P-389 Miscarriage in recurrent pregnancy loss (RPL) patients is associated with decreased peripheral T follicular helper cells and double-positive T cells
Authors: Parvanov D , Jelezarsky L , Ganeva R , Ruseva M , Handzhiyska M , Vidolova N , Metodiev D , Stamenov G 
Published: July 2024

Abstract

Study question
Is there a relation between certain T cell subpopulations in the peripheral blood and the reproductive outcome in patients with recurrent pregnancy loss (RPL)?

Summary answer
We found that miscarriage in RPL patients is associated with low quantities of peripheral T follicular helper cells (TFH) and double-positive T cells (DPT).

What is known already
Previous studies showed that, the quantity of certain types of immune cells, such as natural killer cells and B cells has been associated with recurrent miscarriages. It is also well known that the first trimester is characterized by inflammation profile, required for successful implantation and specific Th1/Th2-type immune microenvironment. Follicular T helper cells and rare T-cells populations such as double-positive and double-negative T cells also have an important effect on the post-implantation processes. However, the effect of these specific immune cell types and their relative quantities in relation to the reproduction outcome is not fully understood.

Study design, size, duration
This observational study was performed from November 2022 to September 2023. Blood samples were collected from 65 pregnant RPL women (≥2 gestational losses) aged 28-49 years during the first trimester, at 8-10 weeks of pregnancy. Patients were followed up and divided into two groups according to their reproductive outcome: live birth or miscarriage. The exclusion criteria were history of recent inflammatory, autoimmune or oncological diseases, recent antibiotic treatment, and endometrial pathologies.

Participants/materials, setting, methods
The percentage of eight peripheral T cell subpopulations were measured by flow cytometry: T helpers (CD3+CD4+CD8-), T killers (CD3+CD4-CD8+), double-positive T cells (DPT) (CD3+CD4+CD8+), double-negative T cells (CD3+CD4-CD8-), T follicular helper cells (TFH) (CD3+CD4+CD8-CD185+), T helper type 1 (TH1) (CD4+CD183+CD196-CD194-), type 2 (TH2) (CD4+CD183-CD194+CD196-), and type 17 (TH17) (CD4+CD183-CD194+CD196+) cells. Study groups were compared by Student’s t-test using SPSS v.21 (IBM Corp., Armonk, NY, USA).

Main results and the role of chance
Among the studied RPL patients, 41 women gave live birth and 24 patients had a miscarriage after the blood sample. The mean percentage and standard deviation in the of the studied T cell subpopulations was: T helpers (49.86%±14.07%), T killers (39.49%±11.50%), DPT (2.96%±1.12%), DNT (5.61%±4.76%), TFH (8.09%±3.03%), TH1 (20.86%±8.81%), TH2 (6.22%±3.68%), and TH17 (3.93%±2.37%).The performed Student’s t-test revealed significant difference only in the percentage of TFH and DPT cells between the two studied patient groups. The percentages of TFH cells and DPT cells were significantly lower in patient group with miscarriage compared to the patient group with live birth (8.07% vs. 13.35%, p = 0.04, and 1.07% vs. 2.44%, p = 0.02, respectively).

Limitations, reasons for caution
The study was limited in sample size. It would be beneficial future studies to include more subsets of T cells, such as TH9, TH22, and T reg.

Wider implications of the findings
Low percentage of peripheral TFH and DPT cells in RPL patients could be considered as an indication for potential risk of miscarriage. Routine measurement of these immune biomarkers from the peripheral blood might be beneficial for an adequate assessment and treatment of patients with previous pregnancy losses.

Trial registration number
not applicable