Figure 1.

Assay calibration. A, linear response of ZnT8-ELISA readout with an increasing number of EndoC-βH1 (red), INS-1E (blue), and HEK293 cells (dark cyan). Solid lines, linear regressions of mean values of 4–8 replicated measurements for each data point. Error bars, S.D. The coefficient of determination (r²) for fitted regression lines ranges from 0.98 to 1.00. B, linear response of ZnT8-ELISA readout with increasing ZnT8 expression in HEK293 cells (r² = 1.00). The number of ZnT8-expressing cells in each well was increased from 0 to 10 × 10³, and the number of ZnT8-negative cells was adjusted to give a total number of 30 × 10³ cells in each well. ZnT8 expression was induced by doxycycline for 16 h. LOQ is 10× S.D. above the background. C, linear response of ZnT8-ELISA readout to purified ZnT8.