Quantitative Studies of Febrile Tolerance and Levels of Specific Antibody Evoked by Bacterial Endotoxin*

A series of endotoxin injections, either in con- stant or progressively increasing increments, will induce a state of refractoriness termed endotoxin tolerance. Resistance to the febrile effect of endo- toxin is believed to be of short duration, disap- pearing within 3 weeks (2). Inasmuch as bac- terial endotoxins are potent 0 antigens and give rise to the production of specific antibody, early workers considered the possibility of a correlation between increased antibody levels and diminished febrile response (3). However, Morgan was un- able to discern a relationship between the mag- nitude of febrile reactivity and the levels of 0 ag- glutinins attained in rabbits given typhoid endo- toxin (4).