Protein deficiency and endogenous pyrogen fever

Abstract

Blood monocytes have been shown to be a major source of endogenous pyrogen (EP), the protein mediator of fever. This study describes the effects of chronic dietary protein deficiency in rabbits on the in vitro production of EP by monocytes, the time course for the dietary effects on EP production, and the possible role for serum factors in the modification of EP production and (or) development of fever. EP harvested from rabbits on a protein-free diet for 4 weeks induced normal fevers when injected i.v. into recipient animals; EP produced from the protein-deprived rabbits after 6 and 8 weeks did not elicit fevers when bioassayed. Injection of EP supernatants derived from protein-deprived rabbits and containing standard protein serum resulted in less aberrant temperature responses than injection of EP supernatants containing sera from protein-deprived rabbits. These results suggest that: (i) the production of EP by rabbit blood monocytes is sensitive to dietary protein status, (ii) the effect of protein deficiency on EP production is a threshold phenomenon, and (iii) factors present in sera of protein-deprived rabbits may modify EP-induced fever.