Immune Response Simulator (2D)

This 2D simulator draws a patch of tissue from above: macrophages patrol continuously while B-cells wait dormant until an infection begins. Click "Inject pathogen" to release a swarm of invaders — macrophages converge on them immediately (innate immunity), while B-cells take several seconds to activate and start releasing antibodies that lock onto the pathogens' antigen shape, tag them, and neutralize them (adaptive immunity). Once cleared, the immune system keeps memory cells standing by, so triggering "Repeated infection" shows the antibody response spike almost instantly instead of ramping up slowly — the same principle behind vaccination. Adjust the pathogen count and immune strength sliders to see how an outbreak's size and the host's antibody production rate change how fast the infection is cleared.