1
Q
What is the function of an immune system?
A
- to defend against foreign invaders by generating a coordinated immune response
2
Q
What are the types of immune systems?
A
- innate (non-specific)
- adaptive (specific)
3
Q
What are the types of antigens?
A
- toxins
- pollution
- bacterial
- virus
- parasite
- fungi
4
Q
What is the function of innate immune system?
A
- to provide first line defence against pathogens
5
Q
What are the characteristics of innate immune system?
A
- non-specific
- no memory
- in-born
6
Q
What are the types of defence barriers in innate immune system?
A
- physical
- chemical
- physiological
- phagocytic
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
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
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
10
Q
How to identity chemical and physiological barrier?
A
- chemical is the acid itself while physiological is the acidic environment
11
Q
What are the major types of immune cells which contribute to WBC?
A
- lymphocytes
- phagocytes
12
Q
What are the types of phagocytic cells in innate immunity?
A
- neutrophils
- monocytes (macrophages)
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
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
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)
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
How adaptive immunity is mediated?
- by humoral (antibodies) and cell-mediated (T cells) response
26
How is humoral immune system mediated and what is the function of the response?
- mediated by antibody secreted by B cells from bone marrow to defend against threats outside the cell
27
What is the process of humoral immune response?
- B cells express specific cell surface Ab molecules --> bind to extracellular antigens --> activated B cells differentiate into plasma cells --> production of Ab
28
Why are antigen-presenting cells essential?
- essential for activation of T cells
29
How is cell-mediated immune response mediated? How does it work?
- 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
What are the types of cell-mediated immune response?
- (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
Why do the effector cells able to response to cytokines secreted by helper T cells?
- 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
Compare innate immunity and adaptive immunity in terms of six perspectives.
(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
Where are the cells of the immune system originated from? What are the two lineages?
- hematopoietic stem cells in the bone marrow
- lymphoid stem cells and myeloid stem cell (NK, dendritic cells, neutrophils and monocytes)
34
What are the examples of lymphoid and myeloid stem cells?
- lymphoid stem cells --> NK, B, T, dendritic cells
- myeloid stem cells --> monocytes, mast cells, neutrophils, eosinophils, basophils, platelets and RBC
Biomedical Science (Y1a)
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