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Photoperiod and temperature differently affect immune function in striped hamsters (Cricetulus barabensis)
1College of Life Sciences, Qufu Normal University, Qufu 273165, Shandong Province, China.
Summary
Short days suppressed immunity in striped hamsters, contradicting the winter immunoenhancement hypothesis. Cold stress also reduced immune function and white blood cells, potentially increasing winter mortality.
Area of Science:
- Animal physiology
- Immunology
- Seasonal adaptation
Background:
- Small mammals often enhance immune function during winter to combat cold and immunosuppression.
- The winter immunoenhancement hypothesis suggests short photoperiods boost immunity.
Purpose of the Study:
- To test the winter immunoenhancement hypothesis in striped hamsters (Cricetulus barabensis).
- To investigate the effects of short photoperiod and cold temperature on immune responses.
Main Methods:
- Thirty-four female hamsters were divided into long day/warm, long day/cold, short day/warm, and short day/cold groups.
- Immune responses, including phytohaemagglutinin (PHA) response, immunoglobulin (Ig) M and G titers, and white blood cell (WBC) counts, were measured.
- Body mass, fat mass, thymus and spleen masses, blood glucose, leptin, and corticosterone levels were also assessed.
Main Results:
- Short photoperiod reduced PHA response and IgM levels, suppressing cellular and humoral immunity.
- Cold stress decreased fat mass, WBC, IgG, and IgM titers, impacting humoral immunity.
- Neither photoperiod nor temperature affected body mass, thymus, or spleen masses.
- Corticosterone levels increased under short days, but no correlations were found between hormones/glucose and immune parameters.
Conclusions:
- Short photoperiods suppressed, rather than enhanced, immunity in striped hamsters, refuting the winter immunoenhancement hypothesis for this species.
- Cold stress negatively impacted humoral immunity and WBC, potentially contributing to higher winter mortality.
- Blood glucose, leptin, and corticosterone did not explain the observed immune changes.
