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Introduction to medicine (Year 1) > Introduction to immune response > Flashcards

Introduction to immune response Flashcards

- Describe the importance of both innate and adaptive immune systems - **Describe the differences between innate and adaptive immune systems naming the cells and molecules involved in each** - **List and describe the role of innate protective factors acting as barriers to infection** - **Describe the function of T lymphocytes** - **Describe the function of B lymphocytes** - **Define phagocytosis and describe the function of phagocytic cells.** - **Describe the characteristics of the main phagocy

1
Q

What is the innate immune response?

What type of response does it induce?

A

Innate immune response is the immune response we are born with.

It produces a non-specific response

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2
Q

What are the chemical and physical barriers that repel pathogens in the innate immune system?

A
  • Chemical barriers- lysozyme (tears), low stomach pH creating acidic environment
  • Physical barriers- Epithelium (skin/gut), cilia lining airways
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3
Q

How does lysozyme acts as a barrier to infection?

A
  • It acts as a mechanism to kill bacteria by hydrolysing their peptidoglycan cell walls , so it’s especially effective against gram-positive bacteria
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4
Q

How does low stomach pH act as a barrier to infection?

A

The low pH kills most microorganisms that are ingested

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5
Q

What are the key features of the innate immune system?

A
  • Non-specific cells that do not distinguish invaders
  • Response occurs within minutes-hours
  • No memory cells
  • Always respond to pathogen in the same manner
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6
Q

Define phagocytosis

A

The ingestion of bacteria or other pathogens by phagocytes

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7
Q

What cells are phagocytes?

A

Monocytes
Macrophages
Neutrophils
Basophils
Eosinophils
Mast cells
Dendritic cells

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8
Q

What is the function of monocytes?

A

Monocytes reside in blood and tissues to find and destroy pathogens, and eliminate infected cells

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9
Q

What is the function of macrophages?

A

Recognise pathogen and activate innate immune system

Destroy infectious organisms that enters the body, clear cellular debris and wound healing

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10
Q

What is the function of neutrophils?

A

Cells that travel to site of infection, where they destroy microorganisms by ingesting them and releasing enzymes that kill them (phagocytosis)

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11
Q

What is the function of basophils?

A
  • Immune surveillance
  • Play key role in response to allergies - release histamine which enlarges blood blood vessels to improve blood flow and heal affected area
  • Histamine also allows other cells to quickly target and respond to allergen
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12
Q

What is the function of eosinophils?

A
  • Active pathogenic role in inflammation associated with allergic disorders.
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13
Q

What is the function of mast cells?

A

Contain chemicals such as histamines, heparin, cytokines that play a role in immune restore to certain bacteria and parasites, and other types of immune response

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14
Q

What is the function of dendritic cells?

A
  • They capture, process and present antigens from pathogen to immune cells (T and B cells) and mediate their polarisation into effector cells, therefore these activate the specific (adaptive) immune system
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15
Q

What are the 4 stages of phagocytosis?

A

Stage 1 - Recognition of the target particle (opsonisation) and chemotaxis
Stage 2 - Signalling to form phagosome
Stage 3- Phagolysosome formation
Stage 4- Oxidative burst

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16
Q

Explain the first stage of phagocytosis, recognition of the target particle and chemotaxis

A
  • Pathogens release inflammatory mediators (inflammatory cytokines, complement proteins etc), called Pathogen Associated molecular patterns (PAMPs)
  • Resting phagocytes have pattern recognition receptors (PRRs) that identify PAMP and are activated by these , resulting in circulating phagocytes producing surface glycoprotein receptors, increasing their ability to adhere to inner surface of capillary walls, and move to the site of infection (this is chemotaxis).
  • Receptors on the plasma membrane of phagocytes can release opsonin, which coats cells or pathogens so phagocytes become attracted to them (opsonisation)
17
Q

Explain the second stage of phagocytosis, signalling to form phagosome

A
  • Phagocytic receptors initiate signalling cascades that remodel lipids in the cell membrane and regulate the actin cytoskeleton to extend the cell membrane around the pathogen
  • Phagocytic receptors engage in a sequential order and cooperate to complete the formation of the phagosome
18
Q

Explain the third stage of phagocytosis, phagolysosome formation

A
  • The phagosome fuses with lysosomes
  • The membrane changes its membrane composition and contents to turn into a phagolysosome, a vesicle that can release digestive lysosomes to destroy the pathogen. This transformation is phagosome maturation.
  • Phagosome maturation consists of successive fusion and fission interactions between the phagosome and endosomes, late endoscopes and finally lysosomes to become a phagolysosome. This is because the phagosome fuses with lysosomes when it becomes a late stage phagosome through interaction with endoscopes.
  • At the end, the phagolysosome has a different membrane composition, as granules from lysosomes contain a very acidic and degradative environment, which allows it to kill and digest pathogens

After the pH is sufficiently lowered, azurophilic granules are activated and kill more pathogens

19
Q

Explain the fourth stage of phagocytosis, phagolysosome maturation

A

NADPH oxidases oxidise O2 molecules, creating superoxide ions. The ions are converted by superoxide dismutate into H2O2, which then destroys remaining pathogens

  • Continues to swallow pathogens before oxidative burst-> Produces highly reactive oxygen e.g. H2O2; destroys proteins, nucleic acids, killing pathogens and the phagocyte
20
Q

How does phagocytosis remove dead cells?

A
  • Dying cells secrete a ‘find me’ signal, and they expose this signal on their surface.
  • Phagocytes ingest the dead cells, direct them to lysosomes, and degrade their cellular components into basic biochemical building blocks: amino acids, nucleotides, fatty acids, and monosaccharides.
  • These molecules will be released from the lysosomes and reused to make new macromolecules
21
Q

What are the cell types in the adaptive immune response?

A
  • T helper cells
  • Cytotoxic T cells
  • B cells
  • Plasma cells
22
Q

What are the functions and properties of T helper cells?

A
  • Involved in cell-mediated response
  • Recognises antigens presented by MHC class II molecules
  • Expresses CD4, CD3, TCR, CD28
  • Major source of IL-2
  • Mediates acute and chronic organ rejection
23
Q

What are the functions and properties of Cytotoxic T cells?

A
  • Involved in cell-mediated response
  • Recognises antigens presented by MHC class I molecules
  • Induce apoptosis in virally infection and tumour cells
  • Expresses CD8
  • Also expresses CD3, TCR
  • Mediates acute and chronic organ rejection
24
Q

What are the functions and properties of B cells?

A
  • Major cell of humoral immune response
  • Acts as an antigen presenting cell
  • Mediates hyperacute organ rejection
25
Q

What are the functions and properties of plasma cells?

A
  • Differentiated from B cells
  • Produces large amounts of antibody specific to a particular antigen
26
Q

What is the function of T lymphocytes?

A
  • T lymphocytes increase apoptosis to destroy cells that have been hijacked by viruses and pathogens
27
Q

What is the function of B lymphocytes?

A
  • B cells release antibodies used to attack invading pathogens
28
Q

What are the 2 primary lymphoid organs?

A

Bone marrow
Thymus

29
Q

Define secondary lymphoid organs?

A

Organs where lymphoid cells fight microbes

Introduction to medicine (Year 1) (59 decks)

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