🛡️ Immune Response
When a pathogen invades, the innate immune system responds first — neutrophils and macrophages engulf invaders within minutes. If the infection persists, adaptive immunity kicks in: T-cells and B-cell-derived antibodies mount a targeted, lasting response. Adjust virulence, immune strength, and vaccination level to see whether the infection is cleared, becomes chronic, or overwhelms the host.
Phases of the Immune Response
0–4 h (immediate): Complement proteins and mast cells release inflammatory signals. Neutrophils (blue) are first responders — they engulf and destroy bacteria by phagocytosis and release of toxic granules.
4–96 h (innate): Macrophages (green) arrive, engulfing pathogens and presenting antigens to T-cells. Natural killer cells destroy infected host cells.
3–14 days (adaptive): T-cells (orange) expand clonally and directly kill infected cells. B-cells differentiate and secrete antibodies (yellow) that neutralise pathogens. Memory cells formed here provide long-term immunity. Vaccination pre-arms the adaptive system — reducing pathogen peak dramatically.