No evidence for altered cellular immune functions in personnel deployed inthe Persian Gulf during and after the Gulf War - The Danish Gulf War study

Veterans who have participitated in the Gulf War suffer from a number of sy mptoms, collectively referred to as the Gulf War Syndrome. It has been hypo thesized that a change in the systemic cytokine balance or other changes in immunological parameters could be responsible for some of the symptoms. We analyzed the peripheral blood natural killer (NK) cell activity of 686 Gul f War personnel who had been present in the Persian Gulf area during and im mediately after the Gulf War as well as 231 gender and age-matched controls . The test material included individual samples of frozen peripheral blood mononuclear cells kept at -139 degreesC for a period of 50 to 380 days prio r to NK cell analysis of freshly thrawed cells. Significant differences in NK-cell activity were not observed by direct comparison of the levels of na tural cytotoxic activity in the two groups. However, NK-cell cytotoxicity a s such decreased due to cryopreservation. Surprisingly, the NK cells obtain ed from control donors were significantly (p < 0.0001) more sensitive to fr eezing conditions than cells from the Gulf War personnel, leaving the margi nal comparison between the two groups untrustworthy, in particular because of the marked difference between the -139<degrees>C storage times used for the two groups. Freshly thawed samples of peripheral blood T lymphocytes (C D2(+) cells) from 109 randomly selected Gulf War personnel and 68 gender- a nd age-matched controls were stimulated for 3 days with phytohemagglutinin followed by 4 h activation by phorbol ester and ionomycin, and were stained for intracellular content of interleukin-2, -5, -10 and interferon-gamma. As with natural cytotoxicity, the length of cell storage at -139 degreesC i nfluenced the production of cytokines. No significant differences in the cy tokine production between the two groups were observed when the influence o f the storage period was taken into consideration. Together, these data sug gest that no overall long-term effects on NK-cell function and T-cell cytok ine production are present in the Danish Gulf War personnel. Moreover, cryo preservation is a major potential source of bias when studying the physiolo gy of thawed NK and T cells.