Presence of the diurnal rhythms of monocyte count and macrophage activities in chicks.

The diurnal rhythms of monocyte count in the peripheral blood and the nonspecific activities of peritoneal macrophages were investigated in 6- to 12-wk-old White Leghorn chicks. It was evident that monocyte count and activities of peritoneal macrophages, i.e., phagocytosis and microbicidal activity, showed clear diurnal rhythms. The rhythmic pattern of monocyte count was biphasic, unlike those of humans or mice (which exhibit a monophasic fluctuation pattern). Diurnal rhythms of phagocytic activity and microbicidal activity also showed two peaks. However, the correspondence of fluctuation patterns between phagocytic activity and microbicidal activity that have been shown in chicken heterophils was not shown in chicken macrophages. This result suggests that the activities of both functions fluctuate independently in chicken macrophages. The patterns of macrophage-nonspecific activities were not in agreement with any rhythmic patterns concerning B cell and T cell activities reported previously. This result may indicate that the accessory functions of macrophage for helper T cell activation are not involved in the formation of the rhythmic patterns of B cell and T cell functions in chicks.