Helios+CD8 T Memory Cells, Enriched in Islet-Specific Cells of T1D Fast Progressors, Express Low Levels of CD2 and Inflammatory Cytokines

Introduction and Objective: Faster progression of Type 1 Diabetes (T1D) correlates with a higher proportion of Helios+ CD8 T Memory (Tmem) cells but the cellular function of these cells is not well understood. In other disease settings, others have described Helios+ CD8 Tmem cells as regulatory and expressing low levels of inflammatory cytokines. Here, we investigate the function of Helios+ CD8 Tmem in T1D by comparing cytokine production between Helios+ and Helios- CD8 Tmem cell populations in individuals with T1D and healthy controls (HC). Methods: PBMC from 7 HC and 4 individuals with T1D were stimulated with PMA/I for 4 hours and analyzed by flow cytometry to measure co-stimulation, Helios expression and pro-inflammatory cytokines (IFNγ, TNFα, IL-2) production in CD8 Tmem cells. Results: Helios+ CD8 Tmem were more abundant in younger individuals in both HC and T1D individuals (age vs Helios+; R2=0.3889, p=0.0403). Regardless of age or disease status, the frequency of cells producing pro-inflammatory cytokines and the level of cytokine produced by an individual cell were lower in Helios+ versus Helios- cells (paired t-tests, p<0.05). We also found that the co-stimulatory molecule CD2 was lower in Helios+ as compared to Helios- CD8 Tmem cells (paired t-tests, p<0.05). Conclusion: The reduced frequency of Helios+ CD8 Tmem cells with lower cytokine production as individuals age, regardless of disease suggests the loss of a regulatory population with increasing age. This loss of a potential regulatory population begets an investigation into why Helios+ cells are higher in faster progressors and whether there may be an additional pathogenic cell driving the pathogenesis of T1D. The finding of an inverse relationship between Helios and CD2 highlights a possible role for CD2 in regulation of T1D. Overall, this work highlights the possible role of CD2 and Helios in T1D pathogenesis. Disclosure: K. Myneni: None. A.E. Wiedeman: None. S. Long: Consultant; SAB Biotherapeutics, Inc.