Summary Cell-mediated immune responses were studied in 12 Antarctic and sub-Antarctic wintering groups at quarterly intervals over the period 1984-1992, using the cutaneous CMI Multitest. These populations are among the most isolated on earth. While the sub-Antarctic population at Macquarie Island had levels of responsiveness and hypoergy (9%) comparable to healthy populations in temperate zones, the Antarctic Continental group showed a level of hypoergy of 36%. There was no seasonal variation in the pattern of responses. It is concluded that the extreme and isolated environment and stress factors are responsible for the decreased immunoiogical responsiveness but the mechanisms are presently unclear. On review, one factor appears to be perceived anxiety. The high rate of hypoergy in Antarctica, where medical care is limited, may have health implications. These groups provide an excellent analogue for immunological investigations in longer term space flight.

Summary The effect of a year's isolation in Antarctica on the human mucosal immune system was assessed during the winter of 1992 at three Australian Antarctic stations: Casey, Davis and Mawson. Saliva samples were collected from each expeditioner prior to their departure from Australia and during each month in Antarctica. The concentrations of salivary immunoglobulins IgA and IgG were significantly different between the three stations, but there were no differences for salivary IgM and albumin. The mean concentrations of IgA were higher at Mawson (P < 0.008), and the mean concentrations of IgG were lower at Davis (P < 0.001) compared with the other stations. Ranges of values observed at the stations over the 12-13 months were similar. The variability of values within individuals showed station differences for salivary IgM and IgG only. The study revealed significant changes in salivary immunoglobulin values over the period in Antarctica, with similar patterns at the three Australian stations. The salivary IgA and IgM levels were lower in the first 4 months in Antarctica (January-April) and increased to maximum values in July-August, before returning to mean levels when isolation was broken in October-November. The patterns of salivary IgA and IgM suggest that stressors due to isolation may play a role in alterations of mucosal immunity in expeditioners in Antarctica.

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