T regulatory and T helper 17 populations with transcription factors in pig tissues in response to chronic heat stress

Abstract

Both Treg cells (CD4+ CD25+ FOXP3+) and Th17 cells are pivotal in sustaining the immune balance in most experimental animal models. But this is not clear in heat stressed pigs. The present study was aimed at determining if T regulatory and T helper 17 populations along with transcription factors in animals such as pigs are affected by persistent heat stress. Changes in CD4⁺CD25⁺ FOXP3⁺ Treg cells of the peripheral blood mononuclear cells (PBMC), thymus, spleen, mesenteric lymph nodes, and colon lamina propria of heat-stressed pigs over 9 days were studied. Transcription and the levels of Interleukin 17 (IL-17) protein along with specific transcription factors including retinoic acid receptor related orphan receptor gamma t (RORγT) and forkhead box P3 (FOXP3) were also measured. Treg cell frequency increased in PBMC and spleen at days 1, 3 and 6, followed by a significant decrease on day 9 (p < 0.05). However, the Treg cell frequency in the thymus was seen to decrease at every measurement. (p < 0.05). A marked increase in plasma, spleen, and colon lamina propria IL-17 concentration was evident during early stages of the heat stress experiment. Transcription of RORγT and IL-17 but not FOXP3 was markedly upregulated in all the tissues examined. We concluded that heat stress affected the T regulatory and T helper 17 populations along with transcription factors in pig tissues, and that this is dependent on the duration of the thermal stress during chronic heat stress.