H & L Module 1 Inflammation & Cytokines Dr. M. Bergeron
Handout & Study Guide
Inflammation & Cytokines
Learning Objectives:
1. List and describe the functions and effects of inflammation as well as the inflammatory
process in detail; list and describe the main functions of important mediators of
inflammation (bolded & highlighted); list important clinical markers of inflammation and
describe their relevance (bolded & highlighted).
2. Define cytokines and describe, in detail, how they work; list the major classes, by function,
of cytokines (bolded & highlighted); list the classes of chemokines; list examples of
cytokines in each class.
3. Define and describe the concepts of redundancy, pleiotropism, additivity, synergy, and
antagonism, as they relate to cytokines; recognize and describe examples of each.
4. List the cytokine and chemokine receptor families and provide examples of their respective
ligands.
5. Describe the signaling cascades for the following:
a. Inflammasome and PRR signaling (incl. IL-12 expression);
b. IL-1 receptor signaling;
c. Type I and Type II cytokine receptor signaling (IFN- signaling is addressed,
but Type I cytokine receptors signal the same way);
d. TNF- receptor signaling.
6. Describe the interplay between macrophages and NK cells in the activation of macrophages,
as well as IL-12 and TNF- signaling.
7. List, describe, and discuss the main functional groups of cytokines, their functions, and list
the major cytokines in those groups, as well as the role of CXCL8 (IL-8).
Bibliography
Basic Immunology: Functions and Disorders of the Immune System. 6th edition. Abbas, AK, Lichtman, AH, &
Pillai, S. Elsevier. St. Louis, MO. 2019.
Suppl.:
How the Immune System Works. 6th edition. Sompeyrac, L. Wiley-Blackwell. Hoboken, NJ. 2019.
Cellular and Molecular Immunology. 8th edition. A. K. Abbas, A. H. Lichtman, and S. Pillai. Elsevier/Saunders,
Philadelphia, PA. 2015.
Janeway’s Immunobiology. 7th edition. K. Murphy, P. Travers, and M. Walport. Garland Science, New York, NY.
2008.
Roitt’s Essential Immunology. 12th edition. P. J. Delves, S. J. Martin, D. R. Burton, and I. M Roitt. Wiley-Blackwell,
Chichester, UK. 2011.
Strongly suggested readings:
Inflammation:
Oncotarget (2018) 9(6): 7204-7218 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5805548/pdf/oncotarget-09-
7204.pdf
Cytokines:
Eur J Immunol (2007) 37(Suppl 1): S34–S45
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3140102/pdf/nihms251286.pdf
Revised September 2021 Page 1
, H & L Module 1 Inflammation & Cytokines Dr. M. Bergeron
INFLAMMATION
General concepts
·
Inflammation is the body’s response to injury. Inflammation serves to eliminate, or at least
neutralize, injurious stimuli and start the healing process so the body can go back to homeostasis.
Many different types of injury (immunological insult) can trigger inflammation: these can be
physical, chemical, biological, or even psychological. See the table below (Table 1) for further
descriptions of the types of immunological insults that exist. In this lecture (and in Semester 1), we
will focus on the acute inflammatory process seen in response to infections; later however, in third
term (Semester 3), pathologists will further categorize and refine inflammatory responses (e.g. more
detailed cellular responses, responses to chemicals, trauma, acute & chronic inflammation, aseptic,
septic, tissue repair etc.).
Oncotarget (2018) 9(6): 7204-7218
Inflammation is a quintessential process required by the immune system to perform its functions
effectively and efficiently. All immune responses occur in the context of inflammation in one way
or another; it is the environment in which leukocytes perform at their best, whether occurring during
innate or adaptive (acquired) immune responses. Inflammation provides an environment
conducive to dealing with the injury by way of (1) production, release, and accumulation of
soluble inflammatory mediators (cytokines, complement, histamine, eicosanoid lipid
mediators such as prostaglandins & leukotrienes, bradykinin etc.) in the affected site, and (2)
leukocyte activation and recruitment to the site of injury, all of which are facilitated by
microvascular events (increase in vascular permeability & leakage) initiated by the
inflammatory response near or at the site of injury. As a result of these microvascular and
inflammatory events, affected tissues swell, become erythematous (redness) and warm, which is
accompanied by sensations of pain and/or pruritus (itching) and, sometimes, loss of function, thus
the cardinal signs of inflammation: rubor, calor, dolor, tumor (and functio laesa). Swelling,
warmth and redness comes from the influx of fluid into the affected tissue, whereas the pain and
itching comes from the stimulation of sensory neurons in the affected tissue (histamine stimulates
itching sensation, bradykinin stimulates pain, and swelling stimulates baroreceptors). It is important
to consider that (1) inflammation occurs locally (restricted region of the body, e.g. sprain) and that
often inflammation occurs both locally and systemically (locally and throughout the whole body,
e.g. viral infections). We will address these somewhat separately.
Revised September 2021 Page 2
, H & L Module 1 Inflammation & Cytokines Dr. M. Bergeron
Local inflammation – Steps of the inflammatory response
1. Cognition: The inflammasome and pathogen recognition receptors
The first step in dealing with injury is recognizing that there is a problem in the first place. This
is achieved through the convergence and integration of information initiated by at least two different
on O
signals: (1) injury detection by Pathogen Recognition Receptor (PRR)-containing
inflammasomes, and (2) detection of injury by signaling PRRs engaged by Pathogen-Associated
Molecular Patterns (PAMPs) or Damage-Associated Molecular Patterns (DAMPs – also
referred to as Danger-Associated Molecular Patterns; alarmins and stressorins act in a similar
way to DAMPs, but these signal through specific receptors and are beyond the scope of this course
– consequently, we will not further discuss alarmins and stressorins).
inflammasome
The inflammasome is a multiprotein complex
↓
found in the cytosol of many cells (especially
activate
monocyte-derived phagocytic cells like monocytes,
macrophages, & dendritic cells), and its function is
capase
to activate a caspase which is required for the
↓ -
activate ILAB proteolytic activation of the inactive precursor of
InterLeukin-1-beta (IL-1) (or IL-18, but we will
-
focus on IL-1 for the purpose of this discussion;
also, just so you know, interleukins derive their name
from their capacity to mediate inter-leukocyte
communication…). The structure of the
inflammasome is such that several inactive caspase
subunits become activated following juxtaposition
with several scaffold sensor subunits, usually
Nucleotide-binding Oligomerization Domain-like
Receptors (NOD-Like Receptors or NLRs),
through the action of Apoptosis-associated Speck-
Q
like protein containing a CARD (ASC or PYCARD)
adaptor proteins; upon engagement by a ligand
(whole organism, PAMPs, or DAMPs), NLRs are
activated and oligomerize to initiate the recruitment
and clustering of ASC, which in turn allows for the
recruitment and clustering of procaspases which are
then activated by autocleavage (juxtaposed
procaspase dimers cleave one another), with the
resulting activated caspases free to go cleave their
substrate, pro-IL-1 or pro-IL-18. (for better visualization, watch the short video on the
inflammasome in Canvas)
2. Pathway activation
Inactive IL-1 (pro-IL-1) (or pro-IL-18) synthesis on the other hand, results from PRR
engagement by PAMPs. For example, engagement of Toll-Like Receptors (TLRs) by PAMPs will
-
activate the Nuclear Factor-kappa B (NF-B) signaling pathway (further discussed in the
‘CYTOKINES’ section below). NF-B transcription factor DNA binding to the promoter/enhancer
regions of the IL-1 (IL-18) gene will recruit RNApol II to yield pro-IL-1 mRNA transcription.
Revised September 2021 Page 3
, H & L Module 1 Inflammation & Cytokines Dr. M. Bergeron
The mRNA is then translated into inactive pro-IL-1. For your information only, other PRRs, such
as NLRs, also activate the NF-B pathway, whereas Scavenger Receptors (SRs) signal through
tyrosine kinases and Protein Kinase C (PKC).
paper
&
E
·I name
G -
-
↳ acite inflammation .
3. Release of inflammatory mediators
Consequently, initial release of IL-1 (i.e. the initiation of the inflammatory response) requires
two processes to occur simultaneously: (1) synthesis of pro-IL-1 and (2) caspase activation. Once
both have occurred, caspases can activate pro-IL-1 by cleavage into biologically-active IL-1.
Once released by the stimulated cell, IL-1 will engage its receptor on the surface of other cells and
trigger the activation of IL-1-responsive genes, resulting in the synthesis and release of more IL-
1, as well as numerous other proinflammatory factors. Engagement of the InterLeukin-1-
Receptor (IL-1R) on the surface of macrophages triggers the NF-B pathway (this pathway
again…), with cross-talk with the Mitogen-Activated Protein Kinase (MAPK) pathway; the
combined effect of these two pathways yields the activation of the two fol lowing transcription
factors: NF-B and Activator Protein 1 (AP-1, which are c-jun/c-fos homo or heterodimers).
Activation of these transcription
- factors leads to the synthesis and release of the following
proinflammatory cytokines, chemokines, and inflammatory mediators in the inflammatory cascade,
-
namely Tumor Necrosis Factor-alpha (TNF-), IL-6, CXCL8 (IL-8), as well as LeukoTrienes
(LT and prostaglandins) and adhesion molecules among others.
Revised September 2021 Page 4
Handout & Study Guide
Inflammation & Cytokines
Learning Objectives:
1. List and describe the functions and effects of inflammation as well as the inflammatory
process in detail; list and describe the main functions of important mediators of
inflammation (bolded & highlighted); list important clinical markers of inflammation and
describe their relevance (bolded & highlighted).
2. Define cytokines and describe, in detail, how they work; list the major classes, by function,
of cytokines (bolded & highlighted); list the classes of chemokines; list examples of
cytokines in each class.
3. Define and describe the concepts of redundancy, pleiotropism, additivity, synergy, and
antagonism, as they relate to cytokines; recognize and describe examples of each.
4. List the cytokine and chemokine receptor families and provide examples of their respective
ligands.
5. Describe the signaling cascades for the following:
a. Inflammasome and PRR signaling (incl. IL-12 expression);
b. IL-1 receptor signaling;
c. Type I and Type II cytokine receptor signaling (IFN- signaling is addressed,
but Type I cytokine receptors signal the same way);
d. TNF- receptor signaling.
6. Describe the interplay between macrophages and NK cells in the activation of macrophages,
as well as IL-12 and TNF- signaling.
7. List, describe, and discuss the main functional groups of cytokines, their functions, and list
the major cytokines in those groups, as well as the role of CXCL8 (IL-8).
Bibliography
Basic Immunology: Functions and Disorders of the Immune System. 6th edition. Abbas, AK, Lichtman, AH, &
Pillai, S. Elsevier. St. Louis, MO. 2019.
Suppl.:
How the Immune System Works. 6th edition. Sompeyrac, L. Wiley-Blackwell. Hoboken, NJ. 2019.
Cellular and Molecular Immunology. 8th edition. A. K. Abbas, A. H. Lichtman, and S. Pillai. Elsevier/Saunders,
Philadelphia, PA. 2015.
Janeway’s Immunobiology. 7th edition. K. Murphy, P. Travers, and M. Walport. Garland Science, New York, NY.
2008.
Roitt’s Essential Immunology. 12th edition. P. J. Delves, S. J. Martin, D. R. Burton, and I. M Roitt. Wiley-Blackwell,
Chichester, UK. 2011.
Strongly suggested readings:
Inflammation:
Oncotarget (2018) 9(6): 7204-7218 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5805548/pdf/oncotarget-09-
7204.pdf
Cytokines:
Eur J Immunol (2007) 37(Suppl 1): S34–S45
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3140102/pdf/nihms251286.pdf
Revised September 2021 Page 1
, H & L Module 1 Inflammation & Cytokines Dr. M. Bergeron
INFLAMMATION
General concepts
·
Inflammation is the body’s response to injury. Inflammation serves to eliminate, or at least
neutralize, injurious stimuli and start the healing process so the body can go back to homeostasis.
Many different types of injury (immunological insult) can trigger inflammation: these can be
physical, chemical, biological, or even psychological. See the table below (Table 1) for further
descriptions of the types of immunological insults that exist. In this lecture (and in Semester 1), we
will focus on the acute inflammatory process seen in response to infections; later however, in third
term (Semester 3), pathologists will further categorize and refine inflammatory responses (e.g. more
detailed cellular responses, responses to chemicals, trauma, acute & chronic inflammation, aseptic,
septic, tissue repair etc.).
Oncotarget (2018) 9(6): 7204-7218
Inflammation is a quintessential process required by the immune system to perform its functions
effectively and efficiently. All immune responses occur in the context of inflammation in one way
or another; it is the environment in which leukocytes perform at their best, whether occurring during
innate or adaptive (acquired) immune responses. Inflammation provides an environment
conducive to dealing with the injury by way of (1) production, release, and accumulation of
soluble inflammatory mediators (cytokines, complement, histamine, eicosanoid lipid
mediators such as prostaglandins & leukotrienes, bradykinin etc.) in the affected site, and (2)
leukocyte activation and recruitment to the site of injury, all of which are facilitated by
microvascular events (increase in vascular permeability & leakage) initiated by the
inflammatory response near or at the site of injury. As a result of these microvascular and
inflammatory events, affected tissues swell, become erythematous (redness) and warm, which is
accompanied by sensations of pain and/or pruritus (itching) and, sometimes, loss of function, thus
the cardinal signs of inflammation: rubor, calor, dolor, tumor (and functio laesa). Swelling,
warmth and redness comes from the influx of fluid into the affected tissue, whereas the pain and
itching comes from the stimulation of sensory neurons in the affected tissue (histamine stimulates
itching sensation, bradykinin stimulates pain, and swelling stimulates baroreceptors). It is important
to consider that (1) inflammation occurs locally (restricted region of the body, e.g. sprain) and that
often inflammation occurs both locally and systemically (locally and throughout the whole body,
e.g. viral infections). We will address these somewhat separately.
Revised September 2021 Page 2
, H & L Module 1 Inflammation & Cytokines Dr. M. Bergeron
Local inflammation – Steps of the inflammatory response
1. Cognition: The inflammasome and pathogen recognition receptors
The first step in dealing with injury is recognizing that there is a problem in the first place. This
is achieved through the convergence and integration of information initiated by at least two different
on O
signals: (1) injury detection by Pathogen Recognition Receptor (PRR)-containing
inflammasomes, and (2) detection of injury by signaling PRRs engaged by Pathogen-Associated
Molecular Patterns (PAMPs) or Damage-Associated Molecular Patterns (DAMPs – also
referred to as Danger-Associated Molecular Patterns; alarmins and stressorins act in a similar
way to DAMPs, but these signal through specific receptors and are beyond the scope of this course
– consequently, we will not further discuss alarmins and stressorins).
inflammasome
The inflammasome is a multiprotein complex
↓
found in the cytosol of many cells (especially
activate
monocyte-derived phagocytic cells like monocytes,
macrophages, & dendritic cells), and its function is
capase
to activate a caspase which is required for the
↓ -
activate ILAB proteolytic activation of the inactive precursor of
InterLeukin-1-beta (IL-1) (or IL-18, but we will
-
focus on IL-1 for the purpose of this discussion;
also, just so you know, interleukins derive their name
from their capacity to mediate inter-leukocyte
communication…). The structure of the
inflammasome is such that several inactive caspase
subunits become activated following juxtaposition
with several scaffold sensor subunits, usually
Nucleotide-binding Oligomerization Domain-like
Receptors (NOD-Like Receptors or NLRs),
through the action of Apoptosis-associated Speck-
Q
like protein containing a CARD (ASC or PYCARD)
adaptor proteins; upon engagement by a ligand
(whole organism, PAMPs, or DAMPs), NLRs are
activated and oligomerize to initiate the recruitment
and clustering of ASC, which in turn allows for the
recruitment and clustering of procaspases which are
then activated by autocleavage (juxtaposed
procaspase dimers cleave one another), with the
resulting activated caspases free to go cleave their
substrate, pro-IL-1 or pro-IL-18. (for better visualization, watch the short video on the
inflammasome in Canvas)
2. Pathway activation
Inactive IL-1 (pro-IL-1) (or pro-IL-18) synthesis on the other hand, results from PRR
engagement by PAMPs. For example, engagement of Toll-Like Receptors (TLRs) by PAMPs will
-
activate the Nuclear Factor-kappa B (NF-B) signaling pathway (further discussed in the
‘CYTOKINES’ section below). NF-B transcription factor DNA binding to the promoter/enhancer
regions of the IL-1 (IL-18) gene will recruit RNApol II to yield pro-IL-1 mRNA transcription.
Revised September 2021 Page 3
, H & L Module 1 Inflammation & Cytokines Dr. M. Bergeron
The mRNA is then translated into inactive pro-IL-1. For your information only, other PRRs, such
as NLRs, also activate the NF-B pathway, whereas Scavenger Receptors (SRs) signal through
tyrosine kinases and Protein Kinase C (PKC).
paper
&
E
·I name
G -
-
↳ acite inflammation .
3. Release of inflammatory mediators
Consequently, initial release of IL-1 (i.e. the initiation of the inflammatory response) requires
two processes to occur simultaneously: (1) synthesis of pro-IL-1 and (2) caspase activation. Once
both have occurred, caspases can activate pro-IL-1 by cleavage into biologically-active IL-1.
Once released by the stimulated cell, IL-1 will engage its receptor on the surface of other cells and
trigger the activation of IL-1-responsive genes, resulting in the synthesis and release of more IL-
1, as well as numerous other proinflammatory factors. Engagement of the InterLeukin-1-
Receptor (IL-1R) on the surface of macrophages triggers the NF-B pathway (this pathway
again…), with cross-talk with the Mitogen-Activated Protein Kinase (MAPK) pathway; the
combined effect of these two pathways yields the activation of the two fol lowing transcription
factors: NF-B and Activator Protein 1 (AP-1, which are c-jun/c-fos homo or heterodimers).
Activation of these transcription
- factors leads to the synthesis and release of the following
proinflammatory cytokines, chemokines, and inflammatory mediators in the inflammatory cascade,
-
namely Tumor Necrosis Factor-alpha (TNF-), IL-6, CXCL8 (IL-8), as well as LeukoTrienes
(LT and prostaglandins) and adhesion molecules among others.
Revised September 2021 Page 4
