Cytokines: Introduction to Intercellular Signaling in Immunology
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Cytokines: Introduction to Intercellular Signaling in Immunology

Learn about the complex networks involved in immunology where different cell types communicate through intercellular signals. Explore the two general ways of signal transmission: volume transmission and contact-dependent signaling.

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Questions and Answers

Which type of effect is described when cytokines bind to receptors on the cell that produced them?

Autocrine effect

In the context of cytokines, what is a paracrine effect?

Binding only to receptors on nearby cells

Which molecules act through toll-like receptors and trigger cytokine release?

PAMPs

What are the most important pathways that trigger cytokine release?

<p>Combination of antigens with T and B cell receptors</p> Signup and view all the answers

Which type of effect do cytokines have when they spread throughout the body and affect target cells in distant locations?

<p>Endocrine effect</p> Signup and view all the answers

What distinguishes cytokines from hormones in terms of their effects?

<p>Cytokines have autocrine or paracrine effects, while hormones have endocrine effects.</p> Signup and view all the answers

Which term describes the ability of a single cytokine to act on many different target cell types?

<p>Pleiotropy</p> Signup and view all the answers

In cytokine functions, what does the term 'redundancy' refer to?

<p>Multiple cytokines acting on a single target cell</p> Signup and view all the answers

What is the process called when some cytokines work best when paired with other cytokines?

<p>Synergy</p> Signup and view all the answers

Which statement best describes the impact of cytokines binding to receptors on target cells?

<p>They affect cell behavior.</p> Signup and view all the answers

How do cytokines differ from conventional hormones?

<p>Cytokines affect multiple cell types, while hormones affect a single target cell type.</p> Signup and view all the answers

Which type of transmission involves a mediator molecule diffusing through the extracellular fluid to the receiving cell?

<p>Volume transmission</p> Signup and view all the answers

What are the most important molecular mediators known as cytokines?

<p>Leukins, monokins, prostaglandins, and interferons</p> Signup and view all the answers

Which of the following is NOT a cytokine?

<p>Prostaglandin</p> Signup and view all the answers

How do cells of the immune system communicate among each other using cytokines?

<p>By releasing multiple different proteins to control immune responses</p> Signup and view all the answers

What is the main difference between volume transmission and network transmission of intercellular signals?

<p>Volume transmission involves mediator molecules diffusing, while network transmission involves direct cell contact.</p> Signup and view all the answers

Which of the following cytokines is a chemokine that acts on the brain to cause a fever?

<p>CCL3</p> Signup and view all the answers

Which of the following is NOT a characteristic of cytokines?

<p>Long-lived proteins</p> Signup and view all the answers

Which of the following is NOT a type of interferon?

<p>IFN-δ</p> Signup and view all the answers

Which of the following cytokines is primarily produced by macrophages and T cells?

<p>TNFα</p> Signup and view all the answers

Which of the following is NOT true about interleukins?

<p>They are primarily involved in antiviral activity</p> Signup and view all the answers

Which of the following cytokines is primarily involved in the maintenance of pregnancy?

<p>IFN-α</p> Signup and view all the answers

Which cytokine plays a critical role in inflammation and is also involved in fever, hematopoiesis, appetite control and acquired immunity?

<p>IL-1</p> Signup and view all the answers

Which cytokine is produced not only by activated macrophages but also by T and B cells, mast cells, vascular endothelial cells, fibroblasts, and keratinocytes?

<p>IL-6</p> Signup and view all the answers

Which cytokine is produced by TNF-α and IL-12 synergistically and promotes IFN-γ production?

<p>IFN-γ</p> Signup and view all the answers

Which cytokine is produced by activated Th2 cells, mast cells and eosinophils and controls eosinophil production?

<p>IL-5</p> Signup and view all the answers

Which cytokine is an immunosuppressive and anti-inflammatory cytokine that regulates inflammation, as well as T cell, NK cell, and macrophage function?

<p>IL-10</p> Signup and view all the answers

Which cytokine is produced by T cells, B cells, NK cells, and mast cells and acts on B cells, T cells, macrophages, and mast cells, stimulating the growth and differentiation of B cells?

<p>IL-4</p> Signup and view all the answers

Which cytokine is produced by T cells, B cells, NK cells, and mast cells and acts on B cells, T cells, macrophages, and mast cells, stimulating the growth and differentiation of B cells?

<p>IL-4</p> Signup and view all the answers

Which cytokine is produced by Th1 cells and is required for the final maturation of B cells into plasma cells?

<p>IL-6</p> Signup and view all the answers

Which cytokine is produced by Th2 cells and is a potent stimulator of innate immunity?

<p>IFN-γ</p> Signup and view all the answers

Which cytokine is produced by Th2 cells and is a stem cell growth factor produced only by Th2 cells?

<p>IL-9</p> Signup and view all the answers

What is one of the distinguishing characteristics of cytokines?

<p>Can have overlapping biological functions</p> Signup and view all the answers

Which statement best describes the nomenclature of interleukins?

<p>Heterogeneous mixture with little in common except their name</p> Signup and view all the answers

Which type of interferons primarily have antiviral activity?

<p>Type I interferons</p> Signup and view all the answers

What do type III interferons, such as IFN-λ, primarily possess?

<p>Immunoregulatory role</p> Signup and view all the answers

Which cells secrete TNFs according to the text?

<p>Macrophages and T cells</p> Signup and view all the answers

What is the primary function of TNF-α?

<p>Immune regulation</p> Signup and view all the answers

Which of the following cytokines is NOT a member of the TNF superfamily?

<p>CXCL8</p> Signup and view all the answers

What is the function of chemokines in the immune system?

<p>Leukocyte chemotaxis</p> Signup and view all the answers

Which type of cytokines are secreted by monocytes-macrophages?

<p>Monokines</p> Signup and view all the answers

What is the primary function of interleukins in the immune system?

<p>Regulating interactions between lymphocytes and leucocytes</p> Signup and view all the answers

What is the primary difference between volume transmission and network transmission of intercellular signals?

<p>Volume transmission involves diffusion of a mediator molecule, while network transmission involves direct contact between two cells.</p> Signup and view all the answers

How do cytokines differ from conventional hormones regarding their target cell types?

<p>Cytokines can affect many different cell types, while conventional hormones tend to affect a single target cell type.</p> Signup and view all the answers

Which type of cells secrete multiple cytokines simultaneously?

<p>Macrophages</p> Signup and view all the answers

What sets cytokines apart from conventional hormones in their secretion by immune system cells?

<p>Immune system cells secrete a single cytokine at a time, unlike conventional hormones.</p> Signup and view all the answers

Which of the following is NOT a type of cytokine mentioned as an important molecular mediator?

<p>Leptins</p> Signup and view all the answers

What characterizes the direct contact method of network transmission among cells?

<p>Two cells use complementary receptors to transmit signals to each other.</p> Signup and view all the answers

What is the term that describes the ability of many different cytokines to act on a single target cell?

<p>Redundancy</p> Signup and view all the answers

Which of the following is NOT a characteristic of cytokines?

<p>Endocrine effects</p> Signup and view all the answers

What term describes the ability of a single cytokine to act on many different target cell types, inducing different responses in each one?

<p>Pleiotropy</p> Signup and view all the answers

What is the process called when some cytokines work best when paired with other cytokines?

<p>Synergy</p> Signup and view all the answers

Which cytokine is produced by Th2 cells and is a potent stimulator of innate immunity?

<p>IL-4</p> Signup and view all the answers

Which of the following is NOT a pathway that triggers cytokine release?

<p>The combination of antigens with Fc receptors on T and B cells</p> Signup and view all the answers

Which of the following is NOT a type of cytokine effect?

<p>Intracrine effect</p> Signup and view all the answers

Which of the following does NOT act through toll-like receptors and trigger cytokine release?

<p>Toll-like receptors (TLRs)</p> Signup and view all the answers

Which of the following is NOT a function of cytokines?

<p>They bind to receptors on the nucleus of the cell</p> Signup and view all the answers

Which of the following is NOT a type of cell that produces cytokines?

<p>Nerve cells</p> Signup and view all the answers

Study Notes

Cytokines Introduction

  • Cytokines are molecular mediators that control immune responses by communicating among cells
  • The immune system forms complex networks involving many different cell types, each sending and receiving multiple messages from many different sources
  • Intercellular signals are transmitted in two general ways: volume transmission and network transmission

Cytokine Functions

  • Cytokines affect cell behavior, inducing cell division, differentiation, or stimulating the production of new proteins
  • Cytokines can inhibit cell division, differentiation, or new protein synthesis
  • Most cytokines act on many different target cell types, inducing different responses in each one (pleiotropy)
  • Many different cytokines may act on a single target, a feature known as redundancy
  • Cytokines can work in synergy with other cytokines to produce an effect

Cytokine Nomenclature

  • The nomenclature and classification of cytokines is not based on any systematic relationship among these proteins
  • Cytokines were originally named after their cell of origin or the bioassay used to identify them
  • Interleukins are cytokines that mediate signaling between lymphocytes and other leukocytes
  • There are 39 different numbered interleukins, each with different functions
  • Interferons are cytokines produced in response to virus infection or immune stimulation and have antiviral activity

Properties of Cytokines

  • Cytokines are short-lived proteins
  • Cytokines have highly diverse structures and receptors
  • Cytokines can act locally and/or systemically
  • Cytokines are pleiotropic, affecting many different cells
  • Cytokines are redundant, exhibiting biologically overlapping functions
  • Cytokines are carefully regulated and can be toxic in high doses

Cytokines Produced by Macrophages and Dendritic Cells

  • Macrophages produce IL-1, IL-6, IL-12, IL-18, and TNF-α
  • IL-1 plays a critical role in inflammation, fever, hematopoiesis, appetite control, and acquired immunity
  • IL-6 is produced by activated macrophages, T cells, B cells, mast cells, vascular endothelial cells, fibroblasts, and keratinocytes
  • IL-12 promotes Th1 cell activity and enhances T and NK cell proliferation and cytotoxicity
  • IL-18 acts on Th1 cells to promote the production of IFN-γ, IFN-α, IL-1, and several chemokines
  • TNF-α is a potent pro-inflammatory molecule that enhances the expression of adhesive molecules, promotes fibroblast proliferation and collagen production

Cytokines Produced by T Cells

  • Th1 cells produce IL-2, TNF-γ, and IFN-γ
  • IL-2 activates helper and cytotoxic T cells and NK cells
  • IFN-γ stimulates B cell production of IgG and enhances T cell production of MHC class I molecules
  • Th2 cells produce IL-4, IL-5, IL-9, IL-10, and IL-13
  • IL-4 acts on B cells, T cells, macrophages, and mast cells, stimulating the growth and differentiation of B cells
  • IL-5 controls eosinophil production and stimulates the growth and differentiation of eosinophils
  • IL-10 is an immunosuppressive and anti-inflammatory cytokine that regulates inflammation and T cell, NK cell, and macrophage function
  • IL-13 has similar effects to IL-4 on B cells and macrophages, stimulating their proliferation and increasing immunoglobulin secretion.

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