Effect of continuous darkness on immune response [in vivo assay]

ABSTRACT

Reports denote that changes in day length enhance or suppress components of immune function in several mammalian species. The aim of the present experimental study is directed to test the hypothesis dealing with the effect of photoperiods on some immune limbs responsiveness. Twenty six male and female BALB/C mice, 5-7 weeks old, 14-18gm weight divided into two groups, test groups [n=8 mice for each sex] and control groups [n =5 for each sex]. Test groups were kept in a dark room for a month, while control groups were kept in a room where the photoperiod was day light darkness 1212hr. All studied groups immunized with 0.2ml [10% sheep red blood cells] on day 4 and 8 of the last 12 days of the experiment. The weights of all animals were measured at the beginning and the end of the experiment. Arthus reaction, delayed type hypersensitivity and serum antibody titer were assessed on day 11 and 12 of program. Significant increase [P<0.005] in body weight, index level of Arthus reaction, delayed type hypersensitivity and serum antibody titer in the test groups in comparison with the control groups were found. Data are consistent with the hypothesis that immune parameters are enhanced in short photoperiods or continuous darkness