Macrophages from Babesia and malaria infected mice are primed for monokine release.

Serum from mice infected with Babesia microti or Plasmodium vinckei petteri and given lipopolysaccharide (LPS) contained appreciable amounts of tumour necrosis factor (TNF) and lymphocyte-activating factor (LAF; Interleukin I) activity. These monokines were not noted in serum from uninfected mice given the same dose of LPS. This pattern was repeated when adherent peritoneal cells from normal or infected mice were exposed to LPS in vitro and the supernatants assayed for LAF. This indicates that the hyper-reactivity of malaria and Babesia-infected mice to LPS resides in their macrophages, and that infection with these haemoprotozoa provides the host's macrophages with the same priming stimulus for subsequent triggering of monokine release as does an injection of Bacillus Calmette Guerin.