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Biomedical Science (Y1a) > Ch1 > Flashcards

Ch1 Flashcards

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1
Q

What is the function of an immune system?

A
  • to defend against foreign invaders by generating a coordinated immune response
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2
Q

What are the types of immune systems?

A
  • innate (non-specific)
  • adaptive (specific)
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3
Q

What are the types of antigens?

A
  • toxins
  • pollution
  • bacterial
  • virus
  • parasite
  • fungi
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4
Q

What is the function of innate immune system?

A
  • to provide first line defence against pathogens
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5
Q

What are the characteristics of innate immune system?

A
  • non-specific
  • no memory
  • in-born
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6
Q

What are the types of defence barriers in innate immune system?

A
  • physical
  • chemical
  • physiological
  • phagocytic
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7
Q

What are the physical defence barriers in innate immune system?

A
  • respiratory tract
    => nasal hair –> remove inhaled particles
    => mucosal membrane and mucus –> mucosa secretes mucus which trap microbes –> microbes are removed by the beating of cilia on the epithelial cells, coughing and sneezing
  • skin
    => outer layer of dead skin with waterproof keratin protein –> prevent penetration of microbes
  • body fluids
    => urine and sweat can flush out microbes by the physical movement
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8
Q

What are the chemical defence barriers in innate immune system?

A
  • lysozyme (digestive enzyme)
    => present in tears and saliva
    => digest bacterial cell wall –> bacterial cell will soon lysed
  • sebum
    => secreted by sebaceous gland
    => unsaturated fatty acids inhibit the growth of bacteria and fungi due to a slightly acidic environment
    => over-production –> clog or block follicles –> inflammation –> pimple
  • acid
    => HCI in urine (uric acid), stomach (gastric acid) and vaginal secretion (lactic acid) –> acidic environment inhibit the growth of bacteria
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9
Q

What are the physiological defence barriers in innate immune system?

A
  • temperature
    => fever inhibit the growth of some pathogens and stimulate killer T cells which target virus-infected/abnormal/cancer cells
  • pH
    => low pH in stomach kills most microbes and destroy their toxins as it will be denatured under extreme pH
    => rapid pH change from the stomach to the upper intestine (2–>8)
  • normal flora
    => non-pathogenic bacteria lives on mucosal surface –> compete nutrients and attachment sites on epithelia –> pathogens have lower chance to survive
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10
Q

How to identity chemical and physiological barrier?

A
  • chemical is the acid itself while physiological is the acidic environment
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11
Q

What are the major types of immune cells which contribute to WBC?

A
  • lymphocytes
  • phagocytes
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12
Q

What are the types of phagocytic cells in innate immunity?

A
  • neutrophils
  • monocytes (macrophages)
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13
Q

Describe neutrophils and its function.

A
  • most abundant kind of WBC
  • granulocytes circulating in the blood
  • move quickly to the infection sites and engulf pathogens
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14
Q

What are the functions of monocytes/ macrophages?

A
  • able to present antigen on cell surface
  • activate T cells and immunity
  • engulf dead cells and microbes
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15
Q

How do phagocytes migrate to the site of infection?

A
  • ameboid movement –> diapedesis (phagocytes squeeze to migrate out of blood vessels)
  • chemotaxis –> phagocytes move towards microbes due to the attraction of chemotaxins (histamine)
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16
Q

What are the stages of phagocytosis?

A
  • attachment
    => phagocytes bind to microbes via their cell surface receptors
  • ingestion
    => microbes are injected by membrane invaginations (pseudopodia) and enclosed by phagosome
  • killing
    => lysosome fuse with phagosome forming phagolysosome –> release digestive enzymes –> microbes are killed
  • degradation
    => microbes are digested inside the phagolysosome –> digested products are released by exocytosis
17
Q

When is adaptive immune system necessary and why does it develop?

A
  • when innate defence mechanisms fail to stop the pathogens
  • it develops due to the exposure to various antigens
18
Q

How does adaptive immune system work and what is the function of it?

A
  • works in antigen-specific manner to eliminate the antigen and provide prolonged protection for future challenge
19
Q

What are the characteristics of adaptive immune system?

A
  • specific –> specialised response for best protection
  • diverse –> protection against various pathogens
  • memory –> enhanced response with repeated exposure
  • self and non-self discrimination –> lower autoimmunity
20
Q

What is the common morphology of lymphocytes (B and T cells)?

A
  • big, round nucleus centered in the cell
21
Q

What are the major components of adaptive immune system?

A
  • antigen-presenting cells (macrophages, B cells and dendritic cells)
  • lymphocytes (B and T cells)
22
Q

What is the use of antigen-presenting cells?

A
  • to activate T cells
23
Q

What are the types of adaptive immunity?

A
  • active natural –> infection
  • passive natural –> transfer of antibodies from mother to foetus via placenta
  • active artificial –> vaccination
  • passive artificial –> injection of ready-made antibodies
24
Q

How to identify between active, passive and artificial?

A
  • active –> produce own antibodies
  • passive –> receives ready-made antibodies
  • artificial –> injection
25
Q

How adaptive immunity is mediated?

A
  • by humoral (antibodies) and cell-mediated (T cells) response
26
Q

How is humoral immune system mediated and what is the function of the response?

A
  • mediated by antibody secreted by B cells from bone marrow to defend against threats outside the cell
27
Q

What is the process of humoral immune response?

A
  • B cells express specific cell surface Ab molecules –> bind to extracellular antigens –> activated B cells differentiate into plasma cells –> production of Ab
28
Q

Why are antigen-presenting cells essential?

A
  • essential for activation of T cells
29
Q

How is cell-mediated immune response mediated? How does it work?

A
  • mediated by T cells from thymus
  • T cells express specific T-cell receptor –> bind to Ag presented by antigen-presenting cells on MHC I or MHC II
30
Q

What are the types of cell-mediated immune response?

A
  • (stronger) extracellular Ag on MHC II
    => lysosome digest pathogen into pieces –> MHC II takes the antigen fragment and presents it on the cell surface –> helper T cells are activated and secrete cytokines that stimulate B cells to differentiate into plasma cells and memory B cells and simulate cytotoxic T cells and natural killer cells to kill virus-infected/ abnormal or cancer cells
  • (weaker) intracellular Ag on MHC I
    => MHC I bind to the Ag in cells and present it on the cell surface –> stimulate cytotoxic T cells to kill virus-infected/ cancer/ abnormal cells
31
Q

Why do the effector cells able to response to cytokines secreted by helper T cells?

A
  • cytokine receptors are present on the surface of effector cells –> able to receive the stimulation from cytokine and release cytotoxic molecules including digestive enzyme
32
Q

Compare innate immunity and adaptive immunity in terms of six perspectives.

A

(innate vs adaptive)
- specificity –> low vs high
- diverse –> low vs high
- memory –> no vs yes
- effector cells –> phagocytes, Nk cells vs lymphocytes
- molecules –> digestive enzyme vs antibodies and cytokines)
- response time –> quick vs slow

33
Q

Where are the cells of the immune system originated from? What are the two lineages?

A
  • hematopoietic stem cells in the bone marrow
  • lymphoid stem cells and myeloid stem cell (NK, dendritic cells, neutrophils and monocytes)
34
Q

What are the examples of lymphoid and myeloid stem cells?

A
  • lymphoid stem cells –> NK, B, T, dendritic cells
  • myeloid stem cells –> monocytes, mast cells, neutrophils, eosinophils, basophils, platelets and RBC

Biomedical Science (Y1a) (12 decks)

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