645. Mucosal-Associated Invariant T cells in Renal Tissue From Patients With Recurrent Urinary Tract Infections

BACKGROUND: Mucosal associated invariant T (MAIT) cells are innate-like T-cells involved in the antibacterial and fungal response by recognizing riboflavin metabolites produced by these organisms. MAIT cells are present in blood and are highly abundant in the mucosa of the liver, lungs and intestines. In murine models of urinary tract infection (UTI), MAIT cells appear to migrate to the bladder and decrease the bacterial load. It is however unknown whether MAIT cells reside in the human urogenital tract and renal tissue and whether they play a role in the first-line defense against (recurrent) UTI (RUTI). METHODS: We used a fluorescently labelled MR1-tetramer in conjunction with 14-color flowcytometry to identify and characterize MAIT cells in renal allografts after allograft failure caused by RUTI (n = 6) or rejection (n = 6) and in healthy kidney tissue surgically removed because of renal cell carcinoma (adjacent nontumorous tissue) (n = 5). RESULTS: The mean percentage of MAIT cells within the lymphogate was higher in the RUTI kidneys (2.24%) compared with the rejection kidneys (0.14%) and the control kidneys (0.11%) (P < 0.05). Characterization of MAIT cells was impossible in some control samples due to MAIT cells counts <25 (predefined cutoff value), therefore the control group was excluded from further statistical analysis. MAIT cells in RUTI kidneys appear to have a less activated profile compared with the rejection kidneys, with a lower expression of Ki67 (P < 0.01). Though the expression of the tissue resident marker CD69/CD103 was higher in 4/6 RUTI kidneys, this difference was not significant. CONCLUSION: MAIT cells are present in renal tissue that is or has been subjected to an immunologic response. MAIT cells in RUTI kidneys display a more quiescent and in some samples more tissue resident phenotype than MAIT cells in rejection kidneys. These findings may suggest that (I) MAIT cells play a role in the first-line defense in the kidney and (II) that after RUTI, MAIT cells remain in renal tissue in a quiescent state. We postulate that this might be favorable in case of a second hit from an uropathogen. DISCLOSURES: F. Bemelman, Astellas: We received an unrestricted grant from Astellas to establish a Biobank for patients with renal diseases. The samples described in this abstract are obtained from this Biobank., Grant recipient.