Protection against lethal pneumococcal septicemia in pigs is associated with decreased levels of interleukin-6 in blood.

Injection of type 6b pneumococci into pigs results in a sharp rise in levels of interleukin-6 (IL-6) in blood, with an average peak value of 7,700 U/ml at 4 h and mortality in five of seven of these animals. Pretreatment at -24 h with the monocyte activator MTP-PE prevents this strong increase in IL-6 (peak value, 1,000 U/ml) and reduces mortality to zero of six animals. This suggests that MTP-PE, in addition to activating monocytes, protects animals by preventing the harmful increase of cytokines such as IL-6.