Effect of elevated environmental temperature on the antibody response of mice to Trypanosoma cruzi during the acute phase of infection

A warmer ambient temperature increases the passage of interleukin-1beta into the brains of old rats

We have demonstrated that after intraperitoneal lipopolysaccharide (LPS) injection, old rats mount fevers similar to those of young rats at an ambient temperature (Ta) of 31 degrees C, but not at 21 degrees C. The same is true for intraperitoneal or intravenous IL-1beta administration. The underlying mechanism responsible for blunted fever in old rats may be a deficiency in communication between the periphery and the brain. Possibly, peripheral cytokine actions are altered in old rats, such that the signal that reaches the brain is diminished. Here, we hypothesized that at standard laboratory temperatures, not enough IL-1beta is reaching the brain for fever to occur and that a warmer Ta would increase the influx of IL-1beta into the brain, enabling old rats to generate fever. Young (3-5 mo) and old (23-29 mo) Long-Evans rats were maintained for 3 days at either Ta 21 or 31 degrees C prior to intravenous injection with radiolabeled IL-1beta to measure passage across the blood-brain barrier. Young rats showed similar influx of IL-1beta into the brain at the two Tas, but old rats showed significant influx only at the warmer Ta. These data suggest that the lack of fever at a cool Ta may be due to a reduced influx of IL-1beta into the brain.

CD8+ T lymphocytes required for enhanced survival of Trypanosoma cruzi-infected mice at elevated environmental temperature

C3H mice, which are highly susceptible to infection with the Brazil strain of Trypanosoma cruzi, not only survive infection when maintained at elevated environmental temperature, but also experience reduced parasitemias, reduced tissue pathology, and enhanced immune responsiveness. The contribution of CD8+ T cells to this phenomenon was investigated using the in vivo cell-depletion technique. The depletion of CD8+ T lymphocytes with purified monoclonal antibody resulted in an abrogation of the protective effects of elevated environmental temperature during T. cruzi infection, as evidenced by high parasitemia levels and 100% mortality in monoclonal antibody-treated mice.