UNIT 4, LESSON 5 : CYTOKINES

Cytokines Overview

• Cytokines are a diverse family of small proteins or glycoproteins, typically smaller than 30 kDa, that possess immunomodulatory capabilities.
• Cytokines act as intercellular mediators, released by cells to influence both innate and adaptive immune responses by communicating with each other.
• The two main types of immune cells which produce cytokines are helper T cells (CD4+, Th cells) and macrophages.
• They are produced by immune cells in response to pathogenic or other antigens
• Cytokines act via cell-surface receptors expressed on immune cells.
• Cytokines regulate the amplitude and duration of the immune-inflammatory response.
• They regulate the immune and inflammatory response by activating macrophages, controlling the growth and differentiation of T and B cells.

Cytokine Terminology

• Monokines are produced by mononuclear phagocytes (monocytes) and mediate innate immunity.
• Lymphokines are produced by activated T cells, primarily T helper (CD4+) cells, and regulate immune response.
• Interleukins, (ILs), are cytokines made by one leukocyte that act on another leukocyte and communicate between white blood cells (WBCs).
• Chemokines are cytokines with chemotactic activities and direct cell movement (chemotaxis).

Cytokine Biological Effect

• High-affinity binding to a cytokine receptor expressed on the surface of a target cell initiates the cytokine's action
• Cytokine actions can be autocrine (acting on the same cell), paracrine (acting on nearby cells), or endocrine (acting on distant cells).
• Cytokine receptor engagement triggers intracellular signaling cascades which lead to altered gene expression in the target cell, resulting in a biological effect.
• This biological effect may include differentiation, proliferation, or activation of the target cell.

How Cytokines Work

• Cytokines bind to high-affinity cytokine receptors on target cells which leads to intracellular signaling.
• This intracellular signaling can cause differentiation, proliferation, and activation of an immune response.
• Autocrine action affects the same cell, paracrine actions affect nearby cells, and endocrine actions affect distant cells.
• In an example of cytokine activity, IL-6 binds to IL-6R, triggering an immune response.

Cytokine Receptors & Functions

• Cytokine receptors are cell-surface glycoproteins that bind specifically to cytokines and transduce their signals, enabling cells to communicate via signals from their extracellular environment.
• Different cytokines will bind to specific receptor families
• For example, Il-6 binds through its high-affinity binding of its receptor II-6R
• Cytokines can interact in several ways, which include pleiotropic, redundant, synergic, antagonistic, and cascade induction effects

Types of Cytokine Interactions

• Pleiotropy is when one cytokine has multiple effects (e.g., IL-4 affects B cells, T cells, and macrophages).
• Redundancy is when multiple cytokines perform the same function (e.g., IL-2, IL-4, IL-5 all promote B cell proliferation).
• Synergy is when two cytokines enhance each other's effect (e.g., IL-4 + IL-5 induce B cell class switching to IgE).
• Antagonism is when one cytokine inhibits another( e.g., IFN-γ blocks IL-4-induced IgE production).
• Cascade Induction is when one cytokine stimulates others (e.g., TNF-α induces IL-6 production).
• IL-4 and IL-5 work together to promote IgE antibody production in allergies

Cytokine Functional Categories

• The functional categories for Cytokines includes Mediators and regulators of innate immunity
• Mediators and regulators of adaptive immunity; and stimulators of haematopoiesis.
• Mediators and regulators of are produced by activated macrophages and NK cells in response to microbial infection, and act mainly on endothelial cells and leukocytes
• They include IL-2, IL-4, IL-5, IL-13, INF, TNF-α and TNF-β:
• Mediators and regulators of adaptive immunity is produced mainly by T lymphocytes in response to SPECIFIC recognition of foreign antigen Stimulate growth and differentiation of leukocytes

Biological Effects of Cytokine Stimulation

• Biological effects of cytokine stimulation include differentiation, proliferation, and activation of the target cell.
• Interleukins IL-2, IL-4, and IL-7 drive T cell proliferation in response to infections.

Interferons

• Interferons (IFNs) are proteins released by host cells in response to pathogens like viruses, bacteria, parasites, or tumor cells.
• Interferons are named for their ability to "interfere" with viral replication within host cells.
• IFNs can activate immune cells like natural killer cells and macrophages, up-regulating antigen presentation to T lymphocytes, and causing symptoms like aching muscles and fever during infection.

Key Interleukins & Functions

• IL-2 is for T cell proliferation and is used in cancer immunotherapy.
• IL-4 activates B cells and induces IgE switching during allergic reactions, exhibiting multiple effects (pleiotropy).
• IL-6 mediates the acute-phase response and is associated with fever & chronic inflammation.
• IL-8 has neutrophil chemotaxis, and recruits neutrophils to infection.
• TNF-α is an inflammatory response and causes sepsis, and rheumatoid arthritis
• INF-γ activates macrophages and is an antiviral response (antagonism).
• TGF-β suppresses inflammation, promotes wound healing, and immune regulation.

IL-8 & Chemotaxis

• IL-8 is a neutrophil chemotactic factor with two primary functions: inducing chemotaxis in target cells, causing them to migrate toward the site of infection, and stimulating phagocytosis once they have arrived.

Cytokine Storms & Disease

• A cytokine storm is an uncontrolled inflammation common in viral infections like COVID-19, flu, and sepsis.
• It leads to multi-organ failure & death.
• Key cytokines in a cytokine storm are IL-1, IL-6, TNF-α, and IFN-γ.
• A COVID-19 cytokine storm causes lung damage and severe inflammation.

Case Study: IL-8 in COVID-19 Treatment

• IL-8 is a key chemokine for neutrophil recruitment, but COVID-19 patients have excessive IL-8, leading to severe lung inflammation.
• Blocking IL-8 (BMS-986253) reduces inflammation & neutrophil activation, improving recovery in COVID-19 patients.
• Interleukin-8 (IL-8) is a potent chemotactic cytokine implicated in the pathogenesis of a number of inflammatory diseases.
• Blocking IL-8 (BMS-986253) reduces inflammation & neutrophil activation.

Key Takeaways On Cytokines

• Cytokines regulate immune responses & inflammation.
• Different cytokines have pleiotropic, redundant, and synergistic effects.
• IL-2, IL-4, IL-6, IL-8, TNF-α, and INF-γ play key roles in immunity.
• Cytokine storms can cause severe disease, but targeted therapies can help.

Case Scenario: IL-2 and Cancer Therapy

• Patient: Ellie, 55 years old, is being treated for advanced kidney cancer with Aldesleukin (IL-2 therapy).
• Aldesleukin is a recombinant IL-2 drug used for cancer immunotherapy, which enhances lymphocyte mitogenesis, cytotoxic T cell activity, and natural killer (NK) cell activation, and IFN-y production.
• IL-2 therapy boosts immune attack on tumor cells.

Inflammatory Cytokines - Definition

• Inflammation is mediated by a variety of soluble factors, including a group of secreted polypeptides known as cytokines.
• Inflammatory cytokines includes two groups: acute inflammation and chronic inflammation
• Inflammation is the response of tissue to injury.
• Inflammation is characterized in the acute phase by increased blood flow and vascular permeability and accumulation of fluid and leukocytes, and inflammatory mediators such as cytokines

Inflammatory Cytokines: Definition & Function

• Inflammation is mediated by cytokines released in response to injury or infection.
• Divided into two phases: acute inflammation (immediate response in hours or days) and chronic inflammation (prolonged immune activation in months or years).
• Acute inflammation features increased blood flow via vasodilation, increased vascular permeability, fluid & immune cell infiltration, and accumulation of leukocytes like neutrophils and macrophages.
• Cytokines known to mediate acute inflammatory reactions: IL-1, TNF-a, IL-6, IL-11, IL-8 and other chemokines, G-CSF, and GM-CSF.
• Cytokines are also known to mediate chronic inflammatory processes cannon divided into
  • Those participating in humoral inflammation, such as IL-3, IL-4, IL-5, IL-6, IL-7, IL-9, IL-10, IL-13, and transforming growth factor-b (TGF-b), -Those contributing to cellular inflammation such as IL-1, IL-2, IL-3, IL-4, IL-7, IL-9, IL-10, IL-12, interferons (IFNs), IFN-g inducing factor (IGIF), TGF-b, and TNF-a and -b.

Key Inflammatory Cytokines

Acute Inflammatory Cytokines

• Are cytokines produced by macrophages, neutrophils, and endothelial cells.
• They trigger fever, inflammation, and immune cell recruitment.
• IL-1: Fever, T cell activation, vascular permeability.
• TNF-a causes fever, inflammation, apoptosis, neutrophil activation.
• IL-6: mediates the acute-phase protein production, and causes fever
• IL-8 causes Neutrophil recruitment (chemotaxis)
• TNF-a is a major target in autoimmune disease

Chronic Inflammatory Cytokines

• They are due to Sustained immune activation which leads to tissue damage and is mediated by autoimmune diseases.
• IL-3, IL-4, IL-5 Promote antibody production B cell response
• IL-6, IL-7: Promote T and B cell survival
• IL-10 suppresses excessive inflammation
• IFN-Y activates macrophages, enhances antigen presentation
• IL-6 plays a key role in rheumatoid arthritis.

Proinflammatory Cytokines

• Play an important role in immune defense and healing by fighting infections by helping recruit immune cells to attack pathogens, tissue repair helps clear damaged cells and initiates healing system to help respond to threats:
• A proinflammatory cytokine is a cytokine which promotes systemic inflammation.
• These include Interleukin (IL)-1 and tumor necrosis factor (TNF) alpha and promote inflammation.
• Produced from immune cells like helper T cells (Th) and macrophages promote inflammation.
• Therapeutic strategies for reducing IL-1 and TNF activities involve neutralizing antibodies, soluble receptors, receptor antagonists, and inhibitors of proteases.
• Blocking IL-1 or TNF has been highly successful in patients with rheumatoid arthritis inflammatory bowel disease and graft-vs-host disease

Anti-Inflammatory Cytokines

• Are immunoregulatory molecules that control the proinflammatory cytokine response by acting in concert with specific cytokine inhibitors and soluble cytokine receptors to regulate the human immune response.
• Major anti-inflammatory cytokines include interleukin (IL)-1 receptor antagonist, IL-10, IL-11, and IL-13, but also IL-4, IL-6.
• It is critical that cytokine action is regulated to avoid inappropriate responses by transient production and short half-life
• Dysregulation of TNF-a leads to rheumatoid arthritis.

Anti-Inflammatory Cytokines Role

• Regulate and suppress immune activation to prevent tissue damage.
• IL-10 suppress macrophage activation and inhibits IL-1 & TNF-α
• TGF-β has its T cell activation and promote tissue repair
• IL-4, IL-13 Downregulation of inflammation will have lead to enhancement of wound healing
• IL-10 deficiency leads to uncontrolled inflammation (

Cytokine Regulation

• Cytokine activation is tightly controlled to prevent overactivation.
• Cytokine action is regulated by transient production only in response to either antigen or potent inflammatory stimuli -Short half-life of cytokines in extracellular fluids and compartments, restricted receptor expression profiles on the surface of both activated and unactivated target cells.
• Examples of cytokine dysregulation can lead to pathologic disease

Therapeutic Uses Of Cytokine Blocking Antibodies

• Cytokine andibodies treats autoimmune diseases and transplants
• Anti TNF-a treats Rheumatoid Arthritis
• Anti-II-2R helps with Graft rejection
• Anti-Il-6 antibodies Rheumatoid arthritis, Covid-19
• Used for prevention of transplant rejections and treat RA disorders

Cytokine Based Drugs

• Stimulates the immune response by aiding in Erythropoietin (EPO), used to treat anaemia, and Granulocyte colony-stimulating factor (G-CSF), used to treat neutropenia in cancer patients to stimulate the immune resposne
• Interferon alpha (INF-a), used to treat hepatitis C and multiple sclerosis and Interferon beta (INF-b), used to treat multiple sclerosis
• They stimulates the immune sysem for healing

Chronic Inflammatory Disease

• Chronic inflammatory disease is characterized by persistent inflammation.
• Patients develop this disease where the immune system has an reaction to something it has been exposed to.
• It can can increase damage in tissues such as celiac disease, vasculitis, lupus, chronic obstructive pulmonary disease (COPD), irritable bowel disease, atherosclerosis, arthritis, and psoriasis.
• Several cytokines play key roles in mediating chronic inflammatory reactions, namely IL3, IL6, TNFẞ, IL4, IL5, IL7, IL9, IL10, IL13, IL14, IFN to regulate the tissue

Cytokine Functions in Diseases

• An uncontrolled Cytokine Storm is from overproduction of inflammatory cytokines, common in severe infections like COVID-19 or Sepsis.
• Key Cytokines to the storm include IL-1,1L-6, INFa or IFNy
• Neutrophil infiltration into inflammatory sites is one of the hallmarks of acute inflammation which can trigger additional events

Aldesleukin Case Scenario

• Aldesleukin is very similar to the cytokine produced by cells called interleukin-2 (IL-2) which enhances our immunity.
• It is is part of the immune system stimulates growth and differentiation of T cell response that works on the body. Induction in enhancement of lymphocyte cell
• Interferon gamma production