Serum TNF alpha inhibitor in mouse typhoid.

Administration of anti-TNF alpha antiserum enhanced a sublethal infection with salmonellae of moderate virulence (Salmonella typhimurium M525) in innately susceptible (Ity(s)) BALB/c mice, indicating that TNF alpha is important in the early response which suppresses bacterial growth in the reticuloendothelial system (RES). However, only transient low levels of TNF alpha were detectable on day 3 in sera from some, but not all, sublethally infected mice. Conversely, on day 4 of the same infection, clear TNF alpha inhibitory activity was detected in some sera. Neither TNF alpha or any inhibitory activity were detected in sera of lethally infected BALB/c mice undergoing an acute, overwhelming Salmonella infection. In contrast, TNF alpha inhibitory activity, but not TNF alpha, was detected in sera of mice showing a cachectic syndrome induced by persistent high bacterial numbers following intravenous inoculation of a very high dose (2 x 10(7)) of the attenuated aro- S. typhimurium SL3261 strain.