Presence of the diurnal rythms of T cell counts and T cell activities in chicks.

The diurnal variation of T cell counts, lymphocyte mitogenic transformation of T cell with PHA in vitro, skin-response to PHA and GVHR were studied in 6 to 12 week-old chicks. It was evident that each of them showed diurnal rhythms which appearingly inherent. T cell counts and T cell transformation with PHA in vitro, skin-response to PHA and GVHR showed different diurnal rhythmic pattern, respectively. T cell counts showed higher values during light period, while T cell transformation with PHA was high at dark period. In vivo response to PHA showed two peaks, and these peaks corresponded with the peaks observed in T cell counts and T cell mitogenic transformation in respect to time. Accordingly, it is assumed that T cell counts and activity of T cells have a separate type of diurnal rhythm in chicks and diurnal rhythm of response to PHA in vivo is dependent both upon T cell counts and T cell activity. The rhythm of GVHR was opposite to that of the in vitro PHA-response. It is postulated that the activity of allo-specific cytotoxic T cells involved in GVHR may have a diurnal rhythm which is different from those of any other of subsets of T cells.