Immune Therapy and β-Cell Death in Type 1 Diabetes
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Figures
- FIG. 1.
Measurement of unmethylated INS DNA by real-time PCR. DNA extraction of sera, tissue, and cells and bisulfite treatment. A: DNA was isolated from serum and treated with bisulfite. The treated DNA was amplified using a first-step, methylation-insensitive reaction between bp 329 and 399 from the transcription start site. The products of this reaction were used in a second-step RT-PCR reaction with primers specific for methylated or unmethylated DNA sequences. The difference in the Ct values (methylated − unmethylated) was determined and is represented by the Δ. B: The methylated and unmethylated sequences from 10 clones from human β-cells, 14 clones from human islet cells, and 12 clones from human kidney cells are indicated at eight CpG sites (○, unmethylated cytosines; ●, methylated cytosines). The methylation pattern of the CpG sites in β-cells and kidney has previously been published (10). The bp are indicated downstream from the transcription start site. The majority of the CpG sites in purified β-cells are unmethylated, whereas there is a mixture of methylated and unmethylated sites in the products of the first-step PCR reaction from islet DNA reflecting the mixture of endocrine cells. The products of the PCR reaction with kidney DNA are predominantly methylated. C, cytosine; G, guanine; T, thymine. CG (cytosine-guanine) refers to methylated CpG sites, and TG (thymine-guanine) refers to unmethylated CpG sites.
- FIG. 2.
Unmethylated INS DNA in patients with T1D. A: The levels of unmethylated INS DNA were measured in 43 subjects with recent-onset T1D and 13 nondiabetic control (Ctl) subjects of similar age (unpaired t test, ***P = 0.001). In the patients and control subjects, unmethylated Ct values ranged from 29.8 to 37.2 and from 22.3 to 37.3, respectively, and the methylated Ct values ranged from 15.4 to 30.7 and from 15.1 to 24.2. B: The C-peptide responses to a mixed meal (area under the curve [AUC]) and the corresponding Δ are shown for the subjects with recent-onset T1D (r = 0.34, P = 0.03).
- FIG. 3.
Effects of teplizumab therapy on clinical responses and levels of unmethylated INS DNA. A and B: Percent decline in C-peptide (*P = 0.03) and increase in insulin use (**P < 0.009) from baseline are shown for drug- and placebo-treated subjects. The baseline C-peptide and insulin in the drug group was 0.53 ± 0.07 pmol/mL/min and 0.38 ± 0.03 units/kg/day, respectively, and in the placebo group 0.53 ± 0.08 pmol/mL/min and 0.38 ± 0.04 units/kg/day (P = 0.18 and 0.94). C: Relative β-cell–derived DNA levels before and after treatment with teplizumab or placebo. There was a significant reduction in the Δ in subjects treated with teplizumab (***P < 0.0001) but not placebo (P = 0.08). At baseline, the Δs in the drug- and placebo-treated groups were similar (P = 0.8). D: Subjects treated with teplizumab had a greater decline in the Δ (*P = 0.04).
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