Investigators at University Hospital, Heidelberg, and other centers in Germany, studied the composition of the peripheral T-cell compartment and regulatory T cell (Treg) function in 30 pediatric MS patients by multicolor flow cytometry and proliferation assays. Data from pediatric patients were compared to those obtained from 26 adult patients and 67 age-matched control donors. The proportions of both naïve and Treg cells are highest in the youngest children and decrease steadily with age. Pediatric MS patients had lower numbers of naive T cells, including recent thymic emigrants, whereas percentages of memory T cells were increased. Homeostatic changes in circulating T cells paralleled the pattern in adult MS. Treatment with immunomodulatory drugs attenuated the changes. Signs of early thymic involution are found in pediatric MS, suggesting that an intrinsic compromise in thymic-dependent T-cell neogenesis might contribute to MS pathogenesis. 
COMMENT. The authors conclude that the similarities in the T-cell compartment between adult and pediatric MS patients support a shared disease pathogenesis, immunologic disease mechanism, and response to therapy. Immunomodulatory drugs used in adult-onset MS might have the same effects in pediatric MS. Further studies are warranted to address whether premature senescence of the thymus and T-cell pool occurs at the earliest detectable stages of disease in children.