Kidney and urinary system infections: defense mechanisms and consequences of infectious diseases

The urinary system is protected by multi-level mechanisms: physical barriers (urine flow, mucus, antimicrobial peptides), innate immunity (TLRs, intercalated kidney cells, phagocytosis), specialized proteins (uromodulin), and adaptive immunity (secretory IgA, T lymphocytes). Despite this, urinary tract infections (UTIs) remain the second most common bacterial pathology in children, with an alarming increase in incidence in Russia. The consequences are catastrophic: 5–22% of patients develop scarring nephropathy; UTIs suffered in youth are associated with 15% of cases of renal failure in adolescents and 67% in women in the long term. SARS-CoV-2 increases the risk of acute kidney injury, and fungal infections (Candida, Cryptococcus) may require nephrectomy. Research on biomarkers (NGAL, cystatin C) and methods for combating biofilms is relevant.