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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{Rim}} (Reviewed by {{YD}})
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Immunology
|MainCategory=Immunology
Line 21: Line 21:
|MainCategory=Immunology
|MainCategory=Immunology
|SubCategory=General Principles
|SubCategory=General Principles
|Prompt=A 6-year-old female was brought to her pediatrician for fever and runny nose. The fever started two days ago and has not been responsive to anytipyritics. Which of the following inflammatory mediators is involved in the patient’s fever?
|Prompt=A 6-year-old girl is brought to her pediatrician's office for fever and runny nose. The fever started 2 days ago and has not been responsive to anytipyretic agents. Which of the following inflammatory mediators is involved in the patient’s fever?
|Explanation=L-1 is intensely produced by tissue [[macrophages]], [[monocytes]], [[fibroblast]]s, and dendritic cells, but is also expressed by B lymphocytes, NK cells and epithelial cells. They form an important part of the inflammatory response of the body against infection. These [[cytokine]]s increase the expression of adhesion factors on endothelial cells to enable transmigration (also called [[diapedesis]]) of immunocompetent cells, such as phagocytes, lymphocytes and others, to sites of infection. It also affects the activity of [[hypothalamus]], the thermoregulatory center, which lead to a raise of a body temperature, so called [[fever]].  That is why [[IL-1]] is called endogenous [[pyrogen]]. Besides of fever, IL-1 also causes hyperalgesia (increased pain sensitivity), [[vasodilation]] and [[hypotension]].
|Explanation=The average oral temperature of the human body is 37 °C (98.6 °F) and is strictly regulated under physiologic conditions by the hypothalamus. Fever is considered the hallmark of immune system activation. It is defined as an elevation of core body temperature that occurs by a cytokine-mediated inflammatory response. Fever is mediated by 2 triggers: endogenous pyrogens/cytokines and exogenous pyrogens. Both endogenous and exogenous pyrogens can act together to induce fever. Exogenous compounds, such as lipopolysaccarides (LPS) on gram-negative bacteria, induce the production of endogenous pro-inflammatory cytokines, such as IL-1, IL-6, INF-alpha, and TNF. Of all, IL-6 is the principal endogenous pyrogen and the strongest correlate to fever. These cytokines cross the blood brain barrier and access the hypothalamic circulation, release local prostaglandins, and reset the hypothalamic thermal setpoint to elevate the core body temperature. Fever is characterized by 3 clinical phases:<br>
|AnswerA=Interleukin 1
#Chill/cold phase: Characterized by activities that increase the core body temperature to meet the new setpoint via 2 mechanisms: cutaneous vasoconstriction to prevent peripheral heat loss and shivering muscle activity to generate heat.
|AnswerAExp=Interleukin 1 affects the activity of [[hypothalamus]], the thermoregulatory center, which leads to a raise of a body temperature, so called [[fever]].  That is why [[IL-1]] is called endogenous [[pyrogen]].
#Fever phase: Characterized by warmth, flushing. In this phase, the generation and loss of heat are balanced and equal.
|AnswerB=Interleukin 2
#Flush phase: Characterized by diaphoresis and cutaneous vasodilation. Setpoint returns to normal, and body loses excessive heat.  
|AnswerBExp=Interleukin 2 is necessary for the growth, proliferation, and differentiation of [[T cells]] to become 'effector' T cells. It is secreted by the T helper cells.  Interleukin 2 is not pyrogenic.
|AnswerC=Interleukin 3
|AnswerCExp=Interleukin 3 is secreted by [[basophil]]s and activated [[T cells]] to support growth and differentiation of T cells from the [[bone marrow]] in an immune response.  Interleukin 3 is not pyrogenic.
|AnswerD=Interleukin 4
|AnswerDExp=Interleukin 4 induces [[B-cell]] class switching to [[IgE]], and up-regulates MHC class II production. IL-4 decreases the production of Th1 cells, macrophages, IFN-gamma, and dendritic cell IL-12.  Interleukin 4 is not pyrogenic.
|AnswerE=Interleukin 5
|AnswerEExp=Interleukin 5 is a major regulator of [[eosinophil]] accumulation in tissues, and can modulate eosinophil behavior at every stage from maturation to survival.  Interleukin 5 is not pyrogenic.
|EducationalObjectives=Shown below is an image summarizing the roles of interleukins and the cells that secrete them.


While some cytokines act as endogenous pyrogens, IL-10, arginine vasopressin, melanocyte-stimulating hormone, and glucocorticoides are considered endogenous antipyretics. Pharmacologic agents may also be antipyretics, such as acetaminophen, aspirin, and NSAIDs. Fever should be differentiated from hyperthermia, whereby the temperature setpoint in hyperthermia is not increased but the ratio of heat generation and heat dissipation is imbalanced. Exertional and non-exertional heat strokes are 2 examples of hyperthermia. Antipyretics are not effective in hyperthermia. Instead, rapid cooling using ice water (for exertional heat stroke) and passive cooling using fans (non-exertional heat stroke) are more useful in hyperthermia.
Shown below is a table that summarizes the roles of interleukins and the cells that secrete them.
[[File:Interleukin.png]]
[[File:Interleukin.png]]
|References=First Aid 2014 page 205
|AnswerA=IL-1
|AnswerAExp=IL-1 affects the activity of the [[hypothalamic]] thermoregulatory center, which leads to an increase in the core body temperature that results in fever. IL-1 is an endogenous pyrogen.
|AnswerB=IL-2
|AnswerBExp=IL-2 is necessary for the growth, proliferation, and differentiation of [[T cells]] to become effector T cells.  It is secreted by T helper cells.
|AnswerC=IL-3
|AnswerCExp=IL-3 is secreted by [[basophil]]s and activated [[T cells]] to support growth and differentiation of T cells from the [[bone marrow]] during an immune response.
|AnswerD=IL-4
|AnswerDExp=IL-4 induces [[B-cell]] class switching to [[IgE]] and up-regulates MHC class II production. IL-4 decreases the production of Th1 cells, macrophages, IFN-gamma, and dendritic cells.
|AnswerE=IL-5
|AnswerEExp=IL-5 is a major regulator of [[eosinophil]] accumulation in tissues.
|References=Dalal S, Zhukovsky DS. Pathophysiology and management of fever. J Support Oncol. 2006;4(1):9-16.<br>
First Aid 2014 page 205
|RightAnswer=A
|RightAnswer=A
|WBRKeyword=Interleukin, Fever
|WBRKeyword=Interleukin, Fever, IL-1, Endogenous, Exogenous, Pyrogen, Hypothalamus, Core body temperature
|Approved=Yes
|Approved=Yes
}}
}}

Revision as of 21:14, 31 October 2014
Author [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Immunology
Sub Category SubCategory::General Principles
Prompt [[Prompt::A 6-year-old girl is brought to her pediatrician's office for fever and runny nose. The fever started 2 days ago and has not been responsive to anytipyretic agents. Which of the following inflammatory mediators is involved in the patient’s fever?]]
Answer A AnswerA::IL-1
Answer A Explanation [[AnswerAExp::IL-1 affects the activity of the hypothalamic thermoregulatory center, which leads to an increase in the core body temperature that results in fever. IL-1 is an endogenous pyrogen.]]
Answer B AnswerB::IL-2
Answer B Explanation [[AnswerBExp::IL-2 is necessary for the growth, proliferation, and differentiation of T cells to become effector T cells. It is secreted by T helper cells.]]
Answer C AnswerC::IL-3
Answer C Explanation [[AnswerCExp::IL-3 is secreted by basophils and activated T cells to support growth and differentiation of T cells from the bone marrow during an immune response.]]
Answer D AnswerD::IL-4
Answer D Explanation [[AnswerDExp::IL-4 induces B-cell class switching to IgE and up-regulates MHC class II production. IL-4 decreases the production of Th1 cells, macrophages, IFN-gamma, and dendritic cells.]]
Answer E AnswerE::IL-5
Answer E Explanation [[AnswerEExp::IL-5 is a major regulator of eosinophil accumulation in tissues.]]
Right Answer RightAnswer::A
Explanation [[Explanation::The average oral temperature of the human body is 37 °C (98.6 °F) and is strictly regulated under physiologic conditions by the hypothalamus. Fever is considered the hallmark of immune system activation. It is defined as an elevation of core body temperature that occurs by a cytokine-mediated inflammatory response. Fever is mediated by 2 triggers: endogenous pyrogens/cytokines and exogenous pyrogens. Both endogenous and exogenous pyrogens can act together to induce fever. Exogenous compounds, such as lipopolysaccarides (LPS) on gram-negative bacteria, induce the production of endogenous pro-inflammatory cytokines, such as IL-1, IL-6, INF-alpha, and TNF. Of all, IL-6 is the principal endogenous pyrogen and the strongest correlate to fever. These cytokines cross the blood brain barrier and access the hypothalamic circulation, release local prostaglandins, and reset the hypothalamic thermal setpoint to elevate the core body temperature. Fever is characterized by 3 clinical phases:
  1. Chill/cold phase: Characterized by activities that increase the core body temperature to meet the new setpoint via 2 mechanisms: cutaneous vasoconstriction to prevent peripheral heat loss and shivering muscle activity to generate heat.
  2. Fever phase: Characterized by warmth, flushing. In this phase, the generation and loss of heat are balanced and equal.
  3. Flush phase: Characterized by diaphoresis and cutaneous vasodilation. Setpoint returns to normal, and body loses excessive heat.

While some cytokines act as endogenous pyrogens, IL-10, arginine vasopressin, melanocyte-stimulating hormone, and glucocorticoides are considered endogenous antipyretics. Pharmacologic agents may also be antipyretics, such as acetaminophen, aspirin, and NSAIDs. Fever should be differentiated from hyperthermia, whereby the temperature setpoint in hyperthermia is not increased but the ratio of heat generation and heat dissipation is imbalanced. Exertional and non-exertional heat strokes are 2 examples of hyperthermia. Antipyretics are not effective in hyperthermia. Instead, rapid cooling using ice water (for exertional heat stroke) and passive cooling using fans (non-exertional heat stroke) are more useful in hyperthermia.

Shown below is a table that summarizes the roles of interleukins and the cells that secrete them.
Educational Objective:
References: Dalal S, Zhukovsky DS. Pathophysiology and management of fever. J Support Oncol. 2006;4(1):9-16.
First Aid 2014 page 205]]

Approved Approved::Yes
Keyword WBRKeyword::Interleukin, WBRKeyword::Fever, WBRKeyword::IL-1, WBRKeyword::Endogenous, WBRKeyword::Exogenous, WBRKeyword::Pyrogen, WBRKeyword::Hypothalamus, WBRKeyword::Core body temperature
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