What is the general definition of a cytokine (or immunocytokine)?
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Soluble proteins and peptides that act as humoral regulators at nano- to picomolar concentrations.
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What is the general definition of a cytokine (or immunocytokine)?
Soluble proteins and peptides that act as humoral regulators at nano- to picomolar concentrations.
What term describes a cytokine's ability to show multiple biological activities by acting on more than one cell type?
Pleiotropy
In the context of cytokine activity, what term is used when multiple cytokines can perform the same function?
Redundancy
Which cytokine interaction occurs when two or more cytokines cooperate to produce an effect greater than their individual combined effects?
Synergy
What term describes the interaction where one cytokine works against the effects of another cytokine?
Antagonism
What are the four key structural and functional properties of cytokines?
How is the production of most cytokines usually regulated?
The expression is normally transient and can be regulated at all levels of gene expression (usually only produced by activated cells).
What are two examples of cytokines that are exceptions to the rule of not being stored inside cells?
TGF-(\beta) (Transforming growth factor beta) and PDGF (Platelet-derived growth factor).
What four mechanisms allow non-specific cytokines to act specifically on certain targets?
What is the term for cytokine action where the protein modulates the same cell that produced it?
Autocrine signaling.
What is the term for cytokine action where the protein modulates cells in its immediate surroundings?
Paracrine signaling.
What cytokine action involves modulation through cell membrane signaling requiring physical contact?
Juxtacrine signaling.
Which term refers to cytokines produced exclusively by leukocytes?
Interleukins (ILs)
Which term describes cytokines produced exclusively by monocytes?
Monokines
Which class of cytokines is specifically involved in antiviral responses?
Interferons (IFNs)
In the context of cytokine timing, what is the role of hierarchical order?
Early cytokines pre-activate cells so they can respond to later-acting cytokines.
What name is given to cytokines that support the growth of cells in semisolid media?
Colony Stimulating Factors (CSFs)
What is a common functional similarity between cytokines and growth factors?
Both act as cellular survival factors by preventing apoptosis.
How can cytokines be similar to classical hormones in their range of effect?
Both can behave as classical hormones acting at a systemic level (e.g., affecting inflammation, septic shock, acute phase reactions, and wound healing).
In terms of source, how do cytokines differ from classical hormones?
Hormones are produced in specialized glands, whereas cytokines have no single organ source.
How do hormones and cytokines compare in their typical modes of action?
Hormones typically act via endocrine signaling (systemic), while cytokines primarily act via autocrine or paracrine signaling.
How do cytokines and hormones differ in their half-lives?
Cytokines have a short half-life compared to the medium-to-long half-life of hormones.
What is the difference in molecular type between hormones and cytokines?
Hormones can be proteins, steroids, amino acid derivatives, or fatty acid derivatives, while cytokines are solely proteins.
Compare the production of cytokines and hormones.
Cytokines are produced by both immune and non-immune cells, whereas hormones are primarily produced by endocrine glands.
Into which two main functional categories are cytokines produced by helper T-cells classified?
Type-1 cytokines (produced by Th1 cells) and Type-2 cytokines (produced by Th2 cells).
What is the primary immunological role of Type-1 cytokines?
They help cellular immunity responses.
What is the primary role of Type-2 cytokines in the immune system?
They help B-cell development and antibody secretion.
What are four examples of Type-1 cytokines?
IL-2, IFN(\gamma), IL-18, and TNF-(\beta).
What are five examples of Type-2 cytokines?
IL-4, IL-5, IL-6, IL-10, and IL-13.
What are the six major families of cytokine receptors?
Which cytokine receptor family binds most immune and hematopoietin cytokines?
Class I cytokine receptor family (hematopoietin receptors).
What are several examples of short-chain cytokines?
IL-2, IL-3, IL-4, IL-5, IL-7, IL-9, IL-13, IL-15, GM-CSF, M-CSF, and SCF.
What are several examples of long-chain cytokines?
IL-6, IL-11, Erythropoietin, Thrombopoietin, and Leptin. (Also LIF, OSM, CNTF, CT-1, G-CSF).
What was the original name given to Interleukin-2 (IL-2)?
T-cell growth factor (TCGF).
Which cells are the main producers of Interleukin-2?
Mitogen-activated CD4+ T-lymphocytes. (Also transformed T/B cells, LAK, and NK cells).
What are three key actions of Interleukin-2 in the immune response?
What is a significant physiological side effect of IL-2 therapy in the brain?
IL-2 damages the blood-brain barrier and the integrity of brain vessel endothelium.
Why can IL-2 therapy lead to neuropsychiatric side effects such as fatigue and depression? (Mechanistic reason).
IL-2 does not have a saturable transport system across the blood-brain barrier.
Which cytokine is considered the major B-cell growth factor?
Interleukin-4 (IL-4).
What role does IL-4 play in immunoglobulin production?
It induces the class switch from IgG to IgE and inhibits IgM synthesis.
What effect does IL-4 have on B-cell surface molecules?
IL-4 induces expression of MHC Class II molecules on B-cells and increases cell surface expression of Fc(\epsilon)RII (CD23).
What cells are primary producers of Interleukin-4?
Activated CD4+ T-cells, NK cells, mast cells, and basophils.
Which type of cells produce Interleukin-7 (IL-7)?
Stromal cells (it is NOT a lymphokine).
What is the major role of Interleukin-7 in T-cell development?
Enhancing thymocyte growth, survival, and differentiation.
How does Interleukin-7 affect B-cell development?
IL-7 stimulates the proliferation of pre-B and pro-B cells but does NOT affect their differentiation or act on mature B-cells.
Which cells produce Interleukin-9 (IL-9), and which cell type does it primarily support?
Activated T-cells (supports Th clones but NOT CD8+ clones).
Compared to IL-2, what is distinctive about the timing of IL-9 synthesis?
Delayed production (suggests late/secondary signaling).
Which is the most recently identified Type I cytokine?
Interleukin-15 (IL-15).
What is the major immunological role of Interleukin-15?
NK cell development and cytolytic activity.
Which receptor chain is shared by the receptors for IL-2, IL-4, IL-7, IL-9, and IL-15?
The common gamma chain ((\gamma)c).
What clinical condition results from mutations in the common gamma chain ((\gamma)c)?
XSCID (X-linked severe combined immunodeficiency) or moderate XCID.
What is the result of mutations in Jak3?
An autosomal-recessive form of SCID.
Which Janus kinases (JAKs) interact with the receptors for cytokines that share the common gamma chain?
Jak1 and Jak3.
What are chemokines, and what is their primary size and function?
Small (8-10 kd), secreted, heparin-binding chemoattractant cytokines that promote leukocyte recruitment and activation.
What is the structural characteristic of the CC class of chemokines?
The first two cysteines are adjacent (e.g., MCP-1, RANTES).
What is the structural characteristic of the CXC class of chemokines?
The first two cysteines are not adjacent (separated by one amino acid) (e.g., IL-8).
What is unique about the C class of chemokines?
It has only 2 cysteines instead of the usual 4 (e.g., Lymphotactin).
What characterizes the CX3C (or CXXXC) class of chemokines?
It has 3 amino acids between the first two cysteines and a different N-terminal (e.g., Fractalkine/Neurotactin).
What is a key example of a CXC chemokine?
Interleukin-8 (IL-8).
What are several examples of CC chemokines?
MCP-1 to 4, MIP-1 (\alpha)/(\beta)/(\gamma), RANTES, and Eotaxin 1-3.
What is chemotaxis in the context of chemokine function?
The directed movement of cells along a chemical concentration gradient toward the area of highest concentration.
What internal cell changes do chemokines promote to facilitate movement?
Polymerization and breakdown of actin, and breakdown of lamellipodia.
How do chemokines assist immune cells in exiting the blood vessel?
Upregulate integrins causing cell adhesion in the vascular endothelium, followed by diapedesis into tissues.
What is the term for the process where immune cells squeeze through the endothelial cell lining of blood vessels?
Diapedesis.
List five diverse biological functions of chemokines beyond simple cell recruitment.
Lymphoid trafficking, Th1/Th2 development, Angiogenesis/angiostasis, Metastasis, Inflammation, Wound healing, Lymphoid organ development.
What term describes a chemokine receptor that binds only one specific chemokine?
Specific receptors (CXCR1 binds IL-8).
What term describes chemokine receptors that can bind multiple different chemokines?
Shared (or promiscuous) receptors (CCR1 binds MIP-1(\alpha), RANTES, MCP-2, MCP-3).
What is an example of a viral-encoded chemokine receptor and its target?
U28 (encoded by cytomegalovirus- CMV) binds CC chemokines.
What is the role of the CXCR3 receptor in organ transplantation?
CXCR3 knockout mice show reduced graft rejection; antibodies to CXCR3 ligands improve graft survival.
Which chemokine receptors are specifically associated with therapeutic trials for COPD (Chronic Obstructive Pulmonary Disease)?
CCR1, CCR5, and CXCR2.
What conditions are targeted by CCR3 small molecule antagonists and antibodies?
Asthma and allergic diseases.
Explain the basic interaction/feedback loop between cytokines and chemokines.
Cytokines induce the production of chemokines, which then selectively recruit cytokine-secreting effector cells.
Which cytokine is secreted by memory T-cells during early local inflammation to increase the homing of more memory cells, creating a self-amplifying loop?
TNF-(\alpha) (Tumour Necrosis Factor-alpha).
What are the two main host-derived stimuli for chemokine production during inflammation? (Though some bacterial/viral products also produce this).
IL-1 and TNF(\alpha).
Which specific immune cell type is attracted to the inflammatory site by Interleukin-8 (IL-8)?
Neutrophils.
Which chemokine is responsible for recruiting circulating monocytes to become tissue macrophages?
MCP (Monocyte Chemotactic Protein).
Which chemokine amplifies the recruitment of additional macrophages and effector lymphocytes during inflammation?
MIP (Monocyte Inflammatory Protein).
Which four cytokines are involved in activating macrophages to become powerful microbicidal cells?
IFN-(\gamma), GM-CSF, IL-2, and TNF.
How do IFN-(\gamma) and TNF cooperate to destroy virally infected cells? (Mechanistic explanation).
IFN-(\gamma) increases the number of TNF receptors on the surface of virally infected cells, sensitizing them to TNF-triggered apoptosis.
To which molecule type do Tc (Cytotoxic T) cells bind on antigen-presenting cells or infected targets?
MHC Class I molecules. (In contrast, Th cells bind via MHC Class II).
Which two components of lytic granules are released by Tc cells to kill an infected cell by apoptosis?
Perforin and granzymes.
What is meant by the "serial killing" capability of Tc cells?
The ability of a single Tc cell to kill one infected cell, detach, regenerate its granules, and move on to kill another cell.
Which cytokine is considered anti-inflammatory and works on macrophages and Th cells to limit inflammation?
Interleukin-10 (IL-10).
What are two examples of "decoy receptors" that can mop up free cytokines in the extracellular space?
Soluble TNF receptors (sTNF-R) and soluble IL-1 receptors (sIL-1R).
Which molecule is stimulated by IL-4 and downregulates Th1 cells during inflammation?
IL-1 receptor antagonist (IL-1Ra).
In which three clinical conditions are recombinant anti-inflammatory cytokines used as drugs?
Rheumatoid arthritis, inflammatory bowel disease (IBD), and severe sepsis.
What are two common methods for measuring the biological activity or concentration of cytokine proteins?
ELISA (using antibodies) and bioassays (using factor-dependent cell lines).
Which assay is used for the quantitation of cytokines by detecting the presence of mRNA encoding specific cytokines?
RT-PCR (Reverse Transcription Polymerase Chain Reaction).
What is the name for specialized immortalized cell lines that require specific exogenous growth factors or cytokines to proliferate and survive?
Factor-dependent cell lines.
Which two hormones are known to suppress the immune response (IR)?
Glucocorticoids and androgens.
Which four hormones act as enhancers of the immune response?
Estrogens, GH (growth hormone), thyroxine, and insulin.
Which pro-inflammatory cytokines stimulate the hypothalamic-pituitary-adrenal (HPA) axis to release glucocorticoids? (Mentioned in the context of the HPA feedback loop).
IL-1, IL-6, and TNF-(\alpha).
What is the primary role of the glucocorticoids released through the HPA axis in response to cytokines?
To provide negative feedback on immune cells and the hypothalamus, limiting and resolving inflammation.
How does estrogen affect the immune response differently in females compared to males? (Include the clinical implication).
Estrogens enhance IR (higher serum Ig, stronger B-cell response to antigens). This enhancement is linked to higher rates of autoimmune diseases in women.
What are the immunological consequences of protein deficiency?
It impairs cell-mediated immunity (CMI) by reducing Th cell numbers and function, and it decreases lysosomal enzymes in macrophages.
Which vitamin is produced by activated macrophages and works to inhibit Th1 responses while promoting Th2 responses?
Vitamin D.
What two main cytokine shifts are associated with aging? (Mention specifically which interleukins increase or decrease).
A decline in IL-2 synthesis (T-cell-mediated immune response) and an increase in pro-inflammatory cytokines (TNF, IL-1, IL-6).
Based on the HIV comparative study, which cytokine levels are significantly high versus low in infected individuals? (Mention IL-10 and IL-12).
IL-10 (high in HIV-infected individuals, anti-inflammatory/immunosuppressive) and IL-12 (low in HIV-infected individuals, pro-inflammatory/antiviral).
What are virokines and viroceptors, and what is their role in viral infection?
Viral-encoded cytokines (virokines) or receptors (viroceptors) that antagonize the effects of host antiviral cytokines.
Which class of cytokines stimulates hematopoietic stem cells to differentiate into specific blood cell types for treating anemia and leukemia?
Hematopoietic cytokines (e.g., SCF, TPO, EPO, GM-CSF, G-CSF).
Which cytokine is primarily responsible for the production of erythrocytes from erythroid progenitors? (Found in the hematopoietic diagram).
Erythropoietin (EPO).
Which cytokine primarily promotes the differentiation of myeloblasts into neutrophils?
G-CSF (Granulocyte colony-stimulating factor).
Which cytokine stimulates megakaryocytes to produce platelets?
Thrombopoietin (TPO).
Which three interleukins are involved in the development of Natural Killer (NK) cells? (Based on the hematopoiesis diagram and cytokine text).
IL-2, IL-7, and IL-15.
What are the basic steps involved in adoptive immunotherapy using cytokines? (Describe the process).
Extraction of tumor-specific T-cells from tumor tissue, selection and activation of these cells (using IL-2), and infusion back into the patient after lymphodepletive chemotherapy.
In what four specific medical contexts are cytokines used as therapeutic interventions?
Anemia, leukemia, clotting issues, and tumor therapy.
