Inflammation and Immune Response

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Questions and Answers

Which mechanism directly results in the migration of leukocytes to the site of inflammation?

Adhesion to endothelial cells

Transmigration through blood vessels (correct)

Vasodilation of blood vessels

Pro-inflammatory cytokine release

What role do macrophages play in the inflammatory response following tissue injury?

Secretion of complement proteins

Release of IgE antibodies

Phagocytosis of pathogens only

Activation of mast cells (correct)

What is the primary outcome of vascular permeability during inflammation?

Leukocyte accumulation in the bloodstream

Hyperemia leading to overactive immune response

Edema due to fluid leakage (correct)

Increased blood circulation

What effect does mast cell activation have during an inflammatory response?

Release of pro-inflammatory mediators Signup and view all the answers

What is the result of delayed vascular stasis during inflammation?

Controlled blood flow allowing immune cell access Signup and view all the answers

Which cells are the first to migrate to the area of inflammation in response to chemotactic signals?

Leukocytes Signup and view all the answers

The accumulation of immune cells in the tissues during inflammation is predominantly facilitated by which process?

Margination Signup and view all the answers

Which of the following best describes how pathogens are typically destroyed during inflammation?

By phagocytosis and extracellular killing Signup and view all the answers

Which statement accurately describes the role of venous valves in the circulatory system?

They prevent blood from moving retrograde and ensure it flows back to the heart. Signup and view all the answers

How does body position impact venous return?

Laying down reduces venous capacity, making it easier for blood to return to the heart. Signup and view all the answers

Which factor primarily decreases venous capacity, thus promoting venous return during exercise?

Sympathetic nervous system activation leading to vasoconstriction. Signup and view all the answers

What effect does skeletal muscle activity have on venous return?

It compresses veins, promoting the movement of blood towards the heart. Signup and view all the answers

Which of the following best explains the concept of compliance in veins related to their capacity?

Higher compliance allows for greater volume accommodation within the veins. Signup and view all the answers

What is the main factor that influences mean arterial pressure (MAP) during vasodilation?

Decrease in total peripheral resistance Signup and view all the answers

How is cardiac output distributed differently during moderate exercise compared to rest?

More blood directed to skeletal muscles during exercise Signup and view all the answers

What role does the sympathetic nervous system play during exercise regarding blood flow?

Increases heart rate and stroke volume Signup and view all the answers

Which mechanism is primarily responsible for local vasodilation in active muscles during exercise?

Metabolic byproducts stimulating endothelium Signup and view all the answers

Which hormone released during exercise primarily supports water retention to maintain blood pressure?

ADH (Vasopressin) Signup and view all the answers

Which receptor binding results in vasoconstriction of all tissues except the skeletal muscles and heart during exercise?

Alpha receptors Signup and view all the answers

What primarily causes the increase in cardiac output during exercise?

Increase in stroke volume and heart rate Signup and view all the answers

What is the effect of skeletal muscle contractions on venous return during exercise?

Increase venous return by acting as a muscle pump Signup and view all the answers

What overall effect occurs in blood flow distribution to vital organs during exercise?

Sustained blood flow to the brain with changes in other organs Signup and view all the answers

Which factor primarily helps adjust blood flow to meet the oxygen and nutrient demands of active muscles?

Redistribution of cardiac output primarily via neural mechanisms Signup and view all the answers

What happens if both the SA and AV nodes fail in the heart?

The Bundle of His or Purkinje fibers take over as a pacemaker. Signup and view all the answers

What is primarily measured by the PR interval in an EKG?

AV nodal delay. Signup and view all the answers

What would be the heart rate if there is a complete loss of parasympathetic and sympathetic innervation?

70-80 bpm. Signup and view all the answers

What electrical event follows the firing of the AV node in the cardiac cycle?

Ventricular contraction. Signup and view all the answers

Which EKG waveform represents ventricular depolarization?

QRS Complex. Signup and view all the answers

Which action occurs during passive filling of the ventricles?

Atrial pressure exceeds ventricular pressure. Signup and view all the answers

What effect does increased heart rate have on the R-R interval?

The R-R interval decreases. Signup and view all the answers

When occurs during atrial contraction in relation to ventricular pressure?

Atrial pressure exceeds ventricular pressure. Signup and view all the answers

What does the ST segment in the EKG primarily indicate?

Ejection of blood from the ventricles. Signup and view all the answers

Why does the left side of the heart have higher pressure compared to the right side?

It pumps blood into the aorta. Signup and view all the answers

Which of the following best describes the relationship between flow rate, pressure gradient, and resistance according to the formula F = ΔP/R?

Flow rate is directly proportional to the pressure gradient and inversely proportional to resistance. Signup and view all the answers

What is the primary contributor to changes in vascular resistance?

Diameter and radius of vessels changing. Signup and view all the answers

How do arteries adapt to maintain effective blood flow and pressure during systole and diastole?

By stretching during systole and rebounding during diastole. Signup and view all the answers

Which layer of the artery wall provides the elastic properties necessary for pressure storage?

Connective tissue layer with collagen and elastic fibers. Signup and view all the answers

What effect does vasodilation have on flow rate given sufficient pressure?

It decreases resistance, resulting in enhanced flow rate. Signup and view all the answers

What is mean arterial pressure (MAP) and why is it significant?

The average pressure in the arteries over a cardiac cycle, important for assessing organ perfusion. Signup and view all the answers

Which statement accurately reflects the impact of arterial wall structure on its function?

Thick, elastic walls are crucial for stable blood pressure maintenance and flow control. Signup and view all the answers

What happens to blood flow if perfusion pressure decreases while resistance increases?

Blood flow decreases due to decreased perfusion pressure and increased resistance. Signup and view all the answers

How does arterial compliance affect blood pressure during the cardiac cycle?

Low compliance prevents arteries from adapting quickly to arterial pressure changes. Signup and view all the answers

Why is blood viscosity considered a stable contributor to vascular resistance?

It remains relatively constant, influenced mainly by hematocrit. Signup and view all the answers

Which characteristic of the capillary structure primarily facilitates the exchange of gases and nutrients?

Single layer of endothelial cells forming thin walls Signup and view all the answers

What role does the precapillary sphincter serve in the regulation of blood flow?

Regulates blood flow based on local metabolic activity Signup and view all the answers

How does the small diameter of capillaries contribute to their function?

Decreases blood velocity, maximizing exchange opportunity Signup and view all the answers

Which statement accurately describes the role of gaps and pores in capillary walls?

Facilitate the escape of everything but blood cells and plasma Signup and view all the answers

What is the significance of an extensive network of capillaries in the circulatory system?

Minimizes the distance for diffusion and increases surface area Signup and view all the answers

What is the primary function of phagocytic cells within the innate immune system?

To engulf and destroy pathogens. Signup and view all the answers

Which statement best explains the difference between innate and adaptive immunity?

Innate immunity is the first line of defense and non-specific, while adaptive immunity is specific and slower to respond. Signup and view all the answers

What role do antigen-presenting cells (APCs) play in the adaptive immune response?

They present antigens to T-cells to trigger an immune response. Signup and view all the answers

What is the significance of the complement system in the innate immune response?

It enhances the ability to clear microbes and promote inflammation. Signup and view all the answers

What is the primary function of Interferon-α/β during viral infections?

Inhibit viral replication and degrade viral RNA Signup and view all the answers

Which of the following best describes the inflammatory response?

A rapid response that leads to collateral damage but is essential for healing. Signup and view all the answers

How do B and T lymphocytes differ in their response to pathogens?

B lymphocytes target extracellular pathogens, whereas T lymphocytes target intracellular pathogens. Signup and view all the answers

Which type of cells predominantly produces Interferon-γ?

Natural killer (NK) cells Signup and view all the answers

What initiates the rapid response of the adaptive immune system upon re-exposure to the same pathogen?

Memory T and B cells rapidly proliferate. Signup and view all the answers

What are the Major Histocompatibility Complex (MHC) class I molecules primarily involved in?

Presentation of antigens to CD8+ T cells Signup and view all the answers

What cellular mechanism is primarily responsible for tissue repair following inflammation?

Reproduction of healthy tissue cells. Signup and view all the answers

What effect does IL-6 have in the immune system?

Promotes synthesis of acute phase proteins Signup and view all the answers

Which of the following cytokines is primarily responsible for stimulating fat and muscle catabolism?

TNF-α Signup and view all the answers

Which cytokine has the function of both inducing fever and stimulating acute phase protein production?

IL-1 Signup and view all the answers

What is the main function of Interferon-γ besides activating NK cells?

Enhance antigen presentation Signup and view all the answers

Which cells predominantly respond to IL-1 during an inflammatory response?

Macrophages and NK cells Signup and view all the answers

What is a consequence of interferons being released during viral infections?

Activation of immune cells Signup and view all the answers

What is the primary target tissue for TNF-α to induce fever?

Hypothalamus Signup and view all the answers

What is the primary function of prostaglandins in the COX pathway?

Induce pain, fever, and cause edema Signup and view all the answers

Which cytokine is primarily involved in stimulating liver production of acute-phase proteins?

IL-6 Signup and view all the answers

How do corticosteroids function in the inflammatory response?

They inhibit the formation of prostaglandins by blocking phospholipase C Signup and view all the answers

Which of the following statements correctly describes leukotrienes' role in inflammation?

They promote bronchoconstriction and increase vascular permeability Signup and view all the answers

What is the primary role of C-reactive protein (CRP) in the acute phase response?

Facilitates pathogen recognition and clearance Signup and view all the answers

What is a key difference between the COX and LOX pathways in terms of their products?

COX pathway results in vasodilation, whereas LOX pathway causes bronchoconstriction Signup and view all the answers

Which acute-phase protein is responsible for activating the complement system?

Mannose-binding lectin (MBL) Signup and view all the answers

Which of the following is NOT a trigger for the acute phase response?

Hypoxia Signup and view all the answers

What effect do pro-inflammatory cytokines have on the liver during the acute phase response?

Stimulate production of acute-phase proteins Signup and view all the answers

Which function of the pericardium primarily facilitates smooth heart movement during contractions?

Lubrication Signup and view all the answers

What structural feature of cardiac muscle allows for rapid electrical communication between cells?

Intercalated discs Signup and view all the answers

What is a primary characteristic of the fibrous pericardium?

It is a dense connective tissue layer anchoring the heart. Signup and view all the answers

Which components of the intercalated discs provide both mechanical support and electrical coupling in cardiac muscle cells?

Gap junctions and desmosomes Signup and view all the answers

Which part of the serous pericardium directly covers the myocardium?

Epicardium Signup and view all the answers

What is the consequence of a selective blockade of gap junctions in cardiac muscle?

Decreased frequency of muscle contraction Signup and view all the answers

Which layer of the pericardium is responsible for secreting pericardial fluid?

Serous layer Signup and view all the answers

Which characteristic is NOT typical of cardiac muscle structure?

Multinucleation Signup and view all the answers

What protective function does the pericardium provide?

It acts as a barrier against infections from surrounding organs. Signup and view all the answers

Which aspect of cardiac muscle's structure is critical for electrical coupling during contraction?

Gap junctions Signup and view all the answers

Study Notes

Inflammation Triggers

Injured tissue releases cytokines, which activate macrophages.
Injured tissue activates mast cells, which release pro-inflammatory mediators.
Macrophages detect and ingest pathogens, and release pro-inflammatory mediators.
Activated macrophages stimulate mast cells, which release pro-inflammatory mediators.

Mast Cell Activation

Mast cells can be triggered by injury, interleukin I, complement proteins, and IgE, which are responsible for hypersensitivity reactions.

Vascular Migration

Occurs in the microcirculation system.
Vasodilation leads to redness and heat at the site of inflammation.
Increased permeability causes immune cells to leak into surrounding tissues, leading to albumin leak and edema.
Delayed vascular stasis helps immune cells reach the affected area while controlling blood flow.
Exudate of fluid, including fibrinogen and other plasma proteins, move into tissues to isolate the pathogen and dilute toxins, causing pain and swelling.

Cell Migration

Chemotaxis of leukocytes to the affected area.
First responders are leukocytes, followed by monocytes that differentiate into macrophages.
Margination occurs as vasodilation slows down blood flow, leading to leukocytes accumulating along blood vessel walls.
Adhesion occurs when leukocytes adhere to endothelial cells in the blood vessel lining, enabling them to move into the tissue to track down pathogens.
Transmigration involves leukocytes squeezing through the blood vessel lining and migrating to the affected tissue.

Attack of Pathogens

Pathogens are phagocytized and destroyed via extracellular killing using enzymes and ROS.
Phagocytic cells carry antigen through lymph fluid to the nearest lymph node.

Cardiac Electrical Events

SA node is the primary pacemaker of the heart and sets the natural heart rate.
AV node acts as a secondary pacemaker if the SA node fails.
Bundle of His and Purkinje fibers act as the heart's final backup pacemakers if both the SA and AV nodes fail, but at a much slower rate.

AV Nodal Delay

AV nodal delay allows for maximal ventricular filling of blood.
This delay occurs after the AV node fires an action potential, which then travels to the bundle of His and causes ventricular contraction.

Heart Rate Without Autonomic Innervation

The natural firing rate of the SA node is 70-80 beats per minute.
This is the heart rate if all parasympathetic and sympathetic innervation to the heart is cut off.

12-Lead EKG Waveforms

P Wave: Atrial Depolarization
PR Interval: Measures AV nodal delay
QRS Complex: Ventricular Depolarization
ST Segment: Ejection of blood from ventricles
T Wave: Ventricular Repolarization
TP Interval: Diastole

EKG and Heart Rate

The distance between the R-R intervals on an EKG decreases as heart rate increases.
Clinically used to measure the distance between cardiac cycles.

Cardiac Cycle

The heart cycle involves both electrical and mechanical events.
The graph only measures the left side of the heart, but the right side undergoes the same events.
The left side has higher pressure because it pumps blood into the aorta.

Cardiac Cycle Stages

Ventricular and Atrial Diastole (Passive Filling):
- Blood flows from the superior/inferior vena cava into the right atrium and then the right ventricle.
- Blood flows from the pulmonary vein into the left atrium and then the left ventricle.
- AV valves are open.
- Left atrial pressure is slightly greater than ventricular pressure, allowing the AV valves to stay open.
Atrial Contraction:
- Atrial pressure remains greater than ventricular pressure, keeping the AV valve open, and blood flows into the ventricle.
- Ventricular volume increases.
- EKG: P wave.
Isovolumetric Contraction:
- Ventricular pressure increases, causing the AV valve to close.
- No change in volume.
- First Heart Sound "LUB"
- EKG: QRS complex.
Ventricular Ejection:
- Ventricular pressure exceeds aortic pressure, causing the aortic valve to open.
- Blood is ejected from the ventricle into the aorta.
- EKG: ST Segment
Isovolumetric Relaxation:
- Ventricular pressure decreases, causing the aortic valve to close
- No change in volume.
- Second Heart Sound - "DUB"
- EKG: T wave.
Passive Ventricular Filling
- AV valve opens, and blood flows passively from atrium to ventricle

Blood Flow, Pressure, and Resistance

Blood flow is determined by pressure gradient and resistance.
Pressure Gradient:
- The difference in pressure between two points.
- Pressure gradients drive blood flow from high pressure to low pressure.
Resistance:
- Opposes blood flow.
Factors influencing resistance:
- Blood viscosity: Increased viscosity increases resistance.
- Vessel Diameter: Smaller diameter increases resistance.

Blood Flow Regulation

Blood flow can be regulated by manipulating pressure, viscosity, and diameter to achieve enhanced or decreased flow.
Enhanced Flow:
- Increased pressure and vasodilation lead to decreased resistance and enhanced blood flow.
Decreased Flow:
- Decreased pressure and vasoconstriction lead to increased resistance and decreased blood flow.

Arteries: Structure and Function

Arteries are thick, elastic walls with a muscular layer that:
- Stores pressure due to elasticity.
- Controls blood flow.
- Ensures efficient distribution of oxygenated blood to tissues.
Layers of arteries from inner to outer:
- Endothelium.
- Connective tissue layer with collagen and elastic fibers, responsible for elastic properties.
- Smooth muscle with sympathetic nerve innervation.
- External connective tissue cover.
Major functions:
- Maintain flow rate from the heart to organs.
- Maintain stable blood pressure.

Systolic vs. Diastolic Blood Pressure and MAP

Systolic Blood Pressure: Highest pressure during ventricular contraction (systole).
Diastolic Blood Pressure: Lowest pressure during ventricular relaxation (diastole).
Mean Arterial Pressure (MAP): The average pressure in the arteries over a cardiac cycle.
Importance of MAP: MAP is crucial for maintaining adequate blood flow to organs.

MAP Regulation

MAP can be regulated by controlling total peripheral resistance (TPR) through vasoconstriction and vasodilation.
Vasoconstriction increases TPR, increasing MAP.
Vasodilation decreases TPR, decreasing MAP.
The body adjusts blood flow to meet local tissue demands while maintaining systemic blood pressure.

Cardiac Output and MAP

MAP is determined by two main factors: Cardiac output (CO) and total peripheral resistance (TPR).
- Cardiac Output (CO): The volume of blood pumped by the heart per minute. CO = Heart Rate (HR) × Stroke Volume (SV).
- Total Peripheral Resistance (TPR): Resistance to blood flow in the vasculature.
MAP = CO x TPR.
MAP and TPR are interrelated and influenced by blood flow.

Cardiac Output Redistribution During Exercise

Resting: Most of the CO is distributed to vital organs.
Exercise: Increased CO (nearly 2.5 times the baseline) is primarily directed to skeletal muscles and some to the skin for heat dissipation.
Mechanisms for redistribution:
- Sympathetic Stimulation:
  - Release of epinephrine/norepinephrine from the adrenal medulla causes:
    - Vasodilation in skeletal muscles and the heart (beta-2 receptors).
    - Vasoconstriction in other tissues (alpha receptors).
    - Increased heart rate (HR) and stroke volume (SV), leading to increased CO.
    - Increased glycogen breakdown, providing glucose for energy.
- Hormonal Release:
  - Antidiuretic hormone (ADH) (released from the posterior pituitary):
    - Increases sodium retention in the kidneys, leading to increased water retention and blood pressure maintenance.
  - Aldosterone (adrenal cortex):
    - Increases water retention in the kidneys, preventing dehydration and maintaining blood pressure.
- Local Metabolic Changes: Active muscles produce metabolic byproducts (CO2, lactic acid, and adenosine) that trigger local vasodilation, increasing blood flow to meet the demand.
- Muscle Pump Mechanism: Muscle contractions act as a pump, increasing venous return and CO.
- Redistribution by Arterioles: Arterioles redistribute cardiac output according to body demands.
Overall: Total CO increases, blood flow increases to skeletal muscles, heart, and skin, while brain blood flow remains the same, and blood flow to other organs decreases.

Capillaries: Structure and Function

Functions:
- Transport deoxy blood from tissues to the heart (except pulmonary vein).
- Serve as a blood reservoir, holding 60-70% of blood flow at rest.
How Structure Supports Function:
- High compliance and capacitance enable adaptation to volume changes.
- Thin walls and large lumen accommodate blood volume.
- Valves prevent backflow, ensuring unidirectional flow back to the heart.
- Reduced smooth muscle contributes to flexibility and adaptation to volume and pressure changes, enabling blood storage.

Venous Return

Venous capacity refers to the ability of veins to hold and store blood.
Factors affecting venous capacity:
- Vein Compliance: Increased compliance increases capacity.
- Body Position: Standing or sitting increases venous pooling, decreasing venous capacity and return. Lying down decreases venous capacity, facilitating venous return.
- SNS Activation: SNS activation during exercise or stress decreases venous capacity, increasing venous return to the heart and active muscles.
- Blood Volume: Increased blood volume increases pressure and compliance, therefore increasing capacity.
Venous Return: The flow of blood back into the right atrium of the heart.
Determinants of Venous Return:
- SNS Vasoconstriction:
  - Decreases venous capacity, increasing venous return to the heart and active muscles.
- Skeletal Muscle Activity:
  - Muscle contractions compress veins, pushing blood towards the heart.
- Venous Valves:
  - Ensure blood flow towards the heart and prevent backflow.
- Respiratory Activity:
  - Inhalation decreases thoracic pressure and increases abdominal pressure, drawing blood towards the thoracic cavity.
- Cardiac Suction:
  - Ventricular contraction decreases atrial volume, lowering atrial pressure and increasing venous return.

Innate Immune System

First line of defense, non-specific
Includes physical and chemical barriers
Phagocytic cells include macrophages and dendritic cells
Inflammatory response
Plasma protein systems: complement system, clotting system, and kinin system

Adaptive Immune System

Specific, slower to respond
Provides long-lasting immunity
B lymphocytes (antibody-mediated immunity)
T lymphocytes (cell-mediated immunity)
Memory cells learn from past experiences
More frequent encounters with pathogens lead to faster and more effective responses

Antigen Presenting Cells (APCs)

Macrophages: present antigens to T cells, triggering the immune system
Dendritic cells: most efficient antigen-presenting cells
Present antigens to T cells in lymphoid tissues
Initiate the production of pathogen-specific T cells and B cells

Inflammation and Collateral Damage

Arachidonic acid: essential in the inflammatory response
Metabolized via two pathways: cyclooxygenase (COX) and lipoxygenase (LOX) pathways
COX pathway: produces prostaglandins, which cause vasodilation, increased vascular permeability, edema, pain, and fever
LOX pathway: produces leukotrienes, which attract and activate neutrophils, cause bronchoconstriction, and increase vascular permeability.

Acute Phase Response

Systemic reaction triggered by inflammation
Mobilizes the body's defenses to limit damage and promote healing
Triggers include pro-inflammatory cytokines like IL-1, IL-6, and TNF-α, released by macrophages and neutrophils
Elevated cytokine release leads to increased liver production of acute-phase proteins
CRP (C-reactive protein): enhances opsonization and pathogen clearance
MBL (mannose-binding lectin): activates complement and aids pathogen recognition

Cytokines Involved in Acute Phase Response

IL-1: targets hypothalamus (induces fever), liver (acute-phase protein production), and bone marrow (leukocyte production)
IL-6: targets liver (acute-phase protein production), bone marrow (leukocyte production), and fat/muscle (mobilizes energy)
TNF-α: targets hypothalamus (induces fever), liver (acute-phase protein production), and adipose tissue (metabolic changes)

Interferons

Signaling proteins inhibiting viral replication and activating immune cells
Released during viral infections
Produced by virus-infected cells: macrophages, dendritic cells, and fibroblasts
Interferon-α/β: inhibit viral replication, degrade viral RNA, and increase MHC class I expression for enhanced antigen presentation
Interferon-γ: activates NK cells and strengthens the immune response

Immune Response to Viral Infections

Innate immune system components, such as natural killer (NK) cells and macrophages, fight the infection initially, prior to the T cell response

Major Histocompatibility Complex (MHC) Molecules

Involved in antigen presentation and immune recognition
Class I MHC: found on all nucleated cells, presents antigens to cytotoxic T cells
Class II MHC: found on antigen-presenting cells (APCs), presents antigens to helper T cells

Pericardium

Sac surrounding the heart
Composed of three layers: fibrous pericardium, serous pericardium, and pericardial fluid
Functions include protection, anchorage, and lubrication

Cardiac Muscle

Striated muscle with organized intracellular proteins for contraction
Branching pattern with intercalated discs
Intercalated discs contain desmosomes (physical anchors) and gap junctions (electrically couple cells)

Intercalated Discs

Gap junctions allow rapid spread of action potentials (APs) throughout the muscle
Ensure synchronous contraction
Selective blockade of gap junctions could disrupt coordinated cardiac muscle contraction

Capillary Structure and Function

Thin walls: single layer of endothelial cells for gas, nutrient, and waste exchange
No smooth muscle or connective tissue: flexibility and permeability
Small diameter: slows blood velocity and maximizes exchange
Extensive network: minimizes diffusion distance and maximizes surface area
Cross-sectional area increases at capillary beds, slowing blood flow
Gaps and pores: allow passage of everything except cells and plasma

Metarteriole

Connect arterioles to capillary beds
Pathway that can bypass capillaries, directly connecting to venules
Smooth muscle allows control over blood flow into capillaries

Precapillary Sphincter

Regulates blood flow into capillaries based on tissue demand
Constricts during rest, restricting blood flow
Relaxes during exercise, allowing unrestricted blood flow into capillaries

Capillary Bulk Flow

Passive process driven by pressure gradients
Fluid movement from capillaries into interstitial fluid
Influenced by hydrostatic pressure (blood pressure) and osmotic pressure (protein concentration)

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Description

This quiz explores the mechanisms of inflammation, including cytokine release, mast cell activation, and vascular responses. Understand how these processes contribute to tissue healing and immune defense against pathogens. Test your knowledge on the cellular interactions that drive inflammation.