Tim-3, CD9 Molecule Expressions on Natural Killer (NK) and T-Lymphocytes with NK Functions (NKT) of the Peripheral Blood at Different Trimesters of Physiological Pregnancy

Abstract

Natural killer cells (NK) and T-lymphocytes with NK functions (NKT) are the leading effectors of the mother’s immune tolerance to a semi-allogeneic fetus and have a fetal trophic effect during physiological pregnancy. Tim-3 (T-cell Ig and mucin domain-containing protein 3) and CD9 molecules play a critical role in the immunoregulatory and fetal trophic functions of NK and NKT, but their expression in peripheral blood cells has not been studied. The aim of this work was to study the expression of Tim-3 and CD9 in peripheral blood NK and NKT during physiological pregnancy. The object of the study was the peripheral blood of healthy women in I and III trimesters of a physiological pregnancy. The control group consisted of healthy non-pregnant women in the first phase of the menstrual cycle. Expression of Tim-3, CD9 molecules was analyzed by flow cytometry on regulatory NK (CD16–CD56bright) and NKT (CD16–CD56+), cytotoxic NK (CD16+CD56dim/–) and NKT (CD16+CD56+). It was found that in the first trimester of pregnancy, the total number and subpopulation composition of NK and NKT cells did not change. Tim-3 expression increased in all NK and NKT subpopulations, except for cytotoxic CD16+CD56dimNK. CD9 expression increased in all NK subpopulations, but in NKT did not differ from non-pregnant. At the same time, a direct correlation between CD9 and Tim-3 expressions was revealed in regulatory NK and NKT in the first trimester of pregnancy. In the third trimester, the regulatory CD16–CD56brightNK number increased, while cytotoxic CD16+CD56dimNK and regulatory CD16–CD56+NKT decreased compared to non-pregnant women. The number of CD16+CD56–NK did not change in I and III trimesters of a physiological pregnancy. Tim-3 expression was upregulated in all NK and cytotoxic NKT subpopulations, while CD9 was upregulated only in regulatory NKs. Thus, Tim-3 and CD9 molecule expressions of s on different NK and NKT subpopulations changed during I and III trimesters of a physiological pregnancy, which plays an important role in the regulation of their phenotype and functions.