The influence of transmeridian flight on human circulating lymphocytes.

We studied the influence of transmeridian flight on the number of circulating lymphocytes, which have a circadian rhythm with low values in the daytime. The number of T lymphocytes was found to be higher than the baseline value, yet its rhythmicity was maintained after eastward flight with an 8-h time difference. The number of OKB2+ as well as Leu11+ cells were suppressed after the flight. The change in the number of T lymphocytes occurred due to the increased number of OKT4+ lymphocytes. There was no correlation between the number of OKT4+ lymphocytes and the plasma cortisol level, though plasma cortisol is a major factor in regulating the number of lymphocytes. These data showed that the number of helper/inducer T lymphocytes, B cells, and natural killer cells were affected by the physical conditions experienced after the flight. The changes in T lymphocytes were independent of those of plasma cortisol levels.