Characteristics of the antigenic phenotype of monocytes in peripheral blood of patients with recurrent pregnancy loss

Recurrent pregnancy loss is a significant clinical problem affecting 1 to 5% of the population. The cause of premature loss of pregnancy remains unknown in more than half of the cases. Changes in the morphofunctional properties of monocytes can be factors leading to various pregnancy complications, in particular, to miscarriage. However, the role of monocytes in pathogenesis of recurrent pregnancy loss has not been sufficiently studied. The aim of the present study was to determine the quantitative changes in contents and antigenic phenotype of platelet-free (not bound to platelets) monocytes within whole cell population and individual subpopulations of peripheral blood monocytes in recurrent miscarriage compared to uncomplicated pregnancy. The study groups included 6-12-week pregnant women aged 24-42 years diagnosed with recurrent pregnancy loss, and women with physiological pregnancy (7-12 weeks). Monocyte content and expression of CD11b, CD86, CD162, HLA-DR, TREM-1 were determined by means of cytofluorimetric analysis in the total population and subpopulations of peripheral blood monocytes. We have found that the proportion of platelet-free monocytes in recurrent pregnancy loss was decreased (74.6%) compared to uncomplicated pregnancy (83.4%). All studied subpopulations of monocytes (classical, intermediate and non-classical) proved to contribute to these changes. Decrease in HLA-DR expression and increase in CD11b expression was observed in total cell population caused by a fraction of classical monocytes, while the expression of CD162, CD86 and TREM-1 did not change significantly. Subpopulations of monocytes contributed differently to the changes in expression levels of activation markers, being associated with recurrent miscarriage, and these changes were not always manifested in the total monocyte population. The results obtained suggest that recurrent pregnancy loss is accompanied by a decreased content of free monocytes in peripheral blood and changed antigenic phenotype of monocytes, reflecting a weakening of proinflammatory properties and increased adhesive properties of these cells. These changes may underlie the pathophysiological processes leading to premature termination of early pregnancy. Discerning the patterns of activation marker expression typical for particular obstetric disorders may contribute not only to deteciton of pathophysiological mechanisms of reproductive disorders, but also to the improvement of methods for their diagnosis, and development of pathogenetically justified methods of therapy