| Exotoxin | Endotoxin |
| Protein in nature | Lipopolysaccharides in nature |
| Secreted both by Gram-positive and negative bacteria; diffuse into the surrounding medium | Part of Gram-negative bacterial cell wall |
| Actively secreted by the bacteria | Released by cell lysis, Not by secretion |
| Heat labile, destroyed at 60°C | Highly stable |
| Mostly enzyme-like action | Mode of action – Induces ↑IL-1 and TNF |
| Specific action on particular issues | Nonspecific (fever, shock, etc.) |
| Specific affinity for tissues | No specific affinity for tissues |
| More potent, even smaller doses fatal | Only large doses are fatal |
| Highly antigenic | Poorly antigenic |
| Neutralized by specific antibodies | Neutralization by antibodies is ineffective |
| Toxoid forms are used as a vaccine, e.g. tetanus toxoid | No effective vaccine is available using endotoxin |