|
 |
| |
Microbiology & Infectious Diseases Seminar Series
May 2012
Topic:
MMPs, Tuberculosis and the role of the Neutrophil
Date:
Thursday, 3 May 2012 @ 11am
Speaker:
Dr.
Catherine WM Ong
Affliation:
Fellow, Department of Infectious Disease and Immunity,
Imperial College London
Convener: A/Prof Thomas
Dick
Abstract:
Objectives:
Neutrophils are the major phagocytic cells in the lungs of
patients with active pulmonary tuberculosis (TB). A matrix
degrading phenotype in TB results in tissue damage, where
the activity of matrix metalloproteinases (MMPs) is
unopposed by their tissue inhibitors (TIMPs). Factors
regulating neutrophil MMP secretion in TB in vitro
and in patients were investigated.
Methods:
Human neutrophils were infected with Mycobacterium
tuberculosis (Mtb) or stimulated with conditioned media
from Mtb- infected monocytes (CoMTB). Analysis of MMP-8/-9
secretion and TIMP-1/-2 was by ELISA, Luminex array and
zymography. Gene expression of MMP-8/9 was investigated
using real-time PCR. Neutrophil granule formation was
assessed by confocal microscopy. Induced sputum samples from
108 healthy controls and TB patients were analysed. Brain
biopsies from patients with central nervous system-TB were
studied by immunohistochemistry.
Results:
Neutrophil MMP-8/-9 secretion is upregulated by Mtb over
time and is dependent on TB multiplicity of infection. CoMTB
stimulated neutrophils resulted in a 2 and 3 fold
up-regulation of MMP-8/-9 secretion respectively (both
p<0.001). TIMP-2 is increased 2-fold (p<0.001) but not
TIMP-1. MMP-8 and -9 is increased 16 and 160 fold
respectively compared to TIMP-2. MMP-8/-9 gene expression
was increased 3.5 fold and 7 fold respectively by CoMTB
stimulation at 24 hours (both p<0.001). Confocal microscopy
demonstrated colocalisation of early endosome marker Rab-5
with MMP-8 and -9 indicating that MMP-8/-9 are newly
synthesised. MMP-8/-9 is significantly elevated in induced
sputum samples from TB patients compared to healthy controls
and both correlate with the neutrophil markers neutrophil
gelatinase associated lipocalin and myeloperoxidase. Brain
biopsy specimens from patients with CNS-TB demonstrated
neutrophils surrounding TB granulomas with MMP-8 and -9
present.
Conclusion:
Neutrophil MMP-8/-9 gene
expression and secretion is upregulated following direct
infection with TB or stimulation by monocyte-dependent TB
networks. The increase in MMP/TIMP ratio will result in a
proteolytic environment which may lead to patient morbidity
associated with tissue destruction. |
Venue
Seminar Room @ Level 3
Department of Microbiology,
MD4,
5 Science Drive 2, Singapore 117597
Admission is Free and All are Welcome
|
Seminar Coordinator
Department of Microbiology
Assoc
Prof Tan Yee Joo
@ 6516 3692
Immunology Program
Dr. Zhang Yongliang
@ 6516 6407 |
Topic:
Regulation Of T Cell Receptor Signaling Sensitivity In Thymocyte
Development, T Cell Activation And Treg Function:
The Roles Of Endogenous MHC-Peptides, PKCh
And Themis
Date:
Monday, 7 May 2012 @ 12pm
Speaker:
Professor Nicholas R.J. GASCOIGNE
Affliation:
Department of Immunology and Microbial Science, IMM1, The
Scripps Research Institute
Convener:
Prof Mary
Ng
Abstract:
Recent work has demonstrated that endogenous non-stimulatory
peptides can enhance T-cell recognition when antigen is
limiting, as occurs when viruses or tumors reduce MHC
expression as a means of immune evasion. The relative
importance of T cell receptor (TCR) or co-receptor (CD4 or
CD8) interactions with the non-stimulatory ligands in this
activation-enhancement is unclear. We have now found that
the affinity of the co-receptor for the MHC determines the
requirement for specific interaction of TCR with the
non-stimulatory ligand.
Protein kinase C
(PKC)q
has been known for a long time to function in T cell
activation within the immunological synapse, but until
recently it was not realized that
PKCh
is also important in T cell biology. It acts redundantly
with
PKCq
in thymocyte development, but is required in homeostatic
proliferation.
The mechanism for discrimination between positive and
negative or agonist selection based on recognition of self
MHC-peptide ligands in thymocyte development is unclear. It
has been a focus of this lab for many years. We have used
fluorescence resonance energy transfer (FRET) and other
imaging techniques to investigate how the developing
thymocyte can distinguish between positive or
negative-selecting ligands, finding that there are kinetic
differences in intermolecular interactions during ligand
recognition, as well as subcellular localization differences
in parts of the TCR signaling cascade. We and others
recently discovered Themis, a T-cell lineage specific
protein that regulates thymocyte development. It appears to
be important in regulation of TCR signal strength in
response to positive selecting ligands. In addition, we find
that Themis-deficient mice have defective regulatory T cells
and develop a type 2 diabetes-like disease. |
Venue
Seminar Room @ Level 3
Department of Microbiology,
MD4,
5 Science Drive 2, Singapore 117597
Admission is Free and All are Welcome
|
Seminar Coordinator
Department of Microbiology
Assoc
Prof Tan Yee Joo
@ 6516 3692
Immunology Program
Dr. Zhang Yongliang
@ 6516 6407 |
Topic:
Construction and selection of a useful, self-tolerant T cell
repertoire: the Goldilocks principle
Date:
Wednesday, 9 May 2012 @ 12pm
Speaker:
Professor Nicholas R.J. GASCOIGNE
Affliation:
Department of Immunology and Microbial Science, IMM1, The
Scripps Research Institute
Convener:
Prof Mary
Ng
Abstract:
Development of a self-tolerant T-cell receptor (TCR)
repertoire with the potential to recognize the universe of
infectious agents requires proper regulation of TCR
signaling. The repertoire is whittled down during T-cell
development in the thymus by the ability of quasi-randomly
generated TCRs to interact with self-peptides presented by
major histocompatibility complex proteins (MHCp)[1]. Low
affinity TCR interactions with self-MHCp generate weak
signals that initiate “positive selection”, causing
maturation of CD4 or
CD8ab-expressing
“single positive” (SP) thymocytes from
CD4+CD8ab+
“double positive” (DP) precursors[1,2]. These develop into
the mature naïve T-cells of the secondary lymphoid organs. TCR interaction with high affinity agonist self-ligands
results in “negative selection” and “agonist positive
selection” of specialized T-cells including gut
intraepithelial lymphocytes, iNKT-cells and nTregs[1]. The
threshold between positive and negative or agonist selection
occurs over a very small difference in TCR-MHCp affinity[3],
but the mechanism is unclear. Positive-selecting ligands
induce slower interaction than strong ligands between TCR
and CD8, and induce activation of the MAP kinase Erk within
the cell whereas strong ligands induce plasma
membrane-localized phospho-Erk[3,4]. Recent evidence
suggests that there are specific thymocyte proteins that
regulate the weak signals involved in positive
selection[2,5]. |
Venue
Seminar Room @ Level 3
Department of Microbiology,
MD4,
5 Science Drive 2, Singapore 117597
Admission is Free and All are Welcome
|
Seminar Coordinator
Department of Microbiology
Assoc
Prof Tan Yee Joo
@ 6516 3692
Immunology Program
Dr. Zhang Yongliang
@ 6516 6407 |
| |
|