title: Immune and stress responses in C57BL/6 and C3H/HeN mouse strains following photoperiod manipulation.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  RESULTS
  Our results suggest that photoperiod does not alter immune function in C3H and C57 mice. Strain differences in immune function, however, were observed.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Psychology, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Gatien
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Hotchkiss
authors.forename: Gretchen N
authors.initials: GN
authors.lastname: Neigh
authors.forename: Firdaus S
authors.initials: FS
authors.lastname: Dhabhar
authors.forename: Randy J
authors.initials: RJ
authors.lastname: Nelson
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001772:Blood Cell Count; D003345:Corticosterone / Q000097:blood / Q000528:radiation effects*; D006968:Hypersensitivity, Delayed / Q000276:immunology*; D007107:Immune System / Q000528:radiation effects; D007962:Leukocytes / Q000276:immunology* / Q000528:radiation effects; D008027:Light; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D017440:Photoperiod; D013045:Species Specificity; D013312:Stress, Physiological / Q000097:blood / Q000276:immunology*
chemical_list: D003345:Corticosterone