Week 2: Cytokines, Chemokines, & Cell Signaling Fusion Session - January 2024 PDF

1/24/24, 1:03 PM  Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024                Fusion sessions are online learning activities followed by a live session where you will translate the content int...

1/24/24, 1:03 PM  Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024                Fusion sessions are online learning activities followed by a live session where you will translate the content into practice. These require completing learning content in Canvas before attending live sessions. To encourage preparation, attendance, and participation, recordings of fusion sessions will not be posted; prepare accordingly so that you can fully participate. Remember: Learning from written materials is a critical professional and personal skill that RUSM is helping you develop through these sessions. Top https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 1/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 1. Work through the content on this page. 2. Contact faculty via email or office hours if you have questions about content to ensure you are prepared for the session. 3. Take the quiz. (You have three attempts.) 4. Attend and participate in the live session. 5. Take the quiz again. 6. Study missed content. 7. Take the quiz for the final attempt.  Cytokines are the workhorses of the immune system. Cytokines direct the development of leukocytes, their differentiation into different subsets, their activation, their functions, as well as their regulation. In fact, nowadays, medicine in immunology is all about the control of immunological processes, whether considering normal immunological processes, pathophysiological processes (and not just immunopathology), or the treatment of many conditions including, but not limited to, inflammatory diseases, infectious diseases, autoimmune diseases, asthma, obesity, type 2 diabetes, and transplant rejection. In fact, there are already many approved pharmacological agents targeting cytokine and cytokine signaling, as well as many more at various stages of development (from basic laboratory research to various stages of clinical trials). In this section of the course, you will be introduced to the basics of cytokines, chemokines, as well as the pathways through which they primarily signal. By the end of this session, you will be able to meet the following learning objectives: 1. Define cytokines (and chemokines), describe their general function(s), and discuss how Top their expression is regulated. 2. Define autocrine, paracrine, juxtacrine, and endocrine signaling, and describe examples of each. https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 2/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 3. List the major classes, by function, of cytokines (bolded & highlighted); list examples of cytokines in each class. 4. List the classes of chemokines; list examples of CC and CXC chemokines (bolded & highlighted). 5. In relation to cytokines, define the concepts of pleiotropism, redundancy, additivity, synergy, and antagonism, and identify these cytokine properties when provided with examples. 6. List the cytokine and chemokine receptor families and provide examples of their respective ligands. 7. Describe the IL-2, IL-4, IL-7, IL-15, and IL-21 cytokine receptors and list the JAK associated with each receptor chain. 8. Describe the signaling cascades for the following receptors: a. Type I and Type II cytokine receptors; b. TNF receptors; c. IL-1 receptors; d. Seven transmembrane G-protein-coupled receptors. Click the tab below to learn more about the relevant USMLE content. Topics covered in this session are highlighted. Development of cells of the adaptive immune response, including positive and negative selection during immune development Structure, production, and function granulocytes, natural killer cells, macrophages, mast cells, dendritic cells, cell receptors (e.g., complement receptors and Toll-like receptors), cytokines, chemokines T lymphocytes, including T-lymphocyte receptors, accessory molecules (e.g., CD3, CD4, CD8, B7), cell activation and proliferation, cytotoxic T lymphocytes, and memory T lymphocytes B lymphocytes and plasma cells, including B-lymphocyte receptors, immunoglobulins, cell activation and proliferation, including development of antibodies and memory B lymphocytes host defense mechanisms, host Topbarriers to infection, mucosal immunity (e.g., gutassociated lymphoid tissue and bronchus-associated lymphoid tissue), anatomical locations of T and B lymphocytes Cellular basis of the immune response and immunologic mediators https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 3/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 antigen processing and presentation in the context of MHC I and MHC II molecules (e.g., TAP, beta-2 microglobulin), intracellular pathways, mechanisms by which MHC is expressed on the surface; including distribution of MHC I and MHC II on different cells, mechanisms of MHC I and MHC II deficiencies, and the genetics of MHC regulation of the adaptive immune response (e.g., peripheral tolerance, anergy, regulatory T lymphocytes, termination of immune response, and B-T lymphocyte interactions) activation, function, and molecular biology of complement (e.g., anaphylatoxins) functional and molecular biology of cytokines (e.g., IL 1-15) Basis of immunologic diagnostics (e.g., antigen-antibody reactions used for diagnostic purposes, ELISA, immunoblotting, antigen-antibody changes over time, ABO typing) Principles of immunologic protection vaccine production and mechanisms of vaccine action biologically active antibodies (e.g., monoclonal antibodies, polyclonal antibodies including IVIG, VZIG, rabies immunoglobulin) Effect of age on the function of components of the immune system Abbas, A. K., Lichtman, A. H., & Pillai, S. (2022). Cellular and Molecular Immunology (10th ed.). Elsevier. Delves, P. J., Martin, S. J., Burton, D. R., & Roitt, I. M. (2011). Roitt's essential immunology (12th ed.). Wiley-Blackwell. Murphy, K., Travers, P., & Walport, M. (2008). Janeway's immunobiology (7th ed.). Garland Science. Sompeyrac, L. (2019). How the immune system works (6th ed.). Wiley-Blackwell. Top Dinarello, C. A. (2007). Historical review of cytokines. European Journal of Immunology, 37(Supp 1), S34-S45. https://doi.org/10.1002/eji.200737772 https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 4/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024  Note: It is hard to learn cytokines, and students often struggle with this subject matter. Based on student feedback over the years, below is some advice on how best to learn cytokines. Given the sheer number of cytokines you need to learn, and that (1) many cytokines overlap in their functions and (2) most cytokines perform multiple functions, there is no point in memorizing each cytokine you need to learn about and their respective functions; this is because their function(s) is(are) context-specific. For example, tumor necrosis factor alpha (TNF-α) can perform many different functions: at the cellular level, TNF-α (in conjunction with other cytokines or other stimuli) can help activate phagocytic cells; at a site of injury, TNF-α (1) stimulates the expression of adhesion molecules on the luminal surface of endothelial cells, (2) is an important mediator of vasodilation, (3) disrupts endothelial adherence junctions to promote vascular leakage for the purpose acute-phase reactant and leukocyte infiltration in the affected tissue (which leads to swelling, syn. edema), and (4) is chemotactic for leukocytes; in the brain (hypothalamus), TNF-α is pyrogenic (i.e., it induces fever via prostaglandin stimulation); systemically, TNF-α, via hormonal stimulation, induces energy production through carbohydrate, protein, and fatty acid catabolism, sometimes yielding anorexia and cachexia (wasting syndrome seen in cancer & AIDS for example); again, at the cellular level, TNF-α can trigger apoptosis (e.g., tumor cell death); and these are but the main functions of TNF-α…. With all of this in mind, here is some advice for you: For the time being, classify the different cytokines you need to learn according to their general function(s); there is a table in the Study Activity section to enable you to do just that. This exercise will help you see that, despite the vast number of cytokine functions, they can generally be somewhat segregated according to the main type(s) of response(s) they are involved in; you will find there is little overlap in these functional clusters, and this will help you narrow down the cytokines involved in more specific contexts and home in on their relevant function(s) in these contexts. As we progress through immunological processes, learn the specific functions of the cytokines within these specific contexts. It will make your learning more gradual and more Toprelevant. You will also find that we will often refer to the same groups of cytokines. This repetition, as we go along, will be helpful in consolidating your knowledge of cytokines. To illustrate this point, imagine having to answer the following question: https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 5/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 A 73-year-old man with a history of COPD, myocardial infarction, and congestive heart failure is admitted to the hospital. On physical examination, the following are noted: temperature 39.4 °C (102.9 °F), pulse 136, respiratory rate 25, blood pressure 98/52 mmHg, SaO2 0.90, and the patient is lethargic and diaphoretic. His serum lactate is 3.3 mmol/L, total WBC are 18,000/mm3, and the prothrombin time is prolonged; further relevant laboratory investigation reveals a presepsin level of 961 ng/L. What pathophysiological process accounts for most of the signs seen in this patient?  Tissue recruitment of mononuclear phagocytes  Release of acute-phase reactants by the liver  Leukocyte apoptosis  Fever generation  Protein catabolism  Vascular alterations  Check A 73-year-old man with a history of COPD, myocardial infarction, and congestive heart failure is admitted to the hospital. On physical examination, the following are noted: temperature 39.4 °C (102.9 °F), pulse 136, respiratory rate 25, blood pressure 98/52 mmHg, SaO2 0.90, and the patient is lethargic and diaphoretic. His serum lactate is 3.3 mmol/L, total WBC are 18,000/mm3, and the prothrombin time is prolonged; further relevant laboratory investigation reveals a presepsin level of 961 ng/L. What pathophysiological process accounts for most of the signs seen in this patient? Release of acute-phase reactants by the liver Protein catabolism Leukocyte apoptosis Tissue recruitment of mononuclear phagocytes Fever generation Vascular alterations (Correct answer) Once you have learned about sepsis, it will become obvious that the key mediator in sepsis Top pathophysiology is, by far, TNF-α. Although all the above answer options are physiological effects of TNF-α, knowing the pathophysiology of sepsis will allow you to recognize that “vascular alterations” is clearly the best answer for this particular scenario. https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 6/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 Hopefully, your learning of cytokines will be made a little easier with this understanding.  Cytokines are the primary communication molecules used within the immune system and between the immune system and other body systems; they are the molecules through which leukocytes communicate with one another and with other cells of the body; the term InterLeukin (IL) is derived from their main function; interleukin numbering as based on the chronological order of their discovery. Cytokines participate in many types of immune reactions, from inflammation and tissue repair to the termination of immune responses and every process in between. Generally speaking, cytokines are referred to as proinflammatory (involved in inflammatory reactions) or antiinflammatory (prevent or decrease inflammation). Cytokines are proteins, and they mediate their actions through ligand/receptor interactions; cytokine engagement of its receptor results in the expression of genes that are responsive to this cytokine (biological response) by way of intracellular signaling pathways. Generally speaking, cytokines upregulate their own production and that of functionally related cytokines, as well as that of their receptors, in an effort to amplify the response (fast response times are important when dealing with potentially life-threatening infections). Finally, although most cytokines are soluble, some cytokines also can be membrane-bound (mb), e.g. FasL (CD95L or CD178), CD40L (CD154), mbIL-1b, mbIL-15, mbM-CSF, mbFlt3 ligand, mbTNF-α, mbLTα, membrane-bound fractalkine, mbTGF-β, and mbIFN-γ, etc. Cytokines are very potent molecules, and for this reason, their expression needs to be tightly regulated. Cytokines normally act over a short period of time and at low concentrations; low and ephemeral expression of cytokines (e.g., due to short cytokine mRNA half-life, rapid cytokine turn-over, etc.) is an effective means of avoiding 1. excessive responses that can Topbe life-threatening (e.g., cytokine storms seen in sepsis & toxic shock, etc.) and 2. chronic inflammation and unnecessary tissue damage (inflammation is generally sustained as long as there is enough antigen present to maintain cytokine stimulation, a https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 7/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 concept we will further develop in the Antigen Presentation and T Lymphocyte Biology lecture…). Finally, many cytokines act to regulate the expression of other cytokines (e.g.,TH1 cytokines inhibit the expression of TH2 cytokines and vice versa, or anti-inflammatory cytokines regulate the expression of pro-inflammatory cytokines, again to avoid excessive cytokine expression). All cytokines are expressed in soluble form.  True  False  Check  Question 1 All cytokines are expressed in soluble form: True False (Correct answer) Explanation: Although most cytokines are expressed in soluble form, many are membraneTop bound, e.g. CD95L. Question 2 To elicit a cellular response, cytokines must engage a cell receptor: https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 8/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 True (Correct answer) False Question 3 Because of their potency, cytokines are tightly regulated: True (Correct answer) False Cytokines also generally act in an autocrine, juxtacrine, or paracrine fashion, but can sometimes act in an endocrine fashion as well. Examples of autocrine signaling include IL-2 self-stimulation of expanding T lymphocytes following their activation, or macrophage TNF-α self-stimulation following detection of a microbial invader, e.g. as a result of Toll-Like Receptor (TLR) signaling (so autocrine signaling occurs when the target cell is the same as the cell releasing the cytokine(s) – these examples will be further developed in later activities, e.g. innate immunity, inflammation, as well as T lymphocyte biology). Furthermore, the cytokines mentioned in the previous examples (IL-2 & TNF-α) can also act on neighboring cells in what is referred to as paracrine signaling. Juxtacrine signaling involves the interaction between a membrane-bound cytokine and its cognate receptor on the surface of its target cell and thus requires direct cell-cell contact; examples of juxtacrine signaling include CD178/CD95 and CD154/CD40 interactions. Additionally, some cytokines can act at a distance, on other tissues, e.g. when IL-1β released at the site of infection reaches the hypothalamus to reset the body’s temperature and induce fever, or when IL-6 stimulates the liver to induce the production of acute-phase reactants at the start of an inflammatory process; in these latter examples, cytokines act in an endocrine fashion (again, these examples will be further developed later, e.g. inflammation). Finally, different cytokines are often expressed together and complement each other’s work, and the effects of cytokines generally result in cascades that radiate into physiological responses that act as a network rather than linearly. Watch this video about Autocrine/paracrine/endocrine signaling (https://www.youtube.com/watch?v=QL8yAtQXwuo%20) . Top https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 9/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 Cytokines are synthesized de novo; they are not performed; their expression needs to be stimulated by one or several signals (usually pathogen-recognition receptors, or PRRs, e.g., TLRs, and/or cytokines) that lead(s) to cytokine gene transcription (mRNA expression or synthesis), translation (protein synthesis), and secretion. Consequently, cytokines are not stored in cells; they are synthesized upon stimulation, and that is another level of cytokine regulation. The interaction between a membrane-bound cytokine and its receptor on a target cell is referred to as:  Endocrine signaling  Paracrine signaling  Juxtacrine signaling  Autocrine signaling  Check The interaction between a membrane-bound cytokine and its receptor on a target cell is referred to as: Paracrine signaling Autocrine signaling Juxtacrine signaling (Correct answer) Top Endocrine signaling https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 10/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 Different cell types can synthesize the same cytokine, and different cytokines can be expressed by discrete cell types, just as a particular cell type can synthesize different cytokines. Furthermore, some cytokines may exhibit several different functions, a property referred to as pleiotropism, and some cytokines may be limited to a single function; most cytokines are pleiotropic. Also, different cytokines may possess the same biological activity (redundancy) or overlap in their biological activity (partial redundancy); many cytokines are redundant in function (i.e., many cytokines overlap in their functions). Different cytokines may act 1. additively, (i.e., the combined effect of two or more cytokines is more or less equal to the sum of the effects of the cytokines taken separately), 2. synergistically, (i.e., the combined effect of two or more cytokines is much greater than the sum of the effects of the cytokines taken individually), or 3. antagonistically, (i.e., the effects of a cytokine inhibit the effects of the other). Finally, some cytokines are specialized in attracting cells, especially leukocytes: these cytokines are defined as chemokines. Chemokines are named based on the spacing of their first cysteine residues; there are four classes of chemokines: C, CC, CXC, and CX3C chemokines, with the X representing amino acids between the first two cysteine residues starting at the N-terminal end of their polypeptide chain; chemokines are named based on their family, followed by L (for ligand) and a number (e.g., CXCL8 which is the correct name for IL-8). Their receptors follow the same nomenclature rules, but with an R at the end to denote that it is a chemokine receptor. Finally, many chemokines are ligands for several chemokine receptors. For example, CXCL8 signals through CXCR1 and CXCR2. Top https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 11/35 1/24/24, 1:03 PM Week 2: Fusion Session | Workshop: Cytokines, Chemokines, & Cell Signaling: Hemtlgy Onclgy Infectn Imm - January 2024 When the combined effect two different cytokines is greater than the sum of their individual effect, the cytokines are said to act:  Redundantly  Synergistically  Additively  Antagonistically  Check When the combined effect two different cytokines is greater than the sum of their individual effect, the cytokines are said to act: Additively Antagonistically Redundantly Synergistically (Correct answer) For this term, you will need to know the cytokines that are bolded and highlighted. You will see the other ones (bolded) later. For a more exhaustive list of functions, cytokine-releasing cells, and target cells, refer to Appendix II of your required book (Cellular and Molecular Immunology). Also, some of the non-bolded cytokines and chemokines play important roles in diseases… Anyone remember SARS-CoV-2? Some of these are extremely important in some conditions, to name only Acute Respiratory Distress Syndrome. Top In addition to their roles in normal physiological processes and pathophysiology, several cytokines and their signaling are targets for many approved pharmacological https://rossmed.instructure.com/courses/3318/pages/week-2-fusion-session-%7C-workshop-cytokines-chemokines-and-cell-signaling 12/35