Diurnal and seasonal effects on immune cell distribution and function in the pig (Sus scrofa domestica) - a diurnal species
Immunology
Animal Breeding, Animal Nutrition, Animal Husbandry
Final Report Abstract
The present study aimed at the characterization of diurnal and seasonal variations in the distribution and function of blood immune cells in diurnal species using the pig (Sus scrofa domestica) as a model system. Precisely, two main topics were addressed: The analysis of diurnal and seasonal effects on immune cell number and function and the analysis of rhythmic variations in glucocorticoid sensitivity of leukocytes as one probably underlying mechanism. We found significant diurnal rhythms in the number of most blood immune cell populations in pigs held under well-defined light conditions of 12:12 hours light:darkness. The course of these diurnal rhythms, concerning height of oscillation within the number of the various blood leukocytes as well as their peaking time, thereby, resembled data found in humans. As seasonal effects are mediated in particular by the photoperiod, thus the length of the day, we also investigated the diurnal course of different blood leukocyte types in pigs held under either 16:8 hours (long day, LD) or 8:16 hours (short day, SD) of light:darkness. In contrast to our expectations, no differences in the 24h-mean of cell numbers within the various investigated leukocyte types were found. However, higher relative amplitudes in leukocyte numbers as well as earlier peak times in relation to the time point of light-on were found in pigs held under SD compared to pigs held under LD conditions. This might reflect an important regulation mechanism: Like also known from the consequences of sleepdeprivation, our results point to the importance of properly well-timed diurnal immune cell redistribution rather than total leukocyte numbers to be the critical mechanism for maintenance of immune competence. When looking at functionality of blood leukocytes, we found highest proliferative capacity as well as greatest cytokine production of mononuclear leukocytes upon in vitro-stimulation shortly after beginning of the resting phase of the pigs. Corresponding to the higher functionality of blood leukocytes we also found lower glucocorticoid sensitivity in porcine leukocytes in the evening. This glucocorticoid sensitivity thereby seemed to critically depend on the affinity of the receptor for glucocorticoids (GR) within the cells rather than on its number, as we found lower GR affinity in porcine leukocytes during the resting phase, whereas GR number was found to be greater during rest. As glucocorticoids are regarded one major mediator transferring time information from endogenous clocks to immune cells, our results highlight the interplay of GR status and resulting glucocorticoid sensitivity in leukocytes to be one important mechanism of diurnal regulation of blood immune cell number and functionality. The results of the present project represent fundamental knowledge and path the way for further studies investigating mechanisms mediating rhythms in the immune system as well as their consequences for immune competence of diurnally active species. Further link to a list of publications: https://www.uni-hohenheim.de/organisation/person/dr-rer-nat-sonja-schmucker#publications
Publications
- Data characterizing diurnal rhythms in the number of peripheral CD8α- and CD8α+ γδ T cells in domestic pigs. Data in Brief 2017;16:843-849
Engert LC, Weiler U, Stefanski V, Schmucker SS
(See online at https://dx.doi.org/10.1016/j.dib.2017.12.013) - Glucocorticoid receptor number and affinity differ between peripheral blood mononuclear cells and granulocytes in domestic pigs. Domestic Animal Endocrinology 2017, 61:11-16
Engert LC, Weiler U, Stefanski V, Schmucker SS
(See online at https://doi.org/10.1016/j.domaniend.2017.04.004) - Diurnal rhythms in peripheral blood immune cell numbers of domestic pigs. Developmental and Comparative Immunology 2018, 73:11-20
Engert LC, Weiler U, Pfaffinger B, Stefanski V, Schmucker SS
(See online at https://doi.org/10.1016/j.dci.2017.10.003)
