in 86 PPCC, 32 MIS-C, 7 pediatric acute COVID-19, and 15 age matched healthy controls. Most children with MIS-C (25/32, 78%) had an enrichment of Vβ21.3+ expressing cells within activated HLA-DR+/Ki67+ T-cells. In contrast to children with MIS-C, there was no enrichment of Vβ21.3 expressing cells in PPCC patients, arguing against a shared pathophysiology.