Stressful environmental conditions ape a major determinant of immune r
eactivity. This effect is pronounced in Australian National Antarctic
Research Expedition populations exposed to prolonged periods of isolat
ion in the Antarctic. Alterations of T cell function, including depres
sion of cutaneous delayed-type hypersensitivity responses and a peak 4
8.9% reduction of T cell proliferation to the mitogen phytohaemaggluti
nin, were documented during a 9-month period of isolation. T cell dysf
unction was mediated by changes within the peripheral blood mononuclea
r cell compartment, including a paradoxical atypical monocytosis assoc
iated with altered production of inflammatory cytokines. There was a s
triking reduction in the production by peripheral blood mononuclear ce
lls of the predominant pro-inflammatory monokine TNF-alpha and changes
were also detected in the production of IL-1, IL-2, IL-6, IL-1ra and
IL-10. Prolonged Antarctic isolation is also associated with altered l
atent herpesvirus homeostasis, including increased herpesvirus sheddin
g and expansion of the polyclonal latent Epstein-Barr virus-infected B
cell population. These findings have important long-term health impli
cations.