Co-operation of interleukin-1 beta and tumour necrosis factor-alpha in the activation of human umbilical vein endothelial cells to inhibit Toxoplasma gondii replication.

The tachyzoites of the RH strain of Toxoplasma gondii invaded and replicated in cultured human umbilical vein endothelial cells (HUVEC). Co-treatment of the HUVEC with human recombinant interleukin-1 beta (IL-1 beta) and tumour necrosis factor-alpha (TNF-alpha) inhibited the replication of T. gondii. Growth of the parasite was measured in vitro by [3H]uracil incorporation assay 18 hr after infection. This assay showed that when cells were pretreated with IL-1 beta and TNF-alpha concentrations ranging from 1 to 100 U/ml, a high degree of inhibition was observed with a phenomenon of co-operation causing a dose-dependent inhibition of the replication of intracellular T. gondii. The mechanism(s) by which the inhibition of multiplication was effected remains to be elucidated.