Diurnal and seasonal effects on immune cell distribution and function in the pig (Sus scrofa domestica) - a diurnal species

• Applicant: Dr. Sonja Schmucker
• Subject Area: Veterinary Medical Science ; Immunology ; Animal Breeding, Animal Nutrition, Animal Husbandry
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 269213015

To secure a balanced timing of organ functions, the physiology and behavior of many species is controlled by circadian and annual rhythms. Notably, rhythmic variations are also found within the immune system leading to diurnal as well as seasonal variations in the number and functionality of blood leukocytes. These variations are likely to alter the immune competence of an organism and thus its susceptibility for diseases and might also have immunological consequences if interrupted. Knowledge about rhythmic variations in immune parameters is also of clinical relevance for defining optimal time points for vaccinations, drug intake, or the assessment of immune function in patients. Diurnal and seasonal rhythms are largely controlled by photoperiodic information. Most studies investigating photoperiodic influences on immune cells were conducted using nocturnal rodents. However, the course of two main mediators of photoperiodic information, glucocorticoids and melatonin, differ between nocturnal and diurnal species. Thus, results using nocturnal animals can hardly be transferred to diurnal species. The present study aims at the characterization of diurnal and seasonal variations in the distribution and function of peripheral immune cells in diurnal species using the pig (Sus scrofa) as a model system. Specifically, two main topics will be addressed: The analysis of photoperiodic effects on immune cell number and function and the analysis of rhythmic variations in glucocorticoid sensitivity of leukocytes as one probably underlying mechanism. For all investigations adult barrows (German landrace) will be held under well-defined light regimes only differing in duration of either 12:12 hours light:darkness, 16:8 hours light:darkness (long day) or 8:16 hours light:darkness (short day). All pigs will be fitted with indwelling cephalic vein catheters, which allows for repeated stress-free collection of blood samples. Resulting photoperiodic effects on the diurnal course of various components of the main axes of the immune system, such as innate and adaptive, cellular and humoral, primary and memory immune responses will be evaluated by in vitro and in vivo methods. The results of this study will further elucidate photoperiodic influences on immune competence and consequences for disease susceptibility of diurnal organisms.

• DFG Programme: Research Grants