Differential polarization and activation dynamics of systemic T helper cell subsets after aneurysmal subarachnoid hemorrhage (SAH) and during post-SAH complications

Shafqat Rasul Chaudhry,Andreas Dolf,Daniel Hänggi,Elmar Endl,Thomas Mehari Kinfe,Sajjad Muhammad,Ulf Dietrich Kahlert,Mika Niemelä

doi:10.1038/s41598-021-92873-x

Abstract

Aneurysmal subarachnoid hemorrhage (SAH) is associated with high morbidity and mortality. Devastating post-SAH complications, such as cerebral vasospasm (CVS), delayed cerebral ischemia or seizures to mention a few, are mainly responsible for the poor clinical outcome. Inflammation plays an indispensable role during early brain injury (EBI) and delayed brain injury (DBI) phases over which these complications arise. T helper cells are the major cytokine secreting cells of adaptive immunity that can polarize to multiple functionally unique sub-populations. Here, we investigate different CD4+ T cell subsets during EBI and DBI phases after SAH, and their dynamics during post-SAH complications. Peripheral venous blood from 15 SAH patients during EBI and DBI phases, was analyzed by multicolour flowcytometry. Different subsets of CD3+ CD4+ T cells were characterized by differential cell surface expression of CXCR3 and CCR6 into Th1, Th2, Th17, whereas Tregs were defined by CD25hiCD127lo. The analysis of activation states was done by the expression of stable activation markers CD38 and HLA-DR. Interestingly, compared to healthy controls, Tregs were significantly increased during both EBI and DBI phases. Different activation states of Tregs showed differential significant increase during EBI and DBI phases compared to controls. HLA-DR− CD38+ Tregs were significantly increased during DBI phase compared to EBI phase in SAH patients developing CVS, seizures and infections. However, HLA-DR− CD38− Tregs were significantly reduced during EBI phase in patients with cerebral ischemia (CI) compared to those without CI. HLA-DR− CD38− Th2 cells were significantly increased during EBI phase compared to controls. A significant reduction in Th17/Tregs and HLA-DR− CD38+ Th17/Tregs ratios was observed during both EBI and DBI phases compared to controls. While HLA-DR− CD38− Th17/Tregs and HLA-DR− CD38− Th1/Th2 ratios were impaired only during EBI phase compared to controls. In conclusion, CD4+ T cell subsets display dynamic and unique activation patterns after SAH and during the course of the manifestation of post-SAH complications, which may be helpful for the development of precision neurovascular care. However, to claim this, confirmatory studies with larger patient cohorts, ideally from different ethnic backgrounds, are required. Moreover, our descriptive study may be the grounds for subsequent lab endeavors to explore the underlying mechanisms of our observations.

Highlights

Aneurysmal subarachnoid hemorrhage (SAH) involves a sentinel subarachnoidal bleed as a consequence of a ruptured intracranial aneurysm and confers significant morbidity and mortality among other strokes[1,2,3]
Lymphocytes in the peripheral blood of SAH patients and healthy controls were identified by their low SSC and high CD45 expression and were expressed as percentage of CD45+ cells to reflect changes compared to all the leukocytes
A lymphopenic response was observed in SAH patients during both early brain injury (EBI) and delayed brain injury (DBI) phases compared to healthy controls (Fig. 1A)

Summary

Introduction

Aneurysmal subarachnoid hemorrhage (SAH) involves a sentinel subarachnoidal bleed as a consequence of a ruptured intracranial aneurysm and confers significant morbidity and mortality among other strokes[1,2,3]. A more aggressive T cell adhesion and co-stimulation profile along with increased CD4+ T cells was evident in SAH patients presenting with C VS19. These observations highlight an indispensable role of CD4+ T cells in the post-SAH pathology. Treg cells express FOXP3 and release cytokines such as IL-10, TGF-β, and IL-3527 These cells play a critical role in immune tolerance and prevention against autoimmune diseases by inhibiting the activity of all immune c ells[27]. A study found decrease in T helper cells and Treg cells in SAH patients undergoing neurosurgical microclip obliteration of their aneurysms and developing fever[14]. The current study aims to fill this gap of knowledge by characterizing the detailed dynamics of CD4+ T cell subtypes during early and delayed brain injury phases after SAH- and during post-SAH complications

Methods

Results

Discussion

Conclusion