Module 4 - Chapter 6 - Innate Immunity - First Line

Question 1

What is innate immunity, and what does it include?

Answer 1

Innate immunity, also known as natural or native immunity, consists of natural barriers (physical and biochemical) and inflammation. These are the body’s first line of defense against injury and infection.

Question 2

How do physical and biochemical barriers contribute to innate immunity?

Answer 2

Physical and biochemical barriers are in place at birth to prevent damage by environmental substances and protect against infection by pathogens. They form the initial defense at the body’s surfaces.

Question 3

What is the role of surface barriers in innate immunity, and what are the “normal flora”?

Answer 3

Surface barriers protect against injurious agents and can harbor a group of microorganisms known as “normal flora,” which help protect against pathogens.

Question 4

When do the second line of defense mechanisms, such as the inflammatory response, become active in the body?

Answer 4

The second line of defense, including the inflammatory response, is activated when injurious agents breach surface barriers. It aims to protect against further injury, prevent infection, and promote healing.

Question 5

Describe the nature of the inflammatory response in innate immunity.

Answer 5

The inflammatory response is a rapid activation of nonspecific biochemical and cellular mechanisms that protect the body from various causes of tissue damage, regardless of the tissue type.

Question 6

What is the third line of defense in the immune system, and what distinguishes it from innate immunity?

Answer 6

The third line of defense is adaptive (acquired) immunity, also known as specific immunity. It is slower and more specific in targeting particular invading microorganisms, often involving “memory” for quicker responses upon future exposure.

Question 7

What is the level of defense associated with barriers in the immune system?

Answer 7

Barriers represent the first line of defense against infection and tissue injury.

Question 8

What is the primary timing of defense for innate immunity?

Answer 8

Innate immunity provides an immediate response to tissue injury or infection, known as the inflammatory response.

Question 9

How does the timing of defense in adaptive (acquired) immunity differ from innate immunity?

Answer 9

Adaptive immunity has a delay between the primary exposure to an antigen and the maximal response, but it provides an immediate response upon secondary exposure to the same antigen.

Question 10

What is the specificity of the immune response in the innate immune system?

Answer 10

The immune response in innate immunity is broadly specific.

Question 11

What types of cells are involved in innate immunity?

Answer 11

Innate immunity involves cells such as epithelial cells, microbiome, mast cells, granulocytes (neutrophils, eosinophils, basophils), monocytes/macrophages, natural killer (NK) cells, platelets, and endothelial cells.

Question 12

Which cells are central to adaptive (acquired) immunity?

Answer 12

Adaptive immunity is primarily mediated by T cells, B cells, macrophages, and dendritic cells.

Question 13

Does innate immunity involve immunological memory?

Answer 13

No, innate immunity does not involve immunological memory.

Question 14

What active molecules are associated with innate immunity?

Answer 14

Innate immunity relies on active molecules such as defensins, cathelicidins, collectins, lactoferrin, and bacterial toxins.

Question 15

What are some components of protection in the innate immune system?

Answer 15

Protection in innate immunity includes anatomical barriers (e.g., skin and mucous membranes), cells, secretory molecules (e.g., lysozymes, low pH of stomach and urine), and ciliary activity.

Question 16

What are the key elements of protection in adaptive (acquired) immunity?

Answer 16

Protection in adaptive immunity involves activated T and B cells, cytokines, and antibodies as key components.

Question 17

What is the role of physical barriers in the first line of defense?

Answer 17

Physical barriers, such as the skin and linings of the respiratory, gastrointestinal, and genitourinary tracts, provide protection against damage and infection by pathogens.

Question 18

How are pathogens removed from the body when they attempt to breach physical barriers?

Answer 18

Mechanical processes in the body, such as coughing, sneezing, vomiting, or flushing by urine, help remove pathogens that try to breach physical barriers.

Question 19

What are some characteristics of the epithelial cells in the upper respiratory tract that aid in defense?

Answer 19

Epithelial cells in the upper respiratory tract produce mucus and have hair-like cilia, which trap and move pathogens upward. Coughing and sneezing then expel these trapped pathogens.

Question 20

How do temperature and pH contribute to inhibiting microorganisms in physical barriers?

Answer 20

Low temperature (such as on the skin) and low pH (such as in the skin and stomach) generally inhibit microorganisms because most pathogens require temperatures near 37°C (98.6°F) and a neutral pH for efficient growth.

Question 21

What are some substances secreted by epithelial cells to protect against infection?

Answer 21

Epithelial cells secrete substances like mucus, perspiration (sweat), saliva, tears, and earwax, which can trap potential invaders and contain microorganism-killing substances.

Question 22

What enzyme is found in perspiration, tears, and saliva that attacks the cell walls of Gram-positive bacteria?

Answer 22

These secretions contain lysozyme, an enzyme that attacks the cell walls of Gram-positive bacteria.

Question 23

How do sebaceous glands in the skin contribute to defense against microorganisms?

Answer 23

Sebaceous glands in the skin secrete fatty acids and lactic acid that can kill bacteria and fungi, creating an acidic and inhospitable environment for most bacteria.

Question 24

What are cathelicidins, and where are they produced?

Answer 24

Cathelicidins are antimicrobial peptides produced by epithelial cells of the skin, gut, urinary tract, and respiratory tract. They disrupt bacterial cell membranes, killing bacteria.

Question 25

What is the role of collectins, such as surfactant proteins and mannose-binding lectin, in the immune system?

Answer 25

Collectins react with carbohydrates on the surface of pathogens and help macrophages recognize and kill microorganisms. Mannose-binding lectin (MBL) activates the complement system, resulting in damage to bacteria or enhanced recognition by macrophages.

Question 26

What are human defensins, and how do they function?

Answer 26

Human defensins are antimicrobial peptides that exist as two subtypes, alpha and beta. Alpha-defensins work with neutrophils to kill bacteria, while beta-defensins are found in various epithelial cells and help protect against microorganisms.

Question 27

What is the pH range of the acidic environment created by sebaceous gland secretions in the skin, and why is it important?

Answer 27

The acidic environment created by sebaceous gland secretions has a pH range of 3 to 5. This acidity is important because it makes the environment inhospitable for most bacteria, inhibiting their growth.

Question 28

How do antimicrobial peptides like cathelicidins and defensins activate the immune system?

Answer 28

Antimicrobial peptides like cathelicidins and defensins can activate cells of the innate and acquired immune systems, helping to coordinate and enhance the immune response against invading microorganisms.

Question 29

What role does mannose-binding lectin (MBL) play in the immune system, and how does it recognize pathogens?

Answer 29

Mannose-binding lectin (MBL) recognizes a sugar commonly found on the surface of microbes. It is a powerful activator of the complement system, resulting in damage to bacteria or increased recognition by macrophages.

Question 30

What is the significance of surfactant proteins A through D in the context of collectins?

Answer 30

What is the significance of surfactant proteins A through D in the context of collectins?

Question 31

What are defensins, and what is their primary function in the immune system?

Answer 31

Defensins are antimicrobial peptides produced by various cells, including epithelial cells. Their primary function in the immune system is to defend against bacterial, fungal, and viral infections.

Question 32

What are the two main subtypes of defensins, and how do they differ in their activation requirements?

Answer 32

Defensins exist as two main subtypes: alpha-defensins and beta-defensins. Alpha-defensins often require activation by proteolytic enzymes, while beta-defensins do not require enzymatic activation.

Question 33

Which cells work in conjunction with alpha-defensins to combat bacterial infections?

Answer 33

Alpha-defensins work in collaboration with neutrophils to kill bacteria, particularly in areas of infection or inflammation.

Question 34

In which specific location in the body can alpha-defensins be found, and what is their role there?

Answer 34

Alpha-defensins are present in Paneth cells lining the small intestine. They protect against a variety of disease-causing microorganisms in the gastrointestinal tract.

Question 35

Where in the body are beta-defensins predominantly found, and what types of infections might they help protect against?

Answer 35

Beta-defensins are primarily found in epithelial cells lining the respiratory, urinary, and intestinal tracts, as well as in the skin. They contribute to protection against a range of bacterial, fungal, and viral infections, including adenovirus and human immunodeficiency virus (HIV).

Question 36

Besides their role in direct antimicrobial activity, how else do antimicrobial peptides like defensins contribute to the immune response?

Answer 36

Antimicrobial peptides like defensins can also activate cells of the immune system, helping to coordinate and enhance the overall immune response against invading microorganisms.

Question 37

What is the normal microbiome, and what was it previously known as?

Answer 37

The normal microbiome is an array of microorganisms that colonize the body’s surfaces. It was previously known as normal flora.

Question 38

Is the composition of the microbiome the same throughout the body, or does it vary?

Answer 38

The composition of the microbiome varies depending on the specific location in the body, such as the skin, mucous membranes of the eyes, upper and lower gastrointestinal tracts, upper respiratory tract, urethra, and vagina.

Question 39

How would you describe the typical relationship between microorganisms in the microbiome and the human body?

Answer 39

The microorganisms in the microbiome do not normally cause disease. Their relationship with humans is often commensal, benefiting one organism without affecting the other. However, it can also be mutualistic, benefiting both organisms.

Question 40

What are some of the ways in which the normal microbiome in the GI tract benefits the human body?

Answer 40

The normal microbiome in the GI tract benefits the body by (1) producing enzymes that aid in digestion and utilization of dietary molecules, (2) generating usable metabolites like vitamin K and B vitamins, and (3) producing antibacterial factors that prevent colonization by pathogenic microorganisms.

Question 41

How do members of the normal microbiome in the colon contribute to the prevention of pathogenic infections?

Answer 41

Members of the normal microbiome in the colon produce toxic chemicals and proteins, such as ammonia, phenols, indoles, and bacteriocins, which are toxic to pathogenic microorganisms. They also compete with pathogens for nutrients and block their attachment to the epithelium, a crucial step in the infection process for most pathogens.

Question 42

Where do most cells of the adaptive immune system reside in relation to the gut, and how does the gut microbiome affect them?

Answer 42

Most cells of the adaptive immune system reside in gut-associated lymphoid tissue. The gut microbiome influences the growth of this tissue and the development of both local and systemic adaptive immunity.

Question 43

What can happen when an individual undergoes prolonged treatment with broad-spectrum antibiotics?

Answer 43

Prolonged treatment with broad-spectrum antibiotics can alter the normal microbiome, reducing its protective activity and potentially causing an overgrowth of pathogenic microorganisms.

Question 44

Can you provide examples of microorganisms that may overgrow in response to prolonged antibiotic treatment in the intestine?

Answer 44

In the intestine, overgrowth of microorganisms like Candida albicans (yeast) or Clostridium difficile (a bacterium that causes pseudomembranous colitis, a colon infection) may occur in response to prolonged antibiotic treatment.

Question 45

How does the bacterium Lactobacillus contribute to the protection of the vaginal and urinary tracts in healthy women?

Answer 45

Lactobacillus, a major constituent of the normal gastrointestinal and vaginal microbiome in healthy women, produces various chemicals like hydrogen peroxide, lactic acid, and bacteriocins. These chemicals help prevent infections of the vagina and urinary tract by other bacteria and yeast.

Question 46

What is the potential risk associated with prolonged antibiotic treatment concerning Lactobacillus colonization?

Answer 46

Prolonged antibiotic treatment can diminish colonization with Lactobacillus in the microbiome, increasing the risk of urological or vaginal infections, such as vaginosis.

Question 47

How does the physical integrity of the skin and mucosal epithelium contribute to the maintenance of a mutualistic relationship with the microbiome?

Answer 47

The physical integrity of the skin and mucosal epithelium, along with other protective mechanisms, helps maintain a mutualistic relationship with the microbiome by preventing the immune and inflammatory systems from disrupting this relationship.

Question 48

What are opportunistic microorganisms, and when can they cause disease?

Answer 48

Opportunistic microorganisms are normally harmless members of the microbiome but can cause disease if an individual’s defenses are compromised or if there is a breach in the body’s protective barriers.

Question 49

Can you provide an example of an opportunistic microorganism and its protective role within the microbiome?

Answer 49

Pseudomonas aeruginosa, a member of the normal skin microbiome, produces a toxin that protects against infections with staphylococcal and other bacteria.

Question 50

Under what circumstances can severe burns lead to life-threatening systemic infections with Pseudomonas aeruginosa?

Answer 50

Severe burns can compromise the integrity of the skin, which may result in life-threatening systemic infections with Pseudomonas aeruginosa, as the protective barrier is compromised, allowing the microorganism to enter the body.