The effect of high temperature on the kinetics of lipopolysaccharide (LPS)-induced human monocytes activity in vitro.

Human peripheral blood monocytes were stimulated with lipopolysaccharide at different temperatures (34, 37 and 40 °C) and TNF-α, IL-1β and NO production was measured. Levels of TNF-α mRNA and IL-1β mRNA were measured by RT-PCR. Phagocytic activity of LPS-stimulated monocytes in terms of bacterial uptake and intracellular bacterial killing was checked at different conditions in vitro. Early elevation of TNF-α, IL-1β and NO production was found in LPS-stimulated monocytes that incubated at 40 °C followed by cells that incubated at 37 °C and lowest level was detected at 34 °C. Similar results were observed in the phagocytic activity. Expression of TNF-α mRNA and IL-1β mRNA was observed as early as 30 min post exposure to LPS in all studied temperatures and these, decreased sharply after 12 h post exposure to LPS in LPS-stimulated monocytes that incubated at 40 °C only. This report describes the striking effects of incubation temperature on activity of LPS-stimulated monocytes.