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Immunology > Innate Immunity > Flashcards

Innate Immunity Flashcards

1
Q

What are the different types of pathogens ?

A
  • bacteria
  • fungi
  • protists e.g. parasite
  • viruses
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2
Q

What are the different ways in which pathogens can enter the body ?

A
  • breaks in the skin
  • lungs
  • digestive tract
  • urogenital system
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3
Q

What is the largest organ of the body ?

A

The skin

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4
Q

How can pathogens move around the body ?

A

Via the circulatory system or the lymphatic system

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5
Q

What are the 2 phases of innate immunity ?

A

1) innate phase
2) early-induced phase

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6
Q

Describe the innate phase of innate immunity

A
  • immediate action
  • preformed mediators kill and weaken pathogens
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7
Q

Describe the early-induced phase of innate immunity

A
  • sensing of threat
  • recruitment of cells and mediators
  • inflammation
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8
Q

What are some of the physical barriers of the immune system ?

A
  • skin
  • mucus
  • epithelia
  • stomach
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9
Q

What are some of the chemical barriers of the immune system ?

A
  • coughing and sneezing
  • the body creates hostile environments for pathogens to survive e.g. stomach acid and urine
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10
Q

How do pathogens exit the body ?

A

The flow of bodily fluids such as urine will cause pathogens to exit the body

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11
Q

What is found in tears and sweat that helps the breakdown of pathogens ?

A

Lysozyme enzymes in tears and sweat help to dissolve bacterial cell walls

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12
Q

What covers all body surfaces ?

A

Epithelial cells

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13
Q

Describe how microbes are removed from the skin

A

There is a longitudinal flow of air and fluid across the surface of the skin to remove microbes from the surface of the skin

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14
Q

Describe the structure of skin

A
  • it is made up of multiple layers of epithelial cells
  • the dead outer layer of keratinised epithelium is constantly shedding and so any microbes present are shed
  • the skin contains :
    • lamella bodies of fatty acids which create a waterproof barrier
    • alpha and best defending which create the body’s own anti microbial
    • S100 proteins e.g. psoriasin and calprotectin which target any pathogens which could breach the outermost layer
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15
Q

Describe how the stomach is involved in the removal of pathogens

A
  • has a low pH which creates a relatively sterile environment
  • contains digestive enzymes which digest microbial proteins and degrade them
  • muscular contractions move fluid in and out creating a mechanical flow
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16
Q

Describe how the small intestine is involved in the breakdown and removal of pathogens

A
  • it has a slightly pH than the stomach which means the antimicrobial peptides can work better
  • contains digestive enzymes
  • the flow of fluid will flush organisms out
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17
Q

Describe how the large intestine is involved in the breakdown and removal of pathogens

A
  • the stable microbiome produces its own antibiotics
  • the expulsion of faeces removes pathogens
18
Q

What is the importance of the flow of fluid from the stomach to the large intestine ?

A

It prevents microbes from settling and colonising in the body

19
Q

Describe how pathogens are broken down and removed from the airways

A
  • there is mechanical flow of air in the lungs through coughing and sneezing
  • the coordinated movement of cilia in the mucociliary escalator will move mucus and foreign particles up the airway
  • alveolar macrophages perform phagocytosis of pathogens
  • surfactant proteins such as SP-A and SP-D aid the alveolar macrophages by marking pathogens
20
Q

What is the function of antimicrobial peptides and mucins ?

A

They provide a protective barrier against pathogens

21
Q

How do glands protect against pathogens ?

A
  • lacrimal glands produce tears and these contain lysozymes
  • salivary glands produce saliva, lactoferrin, lysozymes and antibodies
  • mammary glands produce calprotectin, lactoferrin and antibodies
22
Q

Describe the function of epithelial cells in protecting against pathogens

A

Epithelial cells are tightly packed together by tight junctions, adherens junctions and desmosomes providing a strong barrier against pathogens

23
Q

How do epithelial cells protect against pathogens ?

A
  • epithelial cells are synthetic and produce a range of antimicrobial peptides, mucins and soluble mediators e.g. cytokines and chemokines
  • they are involved in the recruitment of leukocytes from the blood to sites of infection and inflammation
  • they use PAMP receptors to detect sites of microbes
24
Q

Why is the cellular response of the innate response activated ?

A

When the physical and chemical barriers of the innate response are breached the cellular response will be activated

25
Q

Which cells are the main cells involved in the cellular innate response ?

A
  • the granulocytes of the myeloid lineage of haematopoietic stem cells : neutrophils, eosinophils, basophils and mast cells
  • natural killer cells of the lymphoid lineage
26
Q

Describe the function of neutrophils

A
  • more than 60% of blood leukocytes are neutrophils
  • they are recruited to tissues after receiving signals from the inflammatory response
  • they carry out phagocytosis
  • if infected by fungi and bacteria there will be high levels of neutrophils in the blood
27
Q

Describe the function of eosinophils

A
  • less than 5% of blood leukocytes are eosinophils
  • they are tissue resident cells and maintain tissue homeostasis
  • they defend against parasites
  • they are involved in the allergy response
28
Q

Describe the function of basophils

A
  • less than 1% of blood leukocytes are basophils
  • defend against parasites
  • they are involved in regulating the immune system
29
Q

What do the granules of neutrophils contain ?

A
  • mostly contain enzymes and other substances used to disrupt pathogens
  • lysozymes
  • lactoferrin
30
Q

What do the granules of eosinophils contain ?

A
  • preformed proteins
  • cytokines
  • chemokines
  • growth factors
31
Q

What do the granules of basophils contain ?

A
  • preformed proteins
  • cytokines
  • chemokines
  • growth factors
  • active mediators e.g. histamine
32
Q

Describe how neutrophils work

A

1) neutrophils are recruited to the site of infection by chemokine trail
2) once they are in the tissue they carry out phagocytosis

33
Q

Describe how eosinophils work

A
  • they release their granular components into the surrounding area
  • maintain homeostasis in the intestines, uterus, lungs and thymus
34
Q

What are the 4 ways in which eosinophils release their granules ?

A
  • classical exocytosis
  • compound exocytosis
  • piecemeal degranulation
  • cytolysis
35
Q

Describe the function of mast cells

A
  • they are tissue resident cells
  • they are granulocytes and when activated release their granules in the surrounding area
  • they are not polymorphonuclear
  • they release active mediators e.g. histamine
  • initiate the inflammatory response
36
Q

Describe the function of monocytes

A
  • they are blood born and make up 2-10% of blood leukocytes
  • their main roles are phagocytosis and bacterial killing in blood
37
Q

Describe the function of macrophages

A
  • macrophages are differentiated monocytes
  • they can either be tissue resident or inflammatory
  • tissue resident macrophages populate almost every tissue in the body
  • inflammatory macrophages undergo changes in size, phagocytic ability, complexity of organelles and hydrolytic enzymes as they enter tissues
38
Q

Describe the function of dendritic cells

A
  • they are tissue resident cells
  • make up a tiny percentage of blood
  • act as guardians at potential entry points for microbes
  • carry out phagocytosis and do antigen presentation
  • link the innate and adaptive immune system
39
Q

Describe the function of natural killer cells

A
  • large granular cells that target virally infected or cancer cells
  • make up 5-10% of circulating lymphocytes
  • release cytotoxic chemicals when in cell to cell contact
  • have immunoregulatory effects
40
Q

Describe now natural killer cells work

A
  • if there is a balance of activation and inhibition signals then nothing will happen and the natural killer cell will dissociate
  • if the inhibitory signal is lost :
    1) the natural killer cell is activated
    2) cytokines are released
    3) perforin is released
    4) cytolysis of infected cells
41
Q

Describe the function of innate lymphoid cells

A
  • have 3 main families : ILC1, 2 and 3
  • have a role in barrier homeostasis
  • implicated in barrier disorders e.g. eczema

Immunology (8 decks)

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