Interleukin 6, which is an inflammatory marker for various diseases including COVID-19. Interleukins which mediate the leukocyte cross-talk, Upto 38ILs so far identified, named according to the order of discovery. These are involved in the pathogenesis of human inflammatory/ autoimmune diseases. Interleukins and other cytokines which have a significant role in acute inflammation are IL-1, IL-6, IL-17, TNF-α and Chemokines. IL-6, Produced by fibroblasts, monocytes/ macrophages, T-Lymphocytes, B-Lymphocytes, epithelial cells, keratinocytes and various tumor cells and Induced in normal cells by IL-1/ TNF-α / PDGF/ Viral infection.

1. Interleukin 6
Presenter: Dr Sarath Krishnan M P
Junior Resident/Biochemistry
AIIMS Rishikesh
1

2. ✘ Case study
✘ Cytokines
✘ Interleukins
✘ IL-6 Function and Family
✘ IL-6 signalling pathway
✘ IL-6 and Covid 19
✘ IL-6 and other diseases
✘ Recent Advances
✘ Summary
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3. CASE : 55yr old male admitted with a diagnosis of SARS-CoV-2
Abdominal distension and bilateral leg swelling for 10 days
O/E: T:36.8°C, PR:89 beats/min, RR: 20 breaths/min, BP:147/89 mmHg.
Chest: Clear CVS: N/L Bilateral pedal edema(+) Ascites(+)
LAB Ix: TC: 9.1x103/μl N: 6.1x103/μl L:1.5x103/μl PT/INR:14.2/1.4
aPTT:36.3 s
LDH:768 U/L CRP:49.9 mg/L D-dimer: 8,570 ng/ml Ferritin:
10,599.25 μg/l
AST:125 U/L ALP: 210 U/L AFP > 1,660 U/ml.
Anti-HCV: Non-reactive Hepatitis B surface antigen: Reactive
Baseline chest X-ray showed changes and the patient was categorized as
class 3A.
Proceeded with high-resolution computed tomography (HRCT) thorax and IL-6
to monitor for progression for severe COVID-19
3

4. *A Non-severe Coronavirus Disease 2019 Patient With Persistently High Interleukin-6 Level Nurfarah Lydia Hambali, Malehah Mohd
Noh, Shahleni Paramasivam, Tock Hing Chua, Firdaus Hayati, Alvin Oliver Payus, Tze Yuan Tee, Khairul Taufiq Rosli,
Mohammad Faruq Abd Rachman Isnadi and Benny O. Manin
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5. Cytokines
✘ Combination of two Greek words
✘ CYTO: Cell
✘ KINOS: Movement
5

6. Cytokines
✘ Low molecular weight regulatory proteins/ glycoproteins
✘ Secreted by Leukocytes and various other cells in the body in response to
a stimuli
✘ Mainly by activated lymphocytes, macrophages and dendritic cells
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Mediate
INFLAMMATORY
and IMMUNE
reactions

7. 7
Cytokine is actually a general term!!!!!
INTERLEUKINS
COLONY
STIMULATING
FACTORS
INTERFERON
CHEMOKINES
LYMPHOKINES MONOKINES

8. Properties exhibited by cytokines!!!!!
✘ Pleiotropic
✘ Redundancy
✘ Cascade induction
✘ Synergy
✘ Antagonism
8

9. Interleukins
✘ Mediate the leukocyte cross-talk
✘ Upto 38ILs so far identified, named according to the order of discovery
✘ Involved in the pathogenesis of human inflammatory/
autoimmune diseases
9

10. Interleukins and other cytokines which have a significant
role in acute inflammation are
✘ IL-1
✘ IL-6
✘ IL-17
✘ TNF-α
✘ Chemokines
10

11. ✘ Two most important cells which are the sources of most of the cytokines
are
✘ MACROPHAGES & T LYMPHOCYTES
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IL-1
IL-6
TNF-α
IL-17
TNF-β

12. INTERLEUKIN-6 (IL-6)

13. ✘ Produced by fibroblasts, monocytes/ macrophages, T-Lymphocytes, B-
Lymphocytes, epithelial cells, keratinocytes and various tumor cells
✘ Induced in normal cells by IL-1/ TNF-α / PDGF/ Viral infection
*https://www.cusabio.com/c-20945.html
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14. What is IL-6?????
✘ Polypeptide of two types of glycoprotein chains
✘ α-Chain lacks-Intracellular region and can only bind to IL-6 with low affinity
✘ Complex compound binds to the high-affinity β-chain and transmits
information to the cell through the β-chain
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15. IL-6 contains four long alpha-helical chains that are arranged in an up-up-
down-down topology
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16. Functions of IL-6
✘ Critical role in regulating the acute phase response, hematopoiesis,
inflammation, metabolic control, liver regeneration, bone metabolism and
cancer progression.
✘ IL-6 – B cell stimulating factor-2, which induces the production of
antibodies by activated B cells
✘ IL-6 binding to TGF-β induces differentiation of primary CD4+ T cells into
Th17 cells
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17. The function of IL-6 in autoimmune and chronic inflammatory diseases
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18. IL6 Family
✘ IL-6
✘ Interleukin-11 (IL-11)
✘ IL-27 p28/IL-30
✘ Interleukin 31 (IL-31)
✘ Leukaemia inhibitory factor (LIF)
✘ Oncostatin M (OSM)
✘ Ciliary neurotrophic factor (CNTF)
✘ Cardiotrophin-1 (CT-1)
✘ Neuropoietin.
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19. Interleukin-11
✘ IL-6 – type cytokine
✘ Produced by a variety of stromal cells including fibroblasts, epithelial cells
and osteoblasts
✘ Binds to a multimeric receptor complex which contains an IL-11-specific α
subunit and a 130 kDa β subunit (gp130)
✘ Stimulates hematopoiesis and hepatocyte production of acute phase
response proteins
✘ Inhibits the genesis of adipocytes, activates osteoclasts, alters neural
phenotype, stimulates tissue fibrosis and regulates chondrocyte,
synoviocyte and B cell function
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20. IL-11 structure
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21. IL-27 p28/IL-30
✘ IL-27 p28/IL-30 aka IL-27
✘ Heterodimeric cytokine consisting of an IL-12 p40-related protein and an
IL-12 p35-like protein (p38)
✘ Expressed on activated macrophages and dendritic cells
✘ IL‐27 receptor (IL-27R) expressed and is detected on
○ Naive T cells
○ Natural killer (NK) cells
○ Monocytes
○ Mast cells
○ Vascular endothelium
○ Activated B cells
○ Langerhans' cells
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22. ✘ Signals through a receptor complex consisting of IL‐27α and the protein
gp130
✘ Binding to its receptor is a cause of JAK/STAT pathway activation
✘ Expressed at sites of inflammation in autoimmune/inflammatory diseases,
such as
○ RA
○ Systemic sclerosis (SSc)
○ Inflammatory bowel disease (IBD)
○ Multiple sclerosis
○ Sarcoidosis
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23. Interleukin-31
✘ Anti-parallel four-helix bundle structure
✘ Produced by T helper type 2 cells
✘ Emerging evidence - T cell-derived cytokines are helps in the development
of an effective immune response, but when dysregulated they can promote
disease
✘ Signals through a receptor complex made of IL-31RA and Oncostatin M
receptor β (OSMRβ) expressed in immune and epithelial cells.
✘ These signals activate three pathways:
○ ERK1/2 MAP kinase
○ PI3K/AKT
○ JAK1/2
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24. Leukaemia Inhibitory Factor
✘ Is an interleukin 6 class cytokine
✘ Important roles:
○ Inducing differentiation of leukemia cell
○ Inflammatory response
○ Neuronal development
○ Embryonic implantation
○ Stem cell self-renewal
○ Cancer progression
✘ LIF protein is a monomeric glycoprotein which is often modified by
glycosylation
✘ The molecular weight of the unglycosylated LIF protein is 20–25 kDa, while
the molecular weight of the glycosylated protein is in the range of 37–63
kDa 24

25. LIF structure
25

26. Oncostatin M
✘ Aka OSM, is a member of the multifunctional cytokine IL6-type cytokine
family
✘ Produced by activated T lymphocytes, macrophages, monocytes,
neutrophils and in microglial cells.
✘ OSM is made up of 196 residues.
✘ The genes for OSM and LIF occur in tandem on the human chromosome
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✘ Both have very similar gene structures, sharing similar promoter features
and intron-exon structure 26

27. OSM structure
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28. Ciliary Neurotrophic Factor
✘ Aka CNTF
✘ Signal through intracellular chains of the gp130/LIFRβ receptor
✘ Primary structure of CNTF – Cytosolic protein with strong similarity to the
alpha-helical cytokine family - Four anti-parallel helices.
✘ Exerts its activity via complexation with CNTF receptor (CNTF-R).
✘ This complex consists of a CNTF-binding protein (CNTF-R) and two
proteins important for signal transduction
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29. CNTF structure
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30. Cardiotrophin-1
✘ Aka CT-1
✘ 201 amino acid member of the IL-6 family of cytokines
✘ Able to induce a hypertrophic response in neonatal cardiac myocytes
✘ Also detected in normal adult human lung
✘ Expressed in both fetal and adult airway smooth muscle cells.
✘ Activates gp130 dependent signaling and stimulates JAK/STAT pathway to
transduce hypertrophic and cytoprotective signals in cardiac myocytes.
✘ CT-1 has also a neurotrophic function
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31. Neuropoietin (NP)
✘ Aka cardiotrophin-2
✘ Four-helix bundle structure and signal through gp130-containing receptor
complexes.
✘ Promote embryonic motor neuron survival, neural precursor cell
proliferation, and astrocyte differentiation in vitro.
✘ NP is expressed when the expression of these other IL-6 family cytokines
is low
✘ NP may have a unique role in nervous system development.
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32. IL-6 Signalling Pathway
✘ IL-6 Signal - Initiated by binding to its receptor named IL-6R
✘ IL-6R protein has two forms in cells
○ Membrane-bound form
○ Soluble (sIL-6R) form
✘ If cells do not express IL-6R, they can be stimulated by a complex formed
by IL-6 and a sIL-6R
✘ Releasing the IL-6R protein presenting cells, which presents a gp130-
response to IL-6 cytokines
✘ IL-6 responsive cells are very sensitive to IL -6R.
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33. ✘ IL-6 forms a complex with a specific IL-6R
✘ Bind with two gp130 with high affinity to form a tetramer or hexamer IL-6/IL-
6R/gp130 complex.
✘ Then gp130 conducts biological signaling through two pathways:
○ The JAK/STAT pathway
○ The Ras/MAPK pathway.
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34. 34

35. Normal Level!!!!!
IL-6: <6ng/dl
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36. Assay in Central Lab by CHEMILUMINESCENCE
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SIEMENS ADVIA Centaur XP

37. ASSAY PROCEDURE

38. IL-6 and Diseases

39. Il-6 level increases in autoimmune, chronic inflammatory
and autoinflammatory conditions!!!!!!!
✘ COVID-19
✘ Systemic sclerosis
✘ Inflammatory myopathies
✘ Large vessel vasculitis
✘ Systemic lupus erythematosus
✘ Relapsing polychondritis
✘ Autoimmune hemolytic anemia
✘ Acquired hemophilia A
✘ Cogan’s syndrome
✘ Rheumatoid arthritis
✘ Diabetes( Type 2)
✘ Cancer
✘ Crohn’s disease
✘ Pulmonary arterial hypertension
✘ Atherosclerosis
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40. COVID-19 & IL-6
✘ IL-6 is an important cytokine with pleiotropic functions such as metabolic
regulation to inflammation, auto-immunity and acute-phase response
✘ COVID-19 patients – High levels of IL-6 due to pulmonary inflammation
and extensive lung damage
✘ COVID-19 infection has an aggressive inflammatory response with a large
amount of pro-inflammatory cytokines, known as the ‘cytokine storm’
*Relationship between IL-6 and COVID-19: to be considered during treatment Hafize Seda Vatansever & Eda Becer
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41. Cytokine storm in COVID-19
✘ Aggressive inflammatory response - “Cytokine storm.”
✘ Cytokine storm correlated directly with lung injury, multi-organ failure, and
unfavorable prognosis of severe COVID-19
✘ Most important pro-inflammatory cytokines - IL-1, TNF- α, and IL-6.
✘ “Cytokine storm” - Sudden acute increase in circulating IL-6, IL-1, TNF- α,
and interferon
✘ Lung injury - Consequence of the cytokine storm that can progress into
acute lung injury/ severe form ARDS
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42. ✘ Cytokine storm - Critical life-threating condition
✘ Characterized - Inflammation, Hyperferritinemia, Hemodynamic instability,
and multi-organ failure, and if left untreated, it leads to death.
✘ Clinical findings - Action of the proinflammatory cytokines like IL-1, IL-6, IL-
18, IFN-γ, and TNF-α
✘ Pro-inflammatory cytokines and anti-inflammatory cytokines - Elevated in
the serum of CS patients.
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43. ✘ Anti-inflammatory therapies
✘ Early recognition of CS and the prompt treatment can lead to better
outcome.
✘ IL-1 receptor antagonist – Anakinra
✘ Tocilizumab - Recombinant humanized IL-6 receptor antagonist
*The COVID-19 Cytokine Storm; What We Know So Far Dina Ragab, Haitham Salah Eldin, Mohamed Taeimah, Rasha Khattab and
Ramy Salem 43

44. *Tocilizumab among patients with COVID-19 in the intensive care unit: a multicentre observational study Noa Biran, MD Andrew Ip,
MD Jaeil Ahn, PhD Ronaldo C Go, MD Shuqi Wang, MS Shivam Mathura, BA et al.
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46. *Interleukin-6 Is a Biomarker for the Development of Fatal Severe Acute Respiratory Syndrome Coronavirus 2 Pneumonia André
Santa Cruz, Ana Mendes-Frias, Ana Isabel Oliveira, Luís Dias, Ana Rita Matos, Alexandre Carvalho, Carlos Capela et.al
46

47. Diabetes mellitus & IL-6
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*Induces by generation of inflammation by controlling
differentiation, migration, proliferation, and cell apoptosis
(*2017)

48. 48
*Impairment of the insulin-degrading enzyme (IDE) is
associated with obesity and type 2 diabetes mellitus
(T2DM)

49. Rheumatoid Arthritis & IL-6
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50. 50

51. Cancer & IL-6
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52. Summary
✘ IL-6 is a pleiotropic cytokine produced by lymphoid and nonlymphoid cells
✘ IL-6 induces a broad range of cellular and physiological responses
✘ IL-6 can be used as a marker to determine the severity of diseases
especially in COVID-19
✘ Low specificity
✘ Researches are going in the filed of IL-6R blocking in view of autoimmune
and other inflammatory diseases
52

53. References
✘ A Non-severe Coronavirus Disease 2019 Patient With Persistently High
Interleukin-6 Level Nurfarah Lydia Hambali, Malehah Mohd Noh et.al
✘ https://www.cusabio.com/c-20945.html
✘ Relationship between IL-6 and COVID-19: to be considered during
treatment Hafize Seda Vatansever & Eda Becer
✘ Interleukin-6 Is a Biomarker for the Development of Fatal Severe Acute
Respiratory Syndrome Coronavirus 2 Pneumonia André Santa Cruz, Ana
Mendes-Frias, Ana Isabel Oliveira, Luís Dias, Ana Rita Matos, Alexandre
Carvalho, Carlos Capela et.al
✘ The COVID-19 Cytokine Storm; What We Know So Far Dina Ragab,
Haitham Salah Eldin, Mohamed Taeimah, Rasha Khattab and Ramy Salem
53

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