Reproducibility of cytokine responses of fresh vs. cryopreserved cells. Data points represent cytokine responses from replicate PBMC cultures. The dotted line represents perfect agreement or concordance, and the solid line is best fit to data. Rho = Pearson correlation; CCC = Concordance Correlation Coefficient. See methods for details of statistical analysis. * p < 0.05; ** p < 0.01; *** p < 0.001.