(Rocky) Jaipur Call Girl - 9521753030 Escorts Service 50% Off with Cash ON De...
host microbial interaction and toll like receptors
1. Dr. Namita Adhikari
PG Resident
Department Of Periodontology
And Oral Implantology
HOST MICROBIAL
INTERACTION
2. CONTENTS
• Introduction
• Microbial aspects of host bacterial
interaction
• Immunological aspects of
microbial-host interaction
• Molecular aspect of host microbial
interaction
• Role of mediators in periodontitis
• Summary
• Conclusion
• References
3. INTRODUCTION
Substantial microflora living in symbiosis with a
healthy host
Hundreds of species of aerobic and anaerobic bacteria
Cultural studies indicate > 700 distinct microbial
species in dental plaque
4. What is host ?
An organism which
harbors the parasite
Interaction ?
The combined effect of two or more independent
variables acting simultaneously on a dependent variable
What is bacteria?
Extremely small
usually 0.3-2.0 μm in diameter
and relatively simple
microorganisms possessing the
prokaryotic type of cell
construction
6. The host response is essentially protective, but both
hypo-responsiveness and hyper-responsiveness of
certain pathways can result in enhanced tissue
destruction.
(Bruce Philstrom 2005)
A dynamic equilibrium exists between dental plaque
bacterium and innate host defense system
7. Although microorganisms are the cause of periodontitis,
the clinical expression of the disease depends on how the
host responds to the extent and virulence of the microbial
burden
It was found that degradation of host tissue results from
this bacterial-host interaction.
(Casey Hein 2004)
12. MICROBIAL ASPECTS OF HMI
• Microbial species may or may not be pathogenic to the host
• Commensal / Periodontal pathogens
• Interaction of host with pathogenic micro-organism
Course and extent of the disease
Micro-organism exert pathogenic effects :
Direct tissue
destruction
Indirectly through stimulating
and modulating host response
13. that enable it to cause
The properties of
disease
microorganism
broadly classified into 2 categories:
enable bacterial species to colonize and invade
Can be
Factor that
host tissue
Factor that enable to cause destruction of the host tissue
Periodontal pathogens & their
virulence factors
14. How does bacteria initiate
pathogenic process???
Bacterial
Adherence
Invasion Evasion
15. Bacterial Adherence in Periodontal Environment
Data from Socransky SS, Haffajee AD: J Periodontal Res 26:195, 1991
16. Host Tissue Invasion
A key factor distinguishing pathogenic from non-pathogenic
B
ga
rc
at
m
er
-i
n
aec
ga
an
tiv
ee
nts
ep
reh
co
ies
t tissue through :
-L
U
olc
ca
elr
ia
zt
a
it
o
io
nn
in
of
ep
bia
tc
hte
lr
ii
u
a
m
pr
o
o
fvg
id
in
eg
sia
vn
alid
su
el
a
c
lu
p
soo
sr
itp
io
o
n
ck
fr
eo
tm which
they can effectively deliver toxic molecules to the host tissue
- Direct penetration into hosts epithelium / CT
Eg: A.a, P. gingivalis, F. nucleatum, T. denticola
Signifies invasion as a virulence factor
17. Significance of Invasion
• “Bursts of disease activity” in periodontitis related to phases
of bacterial invasion of the tissues
(Saglie FR,1988)
• Bacteria in the tissues enable persistence of that species in
the periodontal pocket by providing a reservoir for
recolonization
18. Bacterial Evasion of Host Defense
Mechanisms
Bacterial adherence and invasion are strategies
that help microorganisms accomplish this task
The ability to adhere allows bacteria to avoid
displacement by host secretions
Eukaryotic cell invasion disrupts the natural barriers
formed by host tissue cells
19.
20. Host Tissue Damage
Bacterial properties can be broadly classified into:
1. Those resulting in degradation of host tissues directly
2. Those causing the release of biological mediators
from host tissue cells that leads to host tissue destruction
24. Microbe-Associated Molecular Patterns
• Evolutionary-conserved molecular motifs present in
microorganisms
3 components
Microbial cell wall
Nucleic acids
Flagellin
The host immune system discriminates between self and the
resident oral flora by direct recognition of MAMPs at PRRs
(Hajishengallis G, Genco RJ 2004)
26. Tolerance Mechanism
Modulates the host response to
commensal (non-pathogenic) bacteria to
establish a balanced or homeostatic relationship
Vigilance Mechanism
Protects against periopathogenic bacteria–associated
opportunistic infections
Periodontal tissue
destruction
27. Pattern recognition receptors (PRRs)
Interact with the MAMPs and activate the immune
Proteins secreted by the host cells
Secreted by innate immune cells (neutrophils, monocytes,
m
rea
sc
pr
o
o
n
p
sh
eaig
neo
s,ud
re
b
n
o
d
d
ry
itic cells, natural killer cells)
A
Cl
rs
it
o
ic
e
a
x
lp
fr
o
ersm
seo
du
b
ny
tin
ep
git
ah
nea
lip
ap
l r
c
o
ep
ll
rs
i,
at
e
e
xi
tn
ra
n
c
a
e
tl
e
lu
im
lar
m
m
un
ae
trix cells
(
rf
eis
b
p
robs
la
est
to
s,c
c
o
elm
on
ein
ztio
nb
gla
os
rts
in
, v
oa
st
d
e
io
nb
gla
m
si
tc
s)
roorganisms
Produce different cytokines for propagation of
A
inn
fl
d
am
ad
m
ap
ativ
oe
nimmune cells (T lymphocytes, B
l
B
yr
m
id
p
g
h
e
ob
cy
etw
ese
)en the innate and adaptive immune
systems
28. • Currently, it has been seen that
PRRs also recognize
immunostimulatory by-products
derived from damaged host tissues,
known as damage-associated
molecular patterns (DAMPs).
(Kawai T, Akira S, 2011) (Cao X,
2016)
29. • Potential host cell receptors involved in recognizing
bacterial components and initiating signalling pathways that
lead to inflammatory responses include:
1. Toll-like receptors (TLRs)
2. CD14/ CD36
3. NLRs
4. CLRs
•
5.O
R
fL
th
R
esabove-mentioned bacterial and host molecules, evidence
from experimental animal studies implicate TLRs NLRs and
CD14 in periodontal tissue or alveolar bone destruction.
(Madianos et al 2005)
30.
10 functional TLRs in humans
TLR-10 -unclear biologic role
TLR- 1 -9 have been reported to be
expressed in the periodontium, in both
health and disease
2 groups acc to their localization
Plasma membrane
TLR-1,TLR-2,TLR-
4-,TLR-5,TLR-6, TLR-10
Endolysosomal membrane
TLR-3, TLR-4, TLR-7,
TLR-8, TLR-9
Toll-Like Receptors
(Kawai T, Akira S, 2010)
31. • Transmembrane proteins expressed by cells of the innate
immune system
• Involved in recognition of invading microorganisms
• Help in recognition of PAMPs expressed by infectious
agents
• Effect of stimulation of TLRs is the synthesis and
secretion of pro-inflammatory cytokines and lipid
mediators, thereby initiating the inflammatory response
32. Nucleotide-Binding Oligomerization
Domain–Like Receptors
• 22 family members comprise the intracellularly expressed
NLRs
• Localized to the cytosol
• Play a critical role in sensing invading microorganisms and
prompting the immune response
• NLRs are characterized by :
- C-terminal leucine-rich repeats that act as a sensing domain
- A central nucleotide-binding and oligomerization domain
(i.e., a NOD), and
- An N-terminal effector domain that mediates downstream
signaling
35. Role of Toll-like Receptors in Periodontitis
LPS is the major macromolecule composing the outer surface
envelope of gram-negative bacteria
LPS is made up of 3 domains (lipid A, a short core oligosaccharide,
and an O-antigen), and induces immune response through lipid A
Mammalian cells recognize LPS through homodimer protein
complex consisting of TLR-4, MD2, and accessory proteins CD14
and lipopolysaccharide-binding protein (LBP)
LBP processes and delivers LPS to CD14, which sensitizes cells for
LPS binding by the MD2-TLR-4 receptor
36. • TLR-2 has the capacity to recognize
diverse microbial macromolecules due to
forming heterodimer protein complexes
with other TLR family members
• Commonly expressed by gram-negative
bacteria are recognized by TLR-2/TLR-1
heterodimer complexes
• Expressed by gram-positive bacteria or
mycoplasmas are recognized by
TLR-2/TLR-6 heterodimer complexes
40. Complement System
Host immune response is dependent on
a functional complement system
Co-ordinates the recruitment and
activation of immune cells, bacterial
opsonization, phagocytosis, and lysis
Causes the destruction of the
microorganisms by the formation of
membrane attack complex (MAC)
43. Role of Complement in Periodontitis
• Dysregulation of complement Failure to protect the host
against pathogens and amplification of tissue damage
• Complement activation may promote periodontal inflammation
via C5a-induced vasodilation, increased vascular permeability
and flow of inflammatory exudate, and chemotactic recruitment
of inflammatory cells, especially neutrophils
• Activated complement components found at higher levels in
patients with periodontitis than healthy subject
- Carranza
44. ANTIMICROBIAL PEPTIDES
• Cationic peptides that bind to negatively
charged molecules on the microbial cell
surface
• Ultimately depolarize the cell membrane
and render it permeable, with resulting
bacterial cell death
Defensins can be classified into α-defensins
and β-defensins, based on structural
distinctions
β-Defensins 1-4 are produced by epithelial
tissues and are found in GCF and saliva
Cathelicidin LL-37 resides in neutrophils
and can be found in the gingival epithelium
45. Role of Antimicrobial Peptides in
Periodontitis
A protective role
β-defensins 1-2 observed in the upper layers of the gingival
and sulcular epithelium, adjacent to the microbial biofilm
and external environment, consistent with the innate immune
“barrier” function of the epithelium
Protection in JE provided by the higher conc. of α-
defensins and LL-37 produced by granulocytes migrating
toward the sulcus
Expression of defensins induced by whole
periopathogenic bacteria such as F. nucleatum, P.
gingivalis, A. actinomycetemcomitans and T. denticola is
largely dependent on TLR signaling,
46. Acute bacterial challenge phase:
The epithelial and vascular elements respond to the
bacterial challenge
Ac
I
uM
te in
M
flaU
mm
N
atO
ory
L
re
O
spo
G
nsI
e C
phA
aseL
:
The tissu
A
esS
res
P
po
E
nd
C
toT
thS
e ea
O
rlyF
signals
MI
Im
C
m
R
un
O
e re
B
sp
I
o
A
nse
L
ph
-a
H
se:
OST
Activation of mononuclear cells shapes the local and
s
I
yN
steT
mic
E
im
R
m
A
une
C
re
T
spI
on
O
seN
Regulation and resolution phase:
Determinants of protective components in the sulcus
and collagen balance in the tissues
47. ACUTE BACTERIAL CHALLENGE
PHASE
Intact epithelial barrier (Gingival, sulcular and JE )
Main site of initial interaction
Site of invasion of microbial pathogens
Normally an effective barrier against penetration by
bacterial products and components
Saliva
Continuous flushing of the oral cavity
Continuing supply of agglutinins and specific antibodies
48. GCF
Continuous flushing of the sulcus
Delivers all the components of blood serum complement
proteins and specific antibodies, which bathe the bacteria of
the subgingival flora
Mucosal epithelium
Crucial role in intraepithelial recruitment of phagocytes
and specific lymphocyte subsets
“Controlling bacterial penetration through the mucosal
integuments”
Keratinocyte activation to express a variety of pro-
inflammatory mediators “Inflammation”
49. Early Colonizers
Streptococci,
Actinomyces,
Capnocytophaga
LPS, fatty acids,
peptides
Transverse JE and enter connective tissue- causing
inflammation of the gingival vessels
+
Synthesis of IL-1, PGE2, MMPs by JE
Establishment of gradient of chemoattractant
signals that can guide the emigrating leukocytes
to the location of the microbial plaque
50. Junctional Epithelium
“Unique structure initially most challenged by the bacteria”
The cells have neither keratohyalin- nor membrane-coating
granules, the diffusion barrier found in most stratified
epithelia is absent
51. Cells express ICAM and LFA 3 on their surfaces even
under healthy non-inflammatory conditions
ICAM1 expression by keratinocytes can be
upregulated by pro-inflammatory cytokines but not by
lipopolysaccharide
IL-8 messenger RNA was recently found to be present in
gingival tissue and was localized primarily to the JE
52. Mucosal epithelial cells exposed to bacterial products
produces tumor necrosis factor a, IL-6 and IL-8 and broad
range of cytokines
Neural components like neuropeptides substance P and
calcitonin gene-related peptides may be a key aspect of the
early tissue response to bacterial stimuli
53. Acute Inflammatory Response Phase
• in vascular permeability
• Expression of LCAM
• Release of specific Leukocyte
activating agents
54.
55. Depending on the expression of endothelial cells of specific
adhesins: ICAM-1, VCAM-1, Mucosal cell adhesion
• L
m
eo
ul
k
eo
cc
uy
le
te
-1
entry into tissue requires increase in the
•
“
w
sth
ic
ok
si
enc
eo
ss
m
”p
o
lf
em
lee
un
kto
ac
rytr
ee
sceptors are expressed on specific
leukocyte subpopulations
Induces rolling of the leukocytes on the endoluminal aspect
of the venules
• Increases the probability of specific interactions among
vascular cell adhesion molecules and leukocyte integrins
• C
P
hra
o
n
d
c
u
eco
tif
on
ino
df
uc
th
in
eg
sele
au
dk
ho
ec
si
y
o
tn
e e
m
xo
tr
la
ev
cu
as
le
as
tio
isncb
ri
y
tid
ca
ia
lp
fe
od
resis
in
cto
ont
th
in
eue
o
x
u
u
sam
va
is
gc
ru
at
li
a
o
rn
sp
oa
fc
les
ukocytes from small venules to
JE and sulcus for maintenance of normal host defense
against microbial challenge
56. 1) the expression of ICAM-1 in epithelial
cells
Majority of cells
2) the discovery of a new family of low-
mo
1
l.
ecu
Tlia
sr
su
w
eeiin
gf
h
it
ltrate: Mononuclear cells
cytokin
(T
escw
elil
ts
h, p
B
oc
te
en
llts
,, NK cells)- “Local
cell type-spe
Ic
nifflia
cm
le
m
ua
kto
oc
ryti
enc
fi
h
le
trm
ato
et
”
actic
properties:
the ch
2e
. mG
ok
aine
in
sgaa
nc
dct
e
h
se
s n
to
eu
th
tre
op
G
h
ii
n
lg
- ival
selective interls
eu
ulk
ci
u
n
s:8Neutrophils
57. Neutrophil Response
• Protective leukocytes that phagocytose and kill bacteria
Neutrophils release large quantities of destructive enzymes
(eg,MMPs) migrate through the tissues
Also release their potent lysosomal
enzymes(elastase,lactoferrin) , cytokines, and reactive oxygen
species (ROS)
Results in the breakdown of structural components of the
periodontium and the development of collagen-depleted areas
58. IMMUNE RESPONSE PHASE
Exudate from the vessels becomes
predominated by mononuclear cells
ECAM 1 & VCAM 1 expression
Selectively binds to mononuclear cells,
allows them to exit the small blood
vessels
small lymphocytes consisting of both T
cells and B cells predominate in the
tissue infiltrate
59.
60. In the presence of antigen and various
cytokines, lymphoid cells begin to
enlarge and replicate to form clones of
CD4' and CD8+ T cells
B cells are driven to differentiate into clones
of antibody producing plasma cells
In studies of gingival specimens obtained from patients
with adult periodontitis, CD4+ cells were present in larger
numbers than CD8+ cells.
Meikle et al
63. 1. Macrophages produce chemokines that would recruit
additional monocytes and lymphocytes into the local area
2. Gingival macrophages, when stimulated, produce MMP-
destruction of ECM and may alter collagen metabolism of the
local fibroblasts
3. Activation of antigen-specific CD4+ T-lymphocytes and
differentiation to cytokine producing T cells:
-capable of providing help for B-cell differentiation
and antibody production
64. • IL-lβ, TNF-a and PGE2 are prominent components of the
periodontitis lesion and have been strongly implicated in the
pathogenesis of periodontal diseases.
Offenbacher S. Ann Periodontol. 1996
• Mediators in periodontitis are produced by activated resident
gingival cells and infiltrating leukocytes and the
complement cascade, kinin system in blood plasma and
monocytes. Garrison SW, 1989
65. Interlukin-1 family cytokines
•
•
•
•
•
IL- 1 upregulates complement and Fc receptors on
neutrophils and monocytic cells, and adhesion molecules on
fibroblasts and leukocytes.
It induces homing receptors for lymphoid cells in the
extracellular matrix and induces osteoclast formation and
bone resorption.
It enhances production of itself, matrix metalloproteinases
and prostaglandins by macrophages, fibroblasts and
neutrophils.
IL- 1 upregulates major histocompatibility complex
expression by B and T cells to facilitate their activation,
clonal expansion and immunoglobulin production.
In conjunction with tumor necrosis factor a and IL-6, 1L-1
induces production of acute-phase protiens
66. It has pleiotropic pro-inlammatory properties
IL-6 secreted by cytokines as well as resident cells (e.g., keratinocytes,
endothelial cells, fibroblasts, macrophages, lymphocytes)
Influence on monocyte differentiation into multinuclear cells
(osteoclasts) and play role in bone resorption
IL-6 also has a key role in regulating the proliferation and
differentiation of B cells and T cells, particularly the Th17 subset
Through IL-6, hormones exert their effect on gingiva
IL-6
67. Tumor Necrosis Factor Alpha
Secreted by activated macrophages as well as by
intereacting to bacterial LPS
Stimulation of endothelial cells to express selectins
Stimulate endothelial cell to produce IL-1 and upregulate
expression of ICAM-1
Mediates cell and tissue turnover by inducing MMPs
secretion
68. Prostaglandins
Lipid compounds derived from arachidonic acid
Major source is the activated macrophage, although they can
also be produced by other cells such as fibroblasts
PGE2 is a key inflammatory mediator, stimulating
production of other inflammatory mediators and cytokines
PGE2 also stimulates bone resorption and plays a key role
in periodontitis progression
69. Matrix metalloproteinase
• Proteolytic enzymes that degrade the extracellular matrix
like collagen
• Secreted by fibroblasts, keratinocytes, endothelial cells,
osteoclasts, neutrophils, and macrophages.
• In healthy tissues MMPs are produced by fibroblasts i.e
MMP-1 (collagenase-1) regulated by TIMPs
70.
71. In inflammation
Excessive quantities of MMPs are secreted by resident
cells and by the large no of infiltrating inflammatory cells
Balance between MMPs and their inhibitor disrupted
Break down of connective tissue
Predominant MMPs in periodontitis MMP-8 and MMP-
9 are secreted by neutrophils
72. TGF- β
• Produced by activated T cells
• Chemoattractant for monocytes and suppresses their
activation
• Induces production of IgA and IgG2b
• TGF-a is produced by macrophages and it serves as a
mitogen for fibroblasts and for epithelial and endothelial
cells
73. Interferon-y
• Produced by CD8+ cytotoxic T cells,
• Recruits and activates macrophages and
• Upregulates the major histocompatibility complex on virally
infected cells and targets them for killing
74. • Osteoclasts are stimulated by proinfammatory cytokines and
other mediators of infammation to resorb the alveolar bone
The balance between RANKL and OPG activity (often referred to
as the RANKL:OPG ratio) determine bone resorption or bone
formation
75. The local antibody response is activated to
assist in controlling the bacterial challenge
• As the bacterial challenge increases, the host tissues are protected
by neutrophil activity in the sulcus, facilitated by specific
antibody that is produced systemically and in the local tissue
• Early-onset periodontitis and adult periodontitis patients mount a
systemic humoral immune response to antigens of the infecting
bacteria
• In addition to the macrophage influence in shaping the T-cell and
Bcell responses within the tissues, other cells participate in
essential ways in preparing the early response.
• Production of IL-4 through antigen nonspecific mechanisms
appears to be an important aspect of the early immune response
to various pathogens
76. • Studies of the antibody response in subjects without
periodontitis found that individuals with low antibody titers
tended to have high antibody avidity and opsonic ability,
suggesting that the antibody response in subjects with health
and gingivitis is capable of providing protective functions
Polak B, Reinhardt RA. IgG antibody subclass response to Porphyrornonas gingivalis outer
membrane antigens in gingivitis and adult periodontitis. J Periodontol 1995
77. limited bacterial challenge
1.Specific bacterial biomass that directly inhibits key components of
the host defense mechanism
The local cellular and humoral responses appear to be
Interfe
sru
ef
n
fc
ic
eie
w
nittlh
yn
ce
ou
m
tr
p
o
e
p
th
en
iltfiu
nnm
cto
io
sn
t individuals to manage a
I. Presence of leukocyte killing toxins,
II. Production of short-chain fatty acids and polyamines that are
toxic to neutrophils
III. Inhibition of E-selectin upregulation on endothelial
cells
Darveau et al.
2.Some bacteria produce proteases that cleave the Fc regions of Ig or
degrade the C3 component of complement, interfering with
phagocytosis & killing
REGULATION AND RESOLUTION PHASE
78. Host response modifiers, such as
• Smoking
• systemic disease
• Genetic variation
Predispose the individual to a more destructive
response
79. Mediated by specific molecules, including a class of endogenous,
proresolving lipid mediators that includes the lipoxins, resolvins,
and protectins
Lipoxins Resolvins Protectins
lipoxygenase (LO)–derived
eicosanoids that are
generated from arachidonic
acid
• inhibit neutrophil
recruitment, chemotaxis,
and adhesion
• signal macrophages to
phagocytose the
remnants of apoptotic
cells at sites of
inflammation
derived from the omega-3
fatty acids eicosapentaenoic
acid and docosahexaenoic
acid
• inhibit neutrophil
infiltration and
transmigration
• Inhibit production of
proinflammatory
mediators
• have potent
antiinflammatory and
immunoregulatory
effects
Derived from
docosahexaenoic acid
• they reduce cytokine
expression
• also inhibit neutrophil
infiltration
81. CONCLUSION
The pathogenesis of periodontal destruction involves a complex
interplay between bacterial pathogens and the host tissues.
As disease appears to be the result of loss of regulation and a failure
to return to homeostasis, it is important to achieve a more complete
understanding of the molecular and cellular events in this complex
system.
82. REFERENCES
• Carranza’s clinical periodontology 13th edition
• Jan Lindhe, Clinical periodontology and implant dentistry, 5th
edition
• The host response to the microbial challenge in periodontitis:
assembling the players- Kenneth S. Kornman, Roy C page&
Maurizio S. Tonetti: Periodontology 2000, Vol 14
• The microbial challenge in periodontitisRichard P. Darveau,
Anne Tanner & Roy C. Page Periodontology 2000, Vol 14
• Inflammatory mediators in the pathogenesis of periodontitis
Tülay Yucel-Lindberg and Tove Båge
