C5 and bacterial urinary tract infection: In the analyses of human kidney biopsies and urine, we made several observations, including: (i) urinary C5a levels are increased in UTI patients, (ii) C5aR1 is predominantly expressed in renal tubules, (iii) Man is readily detected in renal tubules across cortex and medullar in normal kidney biopsies, predominantly expressed in the luminal surface, (iv) UPEC binding to renal tubules in a mannose-dependent manner, which provide evidence supporting the possibility of C5a/C5aR1 interactions modulate Man-dependent UPEC adhesion in vivo.