A new method for evaluation of intracellular inhibition of multiplication or killing by mononuclear phagocytes.

A new method for evaluation of the capacity of mononuclear phagocytes to inhibit intracellular microorganisms is described. The system provides a means for assessing this effect of macrophages without concern for multiplication of extracellular organisms, effect of antibiotics, and the potential observer bias which may result from visual evaluation. It involves measurement of amount of [6-3H]UdR incorporated by Toxoplasma gondii. Differences between uptake of [6-3H]UdR by infected and uninfected macrophages can be augmented by cytosine arabinoside as this agent inhibits macrophage DNA synthesis but does not substantially alter DNA synthesis by the test organism, T. gondii.