Diurnal changes in certain immunity indices and plasma corticosterone concentration in white Leghorn chickens

The experiment was performed on 3 groups of White Leghorn chickens kept under L : D = 6 : 18, 12 : 12 and 18 : 6 photoperiods, respectively. One half of each group was immunized twice with SRBC. Non-immunized birds served as controls. It was found that diurnal variations in lymphocyte and granulocyte number, serum lysozyme activity, agglutinins anti-sheep red blood cells (SRBC) and anti-rabbit red blood cells (RRBC) titer and plasma corticosterone concentration depended on light conditions. Immunization affected diurnal changes in different degree, depending also on the photoperiod applied. Various interrelationships between the diurnal changes in plasma corticosterone level and those in immune parameters were found. A distinct negative correlation between plasma corticosterone concentration and lymphocyte number was seen in L : D = 12 : 12 in the non-immunized group only.