(A–E) After 3 days’ culture with additional 80 mM NaCl, 160 mM urea, or control, adhesion-depleted PBMCs were added to CFSE-labeled allogeneic HK2 human tubular epithelial cells with and without addition of NaCl as outlined in A. (B and C) After 16 hours, live HK2 cell counts were assessed by flow cytometry for NaCl (B, n = 4 from 2 donors in 2 independent experiments) and urea (n = 12 from 6 donors in 3 independent experiments, Šídák’s after ANOVA). (D and E) After 3 days’ culture with additional 80 mM NaCl or control, equal numbers of magnetically enriched CD8⁺ T cells were added to fresh allogeneic HK2 human tubular epithelial cells with and without additional 80 mM NaCl. After 16 hours, supernatant TNF-α, IL-1β, IFN-γ, and IL-10 were assessed by cytometric bead assay (n = 6 T cell donors in 3 independent experiments, Dunn’s). (F–J) PBMCs were cultured with and without stimulation with BKV peptide in the absence or presence of additional 80 mM NaCl, equimolar 160 mM urea, their combinations or control for 3 days (experimental setup in F). (G) The proportion of responsive CD137^hiCD8⁺ T cells was quantified by flow cytometry (gating in Supplemental Figure 16A) (statistical analysis of n = 8 from 4 donors in 2 independent experiments, ^#paired Student’s t test of stimulation, *Dunnett’s after ANOVA of peptide conditions). Supernatant IFN-γ (H), IL-1β, IL-18, IL-8 (I), and CCL2 (J) were assessed by cytometric bead assay (n = 5 T cell donors in independent experiments, Dunn’s of peptide conditions). (K) In single-cell suspensions of human kidney cortex and medulla, proportion of responsive CD137^hi among CD8⁺ T cells was assessed after 3 days of stimulation with BKV peptide during culture in control and additional 80 mM NaCl conditions (gating in Supplemental Figure 16B; n = 6 experiments from n = 4 donors, Dunn’s). *P < 0.05, **P < 0.01. ^#P < 0.05.