Inflammatory Cytokines and the Immune System

Case Scenario

• A 55-year-old named Ellie is being treated for advanced kidney cancer that has spread
• Her treatment includes a drug called Aledesleukin, which is based on interleukin 2 (IL-2)
• Aledesleukin is an immunotherapy drug with the brand name Proleukin

Inflammatory Cytokines - Definition

• Inflammation is mediated by soluble factors, including secreted polypeptides known as cytokines
• Inflammatory cytokines are divided into acute and chronic inflammation groups
• Inflammation is the response of tissue to injury
• Acute phase inflammation is characterized by increased blood flow, vascular permeability, accumulation of fluid and leukocytes, and inflammatory mediators like cytokines

Inflammatory Cytokines

• Cytokines mediate acute inflammatory reactions
• These include IL-1, TNF-a, IL-6, IL-11, IL-8, chemokines, G-CSF, and GM-CSF
• Cytokines mediate chronic inflammatory processes and can be divided into two groups
  • Those participating in humoral inflammation (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

Proinflammatory Cytokines

• Inflammatory abnormalities are a large group of disorders that underlie various human diseases
• Cytokines regulate host responses to infection, immune responses, inflammation, and trauma
• Proinflammatory cytokines promote systemic inflammation
• Examples of proinflammatory cytokines are IL-1 and TNF alpha, as well as Interleukin (IL)-1 and tumor necrosis factor (TNF)
• These are secreted from immune cells, like helper T cells (Th), macrophages, and other cells that promote inflammation
• Fever, inflammation, and tissue destruction are produced

Blocking Proinflammatory Cytokines

• Several strategies accomplish blocking the biological activities of IL-1 and TNF
  • Neutralizing antibodies
  • Soluble receptors
  • Receptor antagonists
  • Inhibitors of proteases that convert inactive precursors to active molecules
• This blocking has been highly successful in patients with rheumatoid arthritis, inflammatory bowel disease, and graft-vs-host disease

Anti-Inflammatory Cytokines

• They are immunoregulatory molecules that control the proinflammatory cytokine response
• Cytokines act with specific cytokine inhibitors and soluble cytokine receptors to regulate the human immune response
• Major anti-inflammatory cytokines include the interleukin (IL)-1 receptor antagonist, IL-10, IL-11, IL-13, IL-4 and IL-6
• Specific cytokine receptors for IL-1, tumor necrosis factor-alpha, and IL-18 also function as proinflammatory cytokine inhibitors

Cytokine Regulation

• Activation by cytokines occurs in an antigen-non-specific manner and must be regulated to avoid inappropriate responses
• Cytokine action is regulated by transient production, short half-life, and restricted receptor expression
  • Transient production 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
• Cytokine dysregulation can result in pathological disease such as the role of tumor necrosis factor alpha (TNFα) in the development of rheumatoid arthritis
• The effect of the cytokine dysregulation can be blockaded through administration of a recombinant soluble TNF-receptor or anti-TNF blocking antibody

Cytokines in Acute Inflammatory Disease

• Several cytokines play key roles in mediating acute inflammatory reactions, mainly IL-1, TNFα, IL-6, IL-11, IL-8, G-CSF, and GM-CSF

TNFα and Acute Inflammatory Disease

• Leukocyte migration from the peripheral blood to extravascular sites is a key feature of the inflammatory response
• TNFa is secreted by immune and parenchymal cells at inflammation sites and can promote immune cell extravasation by activating endothelial cells to express adhesion molecules for immune cells
• TNFa induces the expression of many other inflammatory cytokines and chemokines
• Both TNFα and IL-1 share several pro-inflammatory properties
• Like IL-1, TNFα can induce fever, either directly via stimulation of PGE2 synthesis or indirectly by inducing release of IL-1

IL1 and Acute Inflammatory Disease

• IL-1 family consists of IL-1α and IL-1β
• IL-1 are primarily produced by mononuclear phagocytes, fibroblasts, keratinocytes, and T and B lymphocytes
• Like TNFα, IL-1 is also a pro-inflammatory cytokine that plays a critical role in inflammation
• IL-1a and IL-1ẞ can trigger fever by enhancing prostaglandin E 2 (PGE2) synthesis by the vascular endothelium of the hypothalamus and can stimulate T cell proliferation
• IL-1 elicits the release of histamine from mast cells at the site of inflammation, which triggers early vasodilation and increase of vascular permeability

IL-8 and Acute Inflammatory Disease

• Neutrophil infiltration into inflammatory sites is one of the hallmarks of acute inflammation -Locally produced chemotactic factors mediate the sequence of events leading to the infiltration at inflammatory sites
• Administration of a neutralizing antibody to IL-8 prevents neutrophil-mediated tissue injury and infiltration in animal disease models
• Anti-IL-8 antibody effectively prevented two models very relevant to clinical situations
  • Endotoxemia-induced acute respiratory distress syndrome (ARDS)-like lung injury
  • Cerebral reperfusion injury

Cytokine Storm

• Cytokines produces symptoms of infection such as fever, inflammation, runny nose, and aches/pains
• Cytokine production can grow out of control
• Immune cells release cytokines that tell the body to produce more immune cells, which in turn release even more pro-inflammatory cytokines, a positive feedback loop that can lead to a “cytokine storm"
• A cytokine storm is an over-activation of immune cells and over-production of their activating compounds that damages organs, especially the lungs and kidneys, potentially leading to death
• Examples of cytokine storms include severe cases of the 1918 "Spanish Flu" pandemic and sepsis

Chronic Inflammatory Disease

• Chronic inflammatory disease is characterized by persistent inflammation
• Patients develop a chronic inflammatory disease because the immune system has an inappropriate response to something it has been exposed to
• Chronic inflammation causes considerable damage to the tissues of the body, leads to a progressive shift in the type of cells present at the site of inflammation and is characterized by simultaneous destruction and healing of the tissue from the inflammatory process
• Examples of inflammatory diseases that become chronic include celiac disease, vasculitis, lupus, chronic obstructive pulmonary disease (COPD), irritable bowel disease, atherosclerosis, arthritis, and psoriasis

Chronic Inflammatory Disease Continued

• Several cytokines play key roles in mediating chronic inflammatory reactions, namely IL3, IL6, TNFẞ, IL4, IL5, IL7, IL9, IL10, IL13, IL14, IFN

IL-6 and Chronic Inflammatory Disease

• IL6 is produced at the site of inflammation
• At the beginning of acute inflammation, IL-6 mediates the acute phase responses
• When its activity as a pro-inflammatory cytokine persists, acute inflammation turns into chronic inflammation
• In chronic inflammation, IL-6 has a detrimental role that favors mononuclear cell accumulation at the site of injury, through continuous MCP-1 secretion, angioproliferation, and anti-apoptotic functions on T cells
• Serum levels of IL-6 may increase, providing the basis for the amplification step of chronic inflammatory proliferation

Cytokine Inhibitor Drugs

• Three ways to reduce the number of cytokine producing cells
  • Decrease the number of cytokine producing cells: inhibit cytokine synthesis (e.g., methotrexate)
• Two ways without affecting viability of cells by inhibiting cytokine synthesis (e.g., glucocorticoids such as prednisone)
  • Anti-inflammatory or immunosuppressive effect by inhibiting interleukin-1, tumor necrosis factor, or interleukin-2
• Monoclonal antibody as cytokine (e.g., Infliximab)
  • Antibody directed against TNFa- tumor necrosis factor for autoimmune disorders

Therapeutic Uses of Cytokine Blocking Antibodies

• Anti-cytokine antibodies are used to treat autoimmune diseases and transplant rejection
  • Anti-TNF-a: treats Rheumatoid Arthritis
  • Anti-IL-2R: treats Graft rejection
  • Anti-Il-6 antibodies: treats Rheumatoid arthritis, Covid-19

Cytokine Based Drugs - Stimulate the Immune Response

• Erythropoietin (EPO) is used to treat anemia.
• Granulocyte colony-stimulating factor (G-CSF) is used to treat neutropenia in cancer patients.
• Interferon alpha (INF-a) is used to treat hepatitis C and multiple sclerosis.
• Interferon beta (INF-b) is used to treat multiple sclerosis.
• Interleukin 11 (IL-11) is used to treat thrombocytopenia in cancer.
• Interleukin 2 (IL-2), also known as Aldesleukin, is used to treat cancer.

Therapeutic Uses of Cytokines - Overview

• INT treatment of viral diseases and cancer
• IL-2, INF-g, TNF-a Enhance T cell activation in immunodeficiency
• II-2 T-cell proliferation Cancer
• GM-CSF induces increase in leukocyte blood count
• To restore leukocyte count after cytotoxic chemotherapy
• After bone marrow transplantation
• Correct AIDS-associated leukopenia

Case Scenario

• Ellie (55) is being treated for kidney cancer that has spread to another part of the body (advanced kidney cancer)
• Her treatment includes a drug based on interleukin 2 (IL-2) known as Aledesleukin
• Aldesleukin is an immunotherapy drug with the brand name Proleukin

Case Scenario

• Aldesleukin is similar to interleukin-2 (IL-2) produced by our cells
• Interleukin-2 is part of the immune system, secreted by T cells and stimulates growth and differentiation of T cell response
• Aldesleukin works by: induction, enhancement of lymphocyte mitogenesis, stimulation of long-term growth of human interleukin-2 dependent cell lines, enhancement of lymphocyte cytotoxicity, the induction of killer cell (lymphokine-activated (LAK) - and natural (NK)) activity and induction of interferon-gamma production

Mechanism of Action

• Aldesleukin (high-dose II-2) binds to the IL-2 receptor which leads to heterodimerization of the cytoplasmic domains of the IL-2R beta and gamma(c) chains, activation of the tyrosine kinase Jak3 and phosphorylation of tyrosine residues on the IL-2R beta chain
• These events led to the creation of an activated IL-2R receptor complex.
• IL-2R signaling triggers three distinct pathways
• These events stimulate growth and differentiation of II-2 dependent T cells