Non-TcR Binding Anti-CD3 Antibodies to Promote Regulatory T Cell Activity: A Cellular Approach to Type 1 Diabetes Treatment

John Nguyen

Introduction: Type 1 diabetes mellitus, T1D, involves the autoimmune destruction of insulin producing pancreatic β cells5. In the U.S., 3 million individuals, or 3% of the population are affected with 78,000 youths diagnosed annually1. T1d affects glucose, lipid, and protein metabolism, leading to polyuria, polydipsia, hyperglycemia, and ketonuria1. Genetic components for T1D includes HLA gene substitution mutations on chromosome 6 coding MHC as well as insulin polymorphism5. Autoreactive CD4+ effector T (Teff) lymphocytes become activated by insulin peptide presentation; the HLA-DQB1*0302 allele translates a DQ8 protein in MHC class II β-chain that presents insulin B:9-23 epitope4,8. T1D couples this autoreactivity with deficient regulator T (Treg) cell activity6. Non-FcR-binding anti-cd3 antibody therapy reduces the number of autoreactive Teff cells without diminishing the number of FOXP3+ Treg cells2,7,8. Methods: Anti-PD-L1 antibody injections were used to assess PD-1 levels in non-obese diabetic (NOD) mice, and Th1 differentiation was conducted to assess in vitro for IFN-γ. In vivo proliferation of target Teff cells in these NOD mice was observed via CFSE staining. Co-culture with bone-marrow-derived dendritic cells (BMDC) was used to assess CD80 expression. ELISA for cytokine analysis, flow cytometry for FOXP3 detection, and immunofluorescence for GLUT1 detection were also used. Different T lymphocytes as well as their markers (CD3, CD4, CD8, FOXP3, PD-1, etc.) were assessed by flow cytometry from human subjects in a 2-year clinical trial. Anti-drug antibodies were assessed in these human subjects using ELISA. Results: Non-FcR binding anti-CD3 therapy decreases CD3+ T lymphocytes, including both CD4+ and CD8+ T cells2,3,7. While CD4+ T cells remained diminished, CD8+ and natural killer (NK) T cells recovered in number3. The number and activity of autoreactive Teff cells were markedly reduced. A reduced production of pro-inflammatory signals IFN-γ, IL-12, IL-7, and CD80 were observed in Teff cells after anti-CD3 antibody injection/therapy2,3,7. Treated Teffs also showed greater expression of programmed cell death protein, PD-1 as well as reduced expression of GLUT1, contributing to their diminished number3,7. These effects were not observed in Foxp3+ Treg cells7. Conclusion: Non-TcR binding anti-CD3 antibody therapy is a promising treatment method for T1D. It works by reducing inflammation and pathogenicity brought on by autoreactive Teff cells while maintaining the protective functions of Treg cells. In doing so, anti-CD3 antibody therapy provides a treatment to T1D at the most basic level. This cellular approach to treating T1D gives rise to multiple systemic benefits to patients.

 

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