Distinct Patterns in Treg and T-helper Subset Reconstitution After Autologous Hematopoietic Stem Cell Transplantation in Juvenile-onset Systemic Sclerosis Patients

Systemic sclerosis (SSc) is a refractory autoimmune disease. In recent years, autologous hematopoietic stem cell transplantation (ASCT) has been performed to treat SSc. However, the reconstitution of immune components post-ASCT in SSc have not been fully described. We tested a total of 13 samples from 4 consenting SSc patients (median age: 18.5-years-old, 3F/1M) receiving IRB-approved immunoablation (TBI 600cGy) with lung/kidney shielding and Cytoxan (n = 3) or Thiotepa (n = 1) +/– Alemtuzumab followed by ASCT (CD34+ selected). Peripheral blood samples were collected at baseline, and 3, 6, 12, 24-months post-ASCT. By flow cytometry, we focused on the FOXP3+Treg and T-helper subset reconstitution. All 4 subjects experienced significant improvement in several clinical and quality of life parameters, especially in their skin disease evident within weeks after ASCT. T-cell recovery was evident by 6-months reaching pre-ASCT levels by 2-years post-ASCT (Fig. 1A). There was an increased percentage of FOXP3+Tregs in total CD4+T cells from 3- to 6-months post-ASCT (Fig. 1B), leading to an increase in the ratio of Treg/Tcon (Fig. 1B). The higher proportions of proliferating Tregs (Fig. 1C) likely led to their increased numbers. This trend was sustained until the last evaluation at 2-years post-ASCT (Fig. 1C). In contrast, CD4+Tcons showed a relatively lower proliferation rate, leading to a higher ratio of Ki67+Treg/Ki67+Tcon compared to pre-ASCT values (Fig. 1C). Notably, there was an increased proportion of Tregs expressing the skin-homing marker cutaneous lymphocyte-associated antigen (CLA) at 3-months lasting until the last test at 2-years post-ASCT (Fig. 1D), whereas CLA+/CD4+Tcons were less plentiful. The reconstitutions of T-helper (Th) subsets were also examined according to their chemokine receptor expression. Gradually decreased numbers of Th2, Th9, and Th17 were observed in the peripheral pool (Fig. 1E,1F). Nevertheless, the absolute number of Th1 and Th22 cells returned to levels seen pre-ASCT without any recurrence or flare of SSc symptoms. In summary, an increased number of circulating FOXP3+Tregs was observed leading to an elevated Treg/Tcon ratio in the peripheral pool. Skin-homing CLA+Treg subset was further enriched correlating with improved skin scores in all patients. The decrease of the Th2/Th9/Th17 subsets in the peripheral pool post-ASCT possibly contributes to the clinically less severe autoimmune phenotype. [Display omitted]