How does your immune system recognize and fight bacteria?

Your immune system uses multiple layers of defense against bacteria. First, innate immunity kicks in immediately when pattern recognition receptors, like Toll-like receptors on immune cells, detect molecular signatures unique to bacteria, such as lipopolysaccharides on their outer membranes or flagellin proteins. This triggers inflammation, sending neutrophils and macrophages to engulf and destroy bacteria through phagocytosis. If bacteria persist, the adaptive immune system activates. Dendritic cells present bacterial fragments to T cells, which coordinate a targeted response. B cells produce antibodies that bind specifically to bacterial surface proteins, neutralizing them and marking them for destruction through a process called opsonization. Complement proteins also punch holes in bacterial membranes. Memory cells formed during this process allow faster responses to future infections by the same bacteria.