Innate and adaptive immune system components stimulated by intravesical bacillus Calmette–Guérin

Intravesical Bacillus Calmette-Guérin (BCG) therapy is the primary immunotherapy for non-muscle invasive bladder cancer (NMIBC), functioning by stimulating a multifaceted immune response within the bladder microenvironment (Redelman-Sidi et al., 2014, Nature Reviews Urology). The process is initiated by the binding of BCG to fibronectin on the bladder wall, followed by its internalization into urothelial and tumor cells (Fuge et al., 2015, Research and Reports in Urology). This internalization triggers innate immune signaling through pattern recognition receptors (PRRs), specifically Toll-like receptors 2 and 4 (TLR2/4), which leads to the production of pro-inflammatory cytokines like IL-1, IL-6, and TNF-alpha (Pettenati & Ingersoll, 2018, Nature Reviews Urology). These cytokines recruit various immune effectors, including neutrophils, macrophages, and natural killer (NK) cells, to the bladder mucosa. Ultimately, a robust adaptive Th1-polarized immune response is established, characterized by the infiltration of CD8+ cytotoxic T lymphocytes that directly target and eliminate malignant cells (Kamat et al., 2015, Journal of Clinical Oncology). This complex interplay of innate and adaptive components is essential for the therapeutic efficacy of BCG, though it also contributes to local inflammatory side effects.

Other names

BCG-induced immune responseBCG immunotherapy pathwayIntravesical BCG responseBladder cancer immune microenvironment activation

BCG acts as a biological response modifier that triggers a complex cascade of innate and adaptive immune responses. It involves the activation of Toll-like receptors (TLRs), recruitment of neutrophils and macrophages, and the induction of a Th1-polarized T-cell response to eliminate bladder cancer cells (Redelman-Sidi et al., 2014).