Toll-like receptor-4:: Renal cells and bone marrow cells signal for neutrophil recruitment during pyelonephritis

Background. The molecular mechanisms of pathogen recognition that initiate infective pyelonephritis are poorly understood. Toll-like receptor-4 (TLR4) mutant mice infected with uropathogenic Escherichia coli lack renal CXCL2 mRNA expression, subsequent neutrophil recruitment, and renal abscess formation. Methods. We used a bone marrow transplant approach in order to investigate the contribution of TLR4 in intrinsic renal cells or bone-marrow-derived immune cells to neutrophil recruitment during infective pyelonephritis. Results. Both chimera either expressing mutant tlr4 in intrinsic renal cells and wild-type tlr4 in bone marrow-derived cells or vice versa showed an impaired response to uropathogenic E. coli infection in terms of leukocyturia and renal abscess formation when compared to tlr4 wild-type mice with congenic bone marrow transplants. Conclusion. These data suggest that TLR4 is required on both intrinsic renal cells (e. g., tubular epithelial cells) and bone marrow-derived immune cells for the control of ascending uropathogenic E. coli infection by initiating chemokine-driven renal neutrophil recruitment.