title: Lack of immunological responsiveness to photoperiod in a tropical rodent, Peromyscus aztecus hylocetes.
abstract: Non-tropical rodents undergo seasonal changes in immune function and disease. It has been hypothesized that seasonal fluctuations in immunity of non-tropical rodents are due to suppressed immune function during harsh winter conditions. A logical extension of this hypothesis is that seasonal changes in immunity should be reduced or absent in tropical rodents that do not experience marked seasonal fluctuations in environmental conditions; however this hypothesis remains to be tested. The present study tested the effects of photoperiod on humoral and cell-mediated immune function of male Aztec mice ( Peromyscus aztecus hylocetes). P. a. hylocetes were housed in long (L:D 16:8) or short days (L:D 8:16) for 10 weeks. Animals were then immunized with the antigen keyhole limpet hemocyanin (KLH). Serum anti-KLH immunoglobulin G (IgG) concentrations and splenocyte proliferation in response to the T-cell mitogen Concanavalin A were assessed. Short-day P. a. hylocetes did not display differences in reproductive or immune measures compared with long-day mice. Collectively, these results suggest that P. a. hylocetes are reproductively and immunologically non-responsive to photoperiod. This lack of immunological responsiveness is likely due to the relative seasonal stability of their environment compared with temperate zone species.
authors.affiliation: Center for the Integrative Study of Animal Behavior, Department of Biology and Program in Neural Science, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405, USA. gdemas@bio.indiana.edu
authors.forename: G E
authors.initials: GE
authors.lastname: Demas
authors.forename: R J
authors.initials: RJ
authors.lastname: Nelson
mesh_terms: D000818:Animals; D003208:Concanavalin A / Q000494:pharmacology; D006433:Hemocyanins / Q000008:administration & dosage; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D010542:Peromyscus / Q000276:immunology*; D017440:Photoperiod; D012621:Seasons; D013154:Spleen / Q000166:cytology / Q000187:drug effects
chemical_list: D007074:Immunoglobulin G; D003208:Concanavalin A; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin