Expression of arginase 1 and tyrosine kinase Mer by blood monocytes in the dynamics of physiological pregnancy

Abstract

During pregnancy, the maternal immune system must maintain tolerance to paternal antigens, at the same time being able to eliminate pathogens, which is achieved by the weakening of adoptive immunity and the activation of innate immunity, in particular, monocytes. However, the question about the functional phenotype of monocytes, having not only pro-inflammatory, but also anti-inflammatory activity, remains open. In the given work, we have investigated the expression of M2-associated suppressive markers Arg1 and MerTK in monocyte subpopulations during uncomplicated pregnancy. Fifty-three pregnant women with uncomplicated gestation were recruited, including 14 pregnant in the 1st trimester, 20 – in the 2nd and 19 – in the third pregnancy trimester. The comparison group consisted of 15 fertile unpregnant women without aggravated somatic anamnesis, with a history of at least one childbirth. The findings showed that in the unpregnant group circulating Mo express Arg1 and MerTK, and the most relative number of Arg1+ and MerTK+ cells is concentrated in intermediate and nonclassic monocytes. During pregnancy the expression of researched molecules in monocytes reliably increases. An increase in MerTK expression is manifested by a simultaneous increase in the number of MerTK+ cells and the mean fluorescence intensity of this marker; it is observed in the 1st and 2nd trimesters and registered in all three monocyte subpopulations. At the same time, an increase in Arg1 expression is manifested either by an enhancement of Arg1+ cells, or an increase in receptor density; it is registered throughout pregnancy, including the 3rd trimester, and is maximally expressed in classic monocytes. There is a direct correlation between the number of Arg1+ and MerTK+ cells in intermediate Mo, which increases with the progression of pregnancy, and in the 3rd trimester is also detected in classical and non-classical Mo. In general, the revealed increase in the expression of Arg1 and MerTK by monocytes indicates an increase in the anti-inflammatory potential of monocytes during pregnancy, and the involvement of monocytes in the regulation of the inflammatory process at the system level. Moreover, the features of Arg1 and MerTK expression in various monocyte subpopulations during pregnancy suggest that monocytes expressing Arg1 and MerTK can mediate different mechanisms of immune adaptation during pregnancy.