Levels of selected T lymphocyte subpopulations in peripheral blood of mares which experienced early embryonic death

The objective of the present study was to analyse the immune status of mares in the early stages of pregnancy and mares which experienced early embryonic death (EED). Forty-eight fertile purebred Arabian mares were used for the study. The mares were divided into two groups. Group I was the control group composed of 32 mares in the early stages of a normal pregnancy. Group II was composed of 12 mares which had experienced EED. In both groups, subpopulations of T lymphocytes containing CD2+, CD4+ and CD8+ were characterized using flow cytometry. The percentages of CD3+lymphocytes (adding up the cells with CD4+ and CD8+ phenotypes) and of NK cells (subtracting CD3+ cells from CD2+ lymphocytes) calculated. Due to its suppressive effects on T lymphocytes during pregnancy, TGF-β1 was determined using ELISA. The findings revealed that in mares with EED, the percentages of lymphocytes TCD2+, TCD4+, NK cells at EED, i.e. between days 14 and 21, were significantly higher compared to mares without EED. The changes in the CD4+/CD8+ ratio were similar. In the EED group, this ratio significantly increased between the 96th hour and the 30th day after ovulation compared to mares without EED. Otherwise, serum levels of TGF-β1 in the EED group were significantly lower than in the control group. The results show that mares which experienced an EED develop inflammatory reactions which activate Th1 cell immune responses.