lecture 14

Question 1

innate defenses

Answer 1

General and immediate response type, it is nonspecific and responds to a wide range of pathogens in generally the same way. Some components are: physical barriers, chemical barriers (phagocytes, NK cells, dendritic cells), cellular defenses, inflammatory responses, complement system, memory, and speed.

Question 2

adaptive

Answer 2

Is targeted and slower, but is more precise. Is specific to particular pathogens and recognizes unique antigens on pathogens. Some components are; B cells, T cells, antibodies, memory cells,

Question 3

immunity

Answer 3

immunity is the state of being insusceptible or resistant to a noxious agent or process, especially a pathogen or infectious disease. Immunity may occur naturally or be produced by prior exposure or immunization.

Question 4

immune system

Answer 4

a complex network of organs, cells, and proteins that protects the body from infections and other diseases. It recognizes and destroys foreign substances, such as bacteria, viruses, parasites, and toxins. The immune system also plays a role in fighting cancer and autoimmune disorders

Question 5

role and action of neutrophils

Answer 5

Role: Neutrophils are the first responders to infections, particularly bacterial infections. They move rapidly to the site of infection and engulf (phagocytize) pathogens, especially bacteria.
Action: They also release enzymes and antimicrobial peptides to kill pathogens. Neutrophils can trigger inflammation and are essential in the early stages of infection.

Question 6

role and action of macrophages

Answer 6

Role: Macrophages are large, phagocytic cells that ingest and digest pathogens, dead cells, and debris. They are present in tissues and act as long-term responders to infections.
Action: They also play a role in initiating adaptive immune responses by presenting antigens from the pathogens they consume to T cells (antigen presentation). Macrophages release cytokines that help regulate the inflammatory response and recruit other immune cells to the site of infection.

Question 7

role and action of dendritic cells

Answer 7

Role: Dendritic cells act as key antigen-presenting cells (APCs) in the innate immune system. They capture and process pathogens, then migrate to lymph nodes where they present the processed antigens to T cells, bridging the gap between the innate and adaptive immune systems.
Action: Dendritic cells are essential for initiating the adaptive immune response, as they activate T cells by presenting antigens via MHC molecules.

Question 8

role and action of natural killer cells

Answer 8

Role: NK cells are involved in identifying and killing cells infected by viruses or transformed by cancer. They can detect abnormal cells that do not present normal MHC class I molecules (a sign of infection or transformation).
Action: NK cells release cytotoxic granules that induce apoptosis (cell death) in infected or abnormal cells. They are important in viral infections and tumor surveillance.

Question 9

role and action of eosinophils

Answer 9

Role: Eosinophils are involved in combating parasitic infections, particularly those caused by multicellular organisms like helminths (worms).
Action: They release toxic proteins that kill parasites and are also involved in allergic reactions. Eosinophils help modulate inflammation in response to these pathogens.

Question 10

role and action of basophils

Answer 10

Role: Basophils are involved in inflammatory responses, especially during allergic reactions and parasitic infections.
Action: They release histamine and other chemicals that increase blood flow and permeability of blood vessels, leading to inflammation. Basophils contribute to the early stages of immune responses.

Question 11

Explain ways in which the innate (nonspecific) and adaptive (specific) immune responses cooperate to enhance the overall resistance to disease.

Answer 11

o The innate immune system provides a fast, general defense and “primes” the body for adaptive immune responses.
o The adaptive immune system offers a targeted, specific response with memory, enabling a faster and stronger defense during future infections.
o Key collaborations, such as antigen presentation by dendritic cells, cytokine signaling, and the complement system, allow both systems to enhance each other’s function, leading to more efficient pathogen elimination and long-term immunity.

Question 12

skin acting as a membrane barrier, describe the physical, chemical, and microbiological mechanisms of defense

Answer 12

o Skin – acts as a tough, impermeable barrier that physically prevents pathogens form entering the body. The skin secretes sebaceous glands which in turn produce sebum. The skin is home to a variety of commensal bacteria to outcompete pathogenic microbes.

Question 13

mucous membranes acting as a membrane barrier, describe the physical, chemical, and microbiological mechanisms of defense

Answer 13

The membrane produce mucus which prevents penetration from outside objects. The mucous membrane contains lysozyme which can breakdown the bacterial walls. They also have antimicrobial peptides which can act against a variety of things.

Question 14

tears and saliva acting as a membrane barrier, describe the physical, chemical, and microbiological mechanisms of defense

Answer 14

They help to flush out foreign particles and objects from around the eyes and mouth. Have lysozymes, and lactoferrin which binds to iron and deprives the bacteria of nutrients. Also, have commensal bacteria in the microbial environment to prevent pathogenic microorganisms from colonizing.

Question 15

GI tract acting as a membrane barrier, describe the physical, chemical, and microbiological mechanisms of defense

Answer 15

Has an epithelial lining acting as a physical barrier. The stomach produces gastric acid which destroys a lot of ingested pathogens. Also secretes bile. It is also home to a vast and diverse population of beneficial microbiota.

Question 16

respiratory tract acting as a membrane barrier, describe the physical, chemical, and microbiological mechanisms of defense

Answer 16

Have cilia on the nasal passages to help move mucous and trapped pathogens along. This tract secreted music which helps prevent pathogens form entering.

Question 17

urinary tract acting as a membrane barrier, describe the physical, chemical, and microbiological mechanisms of defense

Answer 17

This system has a flush mechanism to help with frequent urination and exposure to sickness

Question 18

diapedesis

Answer 18

the passage of blood cells through the intact walls of the capillaries, typically accompanying inflammation.

Question 19

chemotaxis

Answer 19

movement of a motile cell or organism, or part of one, in a direction corresponding to a gradient of increasing or decreasing concentration of a particular substance.

Question 20

opsonization

Answer 20

an immune process that helps the body identify and destroy foreign particles, like pathogens and old cells

Question 21

membrane attack complex

Answer 21

a protein complex that forms pores in cell membranes, which can destroy pathogens. It’s part of the innate immune system’s defense against infection

Question 22

what is phagocytosis

Answer 22

o The process by which certain immune cells engulf and digest pathogens, dead cells, and other debris to protect the body from infection. It is a crucial mechanism in both the innate and adaptive immune responses, particularly for clearing infections

Question 23

the steps of phagocytosis

Answer 23

 Chemotaxis – when the pathogens invade, they release molecules which signal to attract the phagocytic cells to the infection site. (neutrophils and macrophages)
 Adherence – when the phagocyte recognizes and binds to the PAMPs. (macrophage)
 Engulfment – when the phagocyte engulfs the pathogen (neutrophil and macrophage)
 Phagosome formation – when the engulfed pathogen is enclosed withing a membrane bound vesicle called the phagosome. (occurs in cells like macrophages and dendritic cells)
 Phagolysosome formation – when the phagosome fuses with the lysosome and forms a phagolysosome (macrophage, neutrophil)
 Digestion – when the pathogen phagolysosome (macrophage, neutrophil, hydrolytic enzyme, reactive oxygen species, and nitric acid
 Exocytosis – moving the material out of the cell

Question 24

Describe the functions of natural killer cells.

Answer 24

o lymphocyte (white blood cell) that play a critical role in the body’s defense against infections and tumor formation. Unlike other immune cells that require activation through antigen-specific recognition, NK cells can recognize and kill compromised cells without the need for prior sensitization. They are an essential component of the innate immune system and are particularly effective at targeting and eliminating cells infected by viruses or transformed by cancer.

Question 25

Explain how complement and interferon function as antimicrobial chemicals.

Answer 25

Complement system - The complement system consists of a group of plasma proteins that circulate in the bloodstream in an inactive form. When activated, they enhance the body’s ability to fight infections by promoting inflammation, opsonization, and direct destruction of pathogens.  Interferons primarily help the body defend against viral infections. When a cell becomes infected with a virus, it releases type I interferons (mainly IFN-α and IFN-β).  These interferons bind to nearby uninfected cells, signaling them to produce antiviral proteins that inhibit viral replication.  They also increase the expression of MHC Class I molecules, making infected cells more visible to cytotoxic T cells, which can eliminate the infected cells.  Example: IFN-β released by an infected cell causes neighboring cells to produce proteins like PKR (protein kinase R), which interfere with viral replication and prevent the spread of the virus

Question 26

Describe the mechanisms that initiate inflammation.

Answer 26

o is a crucial part of the body's immune response to infection, injury, or harmful stimuli. It is a complex biological process that helps the body defend against pathogens, repair tissue damage, and restore homeostasis. Inflammation can be acute (short-term) or chronic (long-term), but the initial response is typically part of the innate immune system. The mechanisms that initiate inflammation involve multiple signaling pathways and cellular activities.

Question 26

the cells involved in inflammatory process

Answer 26

 Macrophages: These are the primary immune cells that detect pathogens and injury. They release pro-inflammatory cytokines (like TNF-α, IL-1, IL-6) and chemokines to recruit other immune cells to the site of infection or damage.  Neutrophils: These are the first responders in acute inflammation, quickly migrating to the site of injury or infection, where they engulf pathogens and release enzymes to neutralize them.  Dendritic cells: Act as antigen-presenting cells, capturing pathogens and activating T-cells to trigger adaptive immune responses.  Mast cells: These cells release histamine and other chemicals that promote vasodilation (widening of blood vessels) and increase vascular permeability to allow immune cells to enter tissues more easily.  T-cells and B-cells: These are involved in adaptive immunity. T-cells help direct the immune response, and B-cells produce antibodies that neutralize pathogens.  Endothelial cells: These line blood vessels and play a role in regulating the passage of immune cells and proteins from the bloodstream into tissues during inflammation.

Question 27

key chemicals in the inflammatory process

Answer 27

 Cytokines: Small proteins that mediate and regulate immune and inflammatory responses. Key cytokines in inflammation include:  Tumor Necrosis Factor-alpha (TNF-α): Promotes inflammation by activating other immune cells and increasing the production of additional cytokines.  Interleukins (IL-1, IL-6, IL-8): These cytokines support immune cell activation and enhance the inflammatory process.  Chemokines: A subset of cytokines that specifically guide the migration of immune cells to the site of infection or injury (e.g., IL-8 attracts neutrophils).  Prostaglandins: Lipid compounds that mediate pain, fever, and inflammation. They are produced from arachidonic acid by cyclooxygenase (COX) enzymes.  Leukotrienes: Also derived from arachidonic acid, they help regulate blood flow and immune cell infiltration at the site of inflammation.  Histamine: Released by mast cells, it causes blood vessels to dilate and increases their permeability, allowing immune cells to enter tissues.  * Platelet-activating factor (PAF): A lipid mediator that contributes to inflammation by increasing vascular permeability and promoting platelet aggregation.

Question 28

the four cardinal signs of inflammation

Answer 28

o Redness, heat, swelling, and pain. All have a specific cause that is relates to the underlying immune processes. These four are a hallmark of the body’s protective response to injury, infection, or harmful stimuli.

Question 29

the four cardinal signs of inflammation explained

Answer 29

 Redness – is often increased blood flow to the affected area  Heat – is caused by increased blood flow and metabolic activity in the inflamed tissue  Swelling – caused by increased vascular permeability and the accumulation of fluid (edema) in the tissues  Pain – is caused by the release of chemical mediators that sensitize nerve endings and pressure from swelling.

Question 30

benefits of inflammation

Answer 30

o Inflammation is a crucial and protective response of the immune system to injury, infection, or harmful stimuli. While it can lead to discomfort and damage in the short term, inflammation has several important benefits that are essential for the body's ability to fight infections and repair damaged tissues  Pathogen elimination, increased blood flow, phagocytosis, activity

Question 31

what is fever

Answer 31

o Fever is a common systemic response to infection or inflammation, characterized by an increase in body temperature. It serves as a defense mechanism by enhancing the immune response and making the environment less favorable for pathogens.

Question 32

what are pyrogens

Answer 32

Pyrogens are substances that induce fever by causing the hypothalamus to raise the body’s temperature at a set point.

Question 33

exogenous and endogenous pyrogen

Answer 33

 Exogenous – typically microbial component or other foreign substances that infect the body.  Endogenous – are molecules that are produced by the body’s own immune system in response to infection or injury. Cytokines and interleukins

Question 34

the steps for mechanisms of fever

Answer 34

 Step 1: detection of infection or inflammation: the body will detect an infection, injury, or harmful stimuli, and immune cells such as macrophages and dendritic cells release  Step 2: activation of the hypothalamus: helps to regulate body temperature and stimulates production of prostaglandin.  Step 3: Physiological responses to raise temperature: the blood vessels will constrict to minimize heat loss, and the vessels then constrict. Once this happens the muscles will voluntarily contract and cause shivering and an increased metabolic rate.

Question 35

the purpose and effects of a fever

Answer 35

 Enhanced Immune Function: Higher body temperature can increase the activity of immune cells such as neutrophils and macrophages, improving their ability to fight infections. It also accelerates the production of antibodies and other immune responses.  Inhibiting Pathogens: Many pathogens, especially bacteria and viruses, have an optimal growth temperature. Raising the body’s temperature can hinder their ability to replicate, slowing down the infection.  Acute Phase Response: Fever is often part of the acute phase response, a systemic reaction that includes the release of proteins like C-reactive protein (CRP) from the liver, which helps modulate immune responses.