Table 19.5 Basic properties of exotoxins and endotoxins
| Property | Exotoxin | Endotoxin |
| Chemical properties | Proteins, excreted by certain gram-positive or gram-negative Bacteria; generally heat-labile | Lipopolysaccharide-lipoprotein complexes (see Figures 3.33 and 3.34); released on cell lysis as part of the outer membrane of gram-negative Bacteria; extremely heat-stable |
| Mode of action; symptoms | Specific; either cytotoxin, enterotoxin, or neurotoxin with defined specific action on cells or tissues | General; fever, diarrhea, vomiting |
| Toxicity | Highly toxic, often fatal | Weakly toxic, rarely fatal |
| Immunogenicity | Highly immunogenic; stimulate the production of neutralizing antibody (antitoxin) | Relatively poor immunogen; immune response not sufficient to neutralize toxin |
| Toxoid potential | Treatment of toxin with formaldehyde will destroy toxicity, but treated toxin (toxoid) remains immunogenic | None |
| Fever potential | Do not produce fever in host | Pyrogenic, often produce fever in host |