P-390 The percentage of regulatory T cells is associated with T follicular helper cell quantity in the peripheral blood of pregnant women
Authors: Jelezarsky L , Parvanov D , Ganeva R , Ruseva M , Handzhiyska M , Vidolova N , Metodiev D , Stamenov G 
Published: July 2024

Abstract

Study question
Is there a relationship between the percentage of peripheral regulatory T cells (Treg) and other T cell subtypes in the first trimester of pregnancy?

Summary answer
The percentage of Treg cells showed a significant positive correlation with the quantity of T follicular helper cells (TFH).

What is known already
Regulatory T cells (Treg) play an essential role in the process of embryo implantation and maintenance of normal pregnancy. The quantity of these cells in the peripheral blood expands during the first trimester of pregnancy. Several studies report the importance of Treg in the control of the inflammatory process and in the pathophysiology of common adverse pregnancy outcomes. However, there is a scarce data about the quantitative relation between Treg and other important T sub-types during pregnancy.

Study design, size, duration
This is an observational study of 93 women, 28 to 53 years of age (mean 38 years), who had a blood sample during the first trimester (at 8-10 weeks of pregnancy). The study was conducted between November 2022 and October 2023. The exclusion criteria were history of recent inflammatory or infection disorders, recent antibiotic treatment, autoimmune diseases, oncological diseases, moderate or severe endometriosis, and endometrial polyps. Written informed consent was obtained from each participant.

Participants/materials, setting, methods
SIx peripheral T cell subtypes were measured by flow cytometry: T helpers % (CD3+CD4+CD8-/CD3+), T killers % (CD3+CD4-CD8+/CD3+), double-positive T cells % (CD3+CD4+CD8+/CD3+), double-negative T cells % (CD3+CD4-CD8-/ CD3+), T follicular helper cells % (CD3+CD4+CD8-CD185+/CD4+), T reg cells (CD4+CD8-CD25+CD127−/CD4+). Spearman’s correlation test was performed with all studied T cell subtypes in SPSS 21 package program.

Main results and the role of chance
The median percentage (range) of the studied T cell subtypes was: T helpers (51.7%, 12.1%÷91.45%), T killers (39.0%, 4.1%÷72.5%), DPT cells (1.2%, 0÷8.75), DNT cells (8.4%, 1.9%÷46.2%), Treg cells (4.6%, 1.9%÷12.7%), TFH cells (7.6%, 1.4%÷42.6%). To examine the association between the percentage of Treg cells and the other T cell subtypes, the Spearman’s Rho Correlation coefficient for non-paramentric data was used. No correlation was found between the quantity of Treg and T helpers, T killers, Total T cells, double-positive T cells (p &gt; 0.05). In contrast, the percentage of Treg showed a significant positive correlation with the percentage of TFH (R = 0.36; p = 0.01), and a significant negative correlation with double-negative T cells (R= - 0.29; p = 0.04).

Limitations, reasons for caution
The main limitation of the study is that it was carried out only in a limited period of time during the pregnancy. Thus, it would be beneficial to compare the percentage of Treg cells with other T cell sub-types in the second and third trimester of pregnancy.

Wider implications of the findings
Our study demonstrated that Treg cells have stronger association with TFH cells than with other T cell subtypes. The strength of this quantitative relationship might be important for the normal progress of pregnancy, and it remains subject of further studies.

Trial registration number
not applicable