CD8+ T cells play a key role in pathogenesis of type 1 diabetes mellitus (T1DM) and latent autoimmune diabetes in adults (LADA). LADA resembles T1DM in disease presentation except that its onset is slow. In this study, we compared patho-physiological properties of peripheral CD8+ T cells recognizing insulin derived epitopes in both the disease groups.
Insulin derived 9-mer peptides loaded with APC labeled MHC-1 dextramers (DMR) were used to detect autoreactive CD8+ T cells in the peripheral blood mononuclear cells (PBMCs) of 30 subjects, including 17 recently diagnosed T1DM, 10 LADA and 3 healthy controls. The DMR+ cells were further characterized on the basis of differentiation stages, naïve (TN), central memory (TCM), effector-memory (TEM), effector (Teff) and analyzed for intracellular expression of Perforin and Granzyme-B by flowcytometry. Further, the PBMCs were stimulated with insulin in-vitro, and reanalyzed for DMR+ CD8+ T cell subsets.
HLA-A*24 and HLA-B*08 were the most frequent alleles among all T1DM and LADA subjects with no apparent difference between the two groups. Peripheral DMR+ CD8+ T cells were detected in all T1DM and LADA subjects and frequency of DMR+ cells was comparable in T1DM (0.485±0.09 %) and LADA (0.36±0.1%) subjects. Increase in frequency of DMR+ CD8+ T cells was observed in 12 out of 17 T1DM and 3 out of 10 LADA subjects. Further, the increase in frequency of DMR+ CD8+ T cells was significantly higher in T1DM subjects (p=0.02). No significant difference was observed in the expression of Granzyme-B and Perforin in DMR+ CD8+ T cells in both the groups (p=0.42). In T1DM subjects, we also observed a strong positive correlation between C-peptide levels and frequency of the DMR+ CD8+ T cells (p=0.004).
CONCLUSIONST1DM subjects possess insulin specific autoreactive CD8+ T cells with greater proliferative potential that can be targeted for immunotherapy.