Innate and adaptive immune system components stimulated by bacillus Calmette-Guérin

The innate and adaptive immune system components stimulated by bacillus Calmette-Guérin (BCG) comprise a broad array of molecular sensors and cellular effectors that respond to the live-attenuated Mycobacterium bovis strain. Upon administration, BCG is recognized by pattern recognition receptors (PRRs) such as Toll-like receptors 2 and 4 (TLR2/4) and the intracellular sensor NOD2, primarily on urothelial and myeloid cells (Redelman-Sidi et al., 2014). This interaction initiates a robust innate immune response characterized by the secretion of pro-inflammatory cytokines like TNF-alpha, IL-6, and IL-12, which recruit neutrophils and macrophages to the site of administration (Pettenati & Ingersoll, 2018). Subsequently, an adaptive immune response is mounted, featuring the activation of Th1-type CD4+ T cells and cytotoxic CD8+ T cells, which are essential for the long-term clearance of infected or malignant cells (Fuge et al., 2015). Furthermore, BCG is known to induce "trained immunity," an epigenetic reprogramming of innate immune cells that enhances their responsiveness to future challenges (Netea et al., 2020). This comprehensive immune activation is the therapeutic basis for BCG's use as a vaccine for tuberculosis and as the primary intravesical treatment for non-muscle invasive bladder cancer. The recruitment of Natural Killer (NK) cells also plays a vital role in the direct lysis of tumor cells through the release of perforins and granzymes. Overall, the target represents a coordinated physiological pathway rather than a single molecular entity, involving complex crosstalk between various immune cell subsets.

Other names

BCG-induced immune responseBCG-mediated immunotherapy pathwayMycobacterium bovis BCG immune stimulationBCG-induced immune components

BCG acts by binding to pattern recognition receptors (PRRs) such as TLR2, TLR4, and NOD2 on host cells, triggering a cascade of innate immune activation followed by a Th1-polarized adaptive immune response (Pettenati & Ingersoll, 2018; Redelman-Sidi et al., 2014).