Immune and stress responses in C57BL/6 and C3H/HeN mouse strains following photoperiod manipulation
Gatien, M.L.; Hotchkiss, A.K.; Neigh, G.N.; Dhabhar, F.S.; Nelson, R.J.
Neuro Endocrinology Letters 25(4): 267-272
2004
ISSN/ISBN: 0172-780X PMID: 15361815 Document Number: 569324
The purpose of this study was to determine whether two different strains of mice, that are reproductively unresponsive to photoperiod, adjust immune function in response to photoperiod. Adult male C3H/HeN (C3H) and C57BL/6 (C57) mice were each placed into either a long (LD 16:8) or short (LD 8:16) photoperiod for 10 weeks (n = 15/ group). Blood was collected for flow cytometry and radioimmunoassay analysis of leukocyte numbers and corticosterone concentrations, respectively. In addition, all mice were sensitized to, and challenged with the antigen, 2,4-dinitro-1-fluorobenzene. Pinnae measurements were obtained for 7 days following challenge to determine the magnitude of the inflammatory response. Photoperiod did not affect leukocyte cell numbers in either C3H or C57 mice. C3H mice displayed higher neutrophil numbers than C57 mice (p< 0.0001), whereas C57 mice displayed higher lymphocyte numbers than C3H mice (p< 0.01). C3H mice housed in LD 16:8 had higher corticosterone concentrations than those housed in LD 8:16 (p< 0.005) and C57 mice housed in either photoperiod (p< 0.05). Photoperiod did not affect the inflammatory response, though C57 mice displayed an overall higher magnitude of response than C3H mice (p<0.05). Our results suggest that photoperiod does not alter immune function in C3H and C57 mice. Strain differences in immune function, however, were observed. Immune function is unresponsive to photoperiod in these laboratory mice, possibly indicating; a link between immune and reproductive responsiveness to photoperiod, the decreased predictive value of this annual cue to domesticated animals, or both.