PB0866 - Differential effects of NKT cells and T helper cells in early development of microvascular thrombosis

Monday, June 24, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Presenting Author(s)

Tonina T. Mueller, MD

Institute of Laboratory Medicine, LMU University Hospital, LMU Munich
Munich, Bayern, Germany

Co-Author(s)

JL

Junfu Luo

PhD candidate
Institute of Laboratory Medicine, LMU University Hospital, LMU Munich
Munich, Bayern, Germany
SM

Sarah Meister

MD
Institute of Laboratory Medicine, LMU University Hospital, LMU Munich
Munich, Bayern, Germany
JT

Jakob Thoss

Cand. med.
Institute of Laboratory Medicine, LMU University Hospital, LMU Munich
Munich, Bayern, Germany
MP

Mona Pilartz

PhD candidate
Institute of Laboratory Medicine, LMU University Hospital, LMU Munich
Munich, Bayern, Germany
SB

Sabrina Bortoluzzi

PhD
Institute for Clinical Chemistry and Pathobiochemistry, TU Munich, Germany
Munich, Bayern, Germany
TL

Torben LangHeinrich

PhD candidate
Institute of Laboratory Medicine, LMU University Hospital, LMU Munich
Munich, Bayern, Germany
MS

Marc Schmidt-Supprian

Professor
Institute for Clinical Chemistry and Pathobiochemistry, TU Munich, Germany
Munich, Bayern, Germany
HI

Hellen Ishikawa-Ankerhold

PhD
Department of Medicine I, LMU University Hospital, LMU Munich
Munich, Bayern, Germany
CS

Christian Schulz

Professor
Department of Medicine I, LMU University Hospital, LMU Munich
Munich, Bayern, Germany
Steffen Massberg

MD
Department of Medicine I, LMU University Hospital, LMU Munich
Munich, Bayern, Germany
BE

Bernd Engelmann

professor
Institute of Laboratory Medicine, LMU University Hospital, LMU Munich
Munich, Bayern, Germany

Background: The regulatory roles of T lymphocytes in thrombus development during systemic infections are insufficiently known.

Aims: The objective of this study was to investigate the recruitment of T cell subtypes during infection and their ability to regulate coagulation and/or fibrinolysis in liver microvessels.

Methods: C57Bl6/J, Jalpha18-/- or Valpha14-Jalpha18 mice were systemically infected with GFP+ E.coli. IHC was employed to evaluate microvascular fibrin formation, thrombus composition, immune cell recruitment and protein expression. Classical monocytes were depleted using an antiCCR2 antibody, NKT cells were identified using tetramers. Neutralizing anti-TAFI antibody inhibited TAFI activity. Mechanisms of T cell activation were dissected by neutralizing MHC-II and IL12p40. Fibrin formation and T cell association were assessed in the pulmonary microcirculation of patients with SARS-CoV-2 infections.

Results: Immune cell kinetics revealed sequential recruitment, with NKT cells being the earliest, followed by classical monocytes, neutrophils, T helper cells and B cells. The immune cells exhibited varying degrees of colocalization with fibrin. Bacteria associated predominantly with fibrin-rich areas. TF associated mainly with NKT cells, neutrophils, and classical monocytes, while uPA/uPAR colocalized with B1a and CD4+ T cells. In mice with reduced NKT cells microcirculatory fibrin deposition was lowered, similar to the effect of classical monocyte depletion. Conversely, mice with elevated NKT levels showed enhanced intravascular fibrin. Negative regulation of intravascular fibrin by activated CD4+ T cells involved IL-12p40- and MHC-II-dependent mechanisms. TAFI was closely associated with arrested CD4+ T cells, more so than with fibrin-rich areas. T cell depletion increased TAFI-fibrin association. TAFI neutralization selectively inhibited microvascular thrombosis in T cell-depleted mice. In human infections, TAFI strongly colocalized with CD4+ T cells, while TAFI in T cell-free thrombi associated with fibrin.

Conclusion(s): Microvascular thrombosis, initially triggered by NKT cells, are curtailed by T helper cells which is mediated by the ability of the T cells to prevent interaction of TAFI with fibrin.