Influence of mild hypothermia on cytokine gene expression in the culture of human mononuclear cells

Introduction

Clinical studies demonstrated that moderate hypothermia may improve neurological outcome after severe head injury. On the other hand hypothermia is associated with increased incidence of infection complications. Recent studies suggest that mild hypothermia directly impaires natural host defenses — leukocyte mobility, phagocytosis and reactive oxygen species production and antibody production.

Methods

In order to investigate influence of mild hypothermia on cytokine gene expression human peripheral blood mononuclear cells (PBMC) were cultivated at normothermic (37°C) and hypothermic (33°C) conditions (n = 3). Additionaly parallel cultures were stimulated with phytohaemagglutinin (PHA). Multiple cytokine mRNA expression in the cultures of PBMC was estimated using reverse transcriptase-polymerase chain reaction (RT-PCR).

Results

Our findings demonstrated that moderate hypothermia (33°C) did not alter the basic levels of IFN-γ, TNF-α, IL-1α, IL-2 and IL-10 mRNA expression in PBMC, but significantly inhibited increase in IL-2 mRNA expression caused by PHA stimulation.

Conclusion

These data strongly suggest that cytokine expression in stimulated human leukocytes can be affected by hypothermia. IL-2 is one of the key cytokines of immune response. It is known to stimulate growth and differentiation of T cells, B cells, NK cells, LAK cells, monocytes and macrophages. Hence, inhibition of IL-2 mRNA expression in PHA-stimulated PBMC by hypothermia can partially explain increased risk of infections in hypothermic patients.