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Neural Biology 1 > immune system > Flashcards

immune system Flashcards

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1
Q

why do we need an immune system system ?

A

. an immune system is essential since we are constantly exposed to harmful microorganisms ( pathogens )
. pathogens vary in size and are constantly evolving

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2
Q

what does the immune system use to protect the body ?

A

the immune system uses a complex series of protective mechanisms ( cells, tissues and organs ) to control and eliminate these organisms

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3
Q

how does the immune system differentiate between the bodies own cells and foreign cells ?

A

. this is achieved through self marker molecules , known as major histocompatibility complex ( MHC ) associated with the surface of our own body
. therefore when the immune system encounters cells or organisms carrying foreign molecules it mounts an attack

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4
Q

what is antigen ?

A

. anything that triggers an immune response is called an antigen , which can be a microbe , part of a microbe or foreign cells or tissues

. e.g. if PX is giver the wrong blood type , the donor red cells , become foreign cells and are attacked

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5
Q

what are the variety of sizes that pathogens can have ?

A

. viruses : 10 to 1000 nm
. bacteria : 0.1 to 5 micrometers
. protozoa : 5 to 200 micrometer
. fungi : 3 micrometers to > 1 millimeter

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6
Q

what are different infectious diseases of the eye ?

A

. stye - bacterial infection of the small glands associated with eyelash follicles
. bacterial infection of the cornea - bacterial keratitis
. viral infection caused by virus called herpes simplex keratitis - same virus that causes cold sores
. infective conjunctivitis - which can be caused by a varity of pathogens mostly commonly bacteria and viruses
. acanthamoeba keratitis - protozoan infection of cornea - affects people wearing contact lenses

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7
Q

what are the different lifestyles of microbes ?

A

. viruses - intercellular infection - need to infect body cells for infection to hold ( also extracellular )
. bacteria - largely extra cellular ( some exceptions )
. protozoa - intercellular and extracellular
. fungi - extracellular
. immune system must deal with both intercellular and extracellular pathogens

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8
Q

what are the two overlapping compartments of the immune system ?

A
  1. innate system - first line of defence consisting of a series of physical barriers to prevent entry of pathogens , phagocytes to digest microorganism and chemical mediators to trigger recruitment and activation of immune cells which is referred to as inflammation
  2. adaptive system - is formed principally by lymphocytes ( T and B cells ) which contain specific receptors to recognise specific antigens associated with pathogens . also retains memory of previous encounter with the pathogen
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9
Q

explain the overview of the immune system ?

A
  1. innate system which consists of external defences and internal defences
  2. adaptive system which consists of antibody mediation - predominantly the role of B - lymphocytes and cell mediation - predominantly the role T - lymphocytes
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10
Q

what is the simplest way to avoid an infection ?

A

the simplest way to avoid infection is to prevent microorganism from gaining access to the body

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11
Q

what are the components of the first anatomical barrier ?

A

. the skin is an important barrier and is impermeable to most infectious agents

  • intact skin is very good barrier
  • cut in skin represents a portal in which microorganism can enter

. the skin also contains glands that produce acidic secretion inhibit bacterial growth due to low PH
- desquamation of skin cells removes potential pathogens

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12
Q

what are internal surfaces that are barriers to infection ?

A

. mucosal membrane - mucus secreted by membranes lining the inner surfaces of the body block the attachment of microbes to epithelial cells

. washing action of tears and urine also limit attachment

. many secreted fluids contain antibacterial components e.g. acid in stomach , lysozyme in tears and saliva
body fluids are usually antibacterial

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13
Q

what is mucus and what are some examples ?

A

. glycoprotein produced by goblet cells

. e.g. conjunctiva of eye , oral mucous , constantly washing of fluids over surface thus limiting attachment of microorganisms

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14
Q

what are non-pathogenic microorganisms ?

-non specific (inate) barriers to infection

A

. many non-pathogenic microorganism are present in the external and internal surfaces of the body where they compete for essential nutrients ( commensals
e.g yoghurt - compete with pathogens - probiotic yoghurt- contain live bacteria- replenish communal orgsanisms in gut and create a healthier environment in gut

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15
Q

what commensals ?

A

. healthy bacteria - compete in the gut with pathogens
. create much more healthy environment in gut
e.g yoghurt - compete with pathogens - probiotic yoghurt- contain live bacteria- replenish communal orgsanisms in gut and create a healthier environment in gut

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16
Q

what is the internal innate defense mechanism ?

A

. phagocytosis - phagocyte
- if microorganism penetrate the body can be destroyed by phagocytosis

  • phagocytes include the polymorphonuclear neutrophils and macrophages
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17
Q

what are neutrophils ?

A
  • neutrophils are the predominant which cell in the blood stream but can migrate into tissues during inflammation
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18
Q

what are macrophages ?

A

. macrophages differentiated from blood monocytes
. two types of macrophages mobile( able to move ) and fixed microphages
. mature macrophages settle in tissues where they are strategically places to intercept microbes - fixed
e.g. glial cells of retina in CNS, in run
. phagocytes bind to microorganisms , internalise and kill them

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19
Q

explain the process of phagocytosis ?

A

. phagocytes arrive at the site of inflammation by chemotaxis

. phagocytes attach to microorganism ( and other targets ) via surface receptors
-Pathogen engulfed by receptors on neutrophils

. microorganisms are then internalised ( phagosome - vacuole within cytoplasm) and destroyed by ( phagolysosome- where micro-organism is broken down )

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20
Q

summary of process of phagocytosis ?

A

. macrophages / neutrophils have receptors on surface for particular pathogen , then bind to pathogen , then engulf pathogen forming phagosome - a vacuole with cytoplasm , lysosomes then fuse with the phagosome to form phagolysosome

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21
Q

What is the role of a complement system?

A

. complement system comprises over 30 plasma and cell associated proteins which play an important role in the defence against pathogens particularly against bacteria

. activation of complement begins with recognition protein which bind to wide range of structures including pathogens or structures associated with cellular damage/derbis

22
Q

what is chemical component of the innate system?

A

. Complement system
. coordinated series of enzyme - catalysed reaction which provide a series of functions including the recruitment of phagocytes to sight of infection / injury

23
Q

what does complement system activation lead to ?

A

complement activation leads to a coordinates cascade of enzymatic cleavage events generating complement protein fragments that carry out particular functions

24
Q

what are the functions of complement system ?

A

. recruit phagocytes
. enhance phagocytosis ( opsonisation )
. membrane damage to foreign cells or microbes

25
Q

what are natural killer cells ?

A
  • they are the final component of innate system
  • small fractions ( 2% ) of the lymphocytes circulating in the blood are neither T cells or B cells
  • these are called natural killer cells because they are specialised to kill certain types of target cells
    e.g. viral infected cells and tumour cells
    . able to recognise own body cells through receptors on surface - inhibitory surfaces
    . when N-K cells are able to bind to self molecules , it recognises cell as normal cell
    . if self molecule is missing labels that service target will get destroyed
26
Q

why do we have the adaptive system as well as the innate system ?

A

. microorganisms develop strategies to evade our innate defence mechanisms
. the body has devised defence mechanisms which are tailored to deal with specific microbes
. these mechanisms have both specificity and memory

27
Q

what is the adaptive system primarily provided by ?

A

the cellular basis of specific immunity is provided by lymphocytes

28
Q

where do lymphocytes originate from ?

A

all lymphocytes originate from stem cells in bone marrow called lymphoid stem cells

29
Q

what are the two types of lymphocytes ?

A

. B cells - development occurs within the bone marrow - in some marrow lymphocytes develop into B cells
. T cells - leave the bone marrow develop in the thymus- thymus lymphocytes develop into T cells

30
Q

what are examples of primary lymphoid tissues ?

A

. both the bone marrow and thymus are examples of primary lymphoid tissues that are concerned with maturation and development of lymphocytes

31
Q

what do the bone marrow and thymus do ?

A

the bone marrow and thymus constitute primary lymphoid tissues where T and B cells differentiate into mature antigen recognising cells

32
Q

what are secondary lymphoid tissues ?

A

secondary lymphoid tissues are those in which lymphocyte activation , proliferation and differentiation occurs
e.g. lymph node , appendix, adenoid, tonsil

33
Q

how do lymphocytes recognise pathogens ?

A

. lymphocytes are responsible for recognising molecules of infecting pathogens ( antigens )

. lymphocytes have antigen receptors which recognise particular pathogens

34
Q

what are B cells concerned with ?

A

.B cells are concerned with the control of extracellular infections
. B cells use cell surface antibodies as antigen receptors
. each antibody molecule has two antigen receptors and antigen receptor is able to recognise a particular type of antigen
. each B cell molecule can only recognise one antigen

35
Q

what are T cells concerned with ?

A

T cells are concerned with intracellular infections
. T cells recognise antigens when they are presented to the receptor via MHC molecules
. each T cell can only recognise one particular antigen

36
Q

what is antigen ?

A

antigen is anything capable of activating the immune system

37
Q

what does a large lymphocyte population ensure ?

A

a large lymphocyte population ensures that an enormous range of antigens can be recognised by the body

38
Q

what does the immune system do following the first contact with pathogen ?

A

.following first contact with pathogen the immune system must expand the number of cells which recognise that pathogen

. following recognition of the pathogen the immune system must mount/ increase number of lymphocytes an appropriate response to eliminate it and minimise the damage it causes - cell division causes to increase number of lymphocytes which then differentiate into effector cells - which do the work.

39
Q

what is clonal section ?

A

. process of selection of the appropriate lymphocyte

40
Q

what is the function of memory cells ?

A

memory cells confer lasting immunity to the particular pathogen

41
Q

what are the 2 B cells response to antigen recognition ?

A

1-. antibody response which is mediated through B lymphocytes so when B cells recognise an antigen through antibody receptor on their cell surface , it transforms into antibody-producing cells ( plasma cells )
.2- proportion of activated B cells become memory cells that provide this enhance response such that the second response occurs rapidly
.

42
Q

why is there delay in antibody production following that initial primary antigen ?

A

the immune system is undergoing the clonal section , its identified the appropriate lymphocyte ,then there must be that cell division process that supplies a sufficient amount of B lymphocytes in order to get detectable levels of antibody .
. then we begin to get an initial antibody response through a particular subtype of antibody known as IGM , that’s followed by a secondary antibody response which is mediated by another antibody subtype known as IGG, when infection tails away the antibody also falls down .
. secondary antibody response has much shorter latency

43
Q

what is the antibody structure ?

A

. antibodies are tetrameric polypeptide structures
. 4 polypeptide chains - linked by disulfide bonds

. there is a region within the amino acid composition that is highly variable

. comprise 2 identical heavy chains and 2 identical light chains

. variable and constant domains

. the variable region- binding region ( termed FAB ) - where antibody recognises antigen
. variation in amino acid composition is to allow the variety of shapes of antigen binding site to encounter different shapes of antigen

. constant region ( Fc) component interacts with cell surface receptors and activates complement pathway-

44
Q

what are the 5 classes of antibodies ?

A

ig - immunoglobulin

. igG
.IgA
.IgM - 5 subunit 
.IgD
.IgE

larger antibody molecules particularly IgM is composed of whole series of antibody sub units

45
Q

what are the 4 principle functions of antibodies ?

A
  1. bind directly to pathogens preventing them from entering or damaging healthy body cells- important in defence against viruses -
  2. neutralise bacterial toxins- chemicals produced by bacterial cells
  3. activate complement
  4. facilitate phagocytosis by opsonization
46
Q

what is the T response ?

A

. T cells are responsible for cell-mediated immunity

.T cells include cytotoxic T cells and T helper cells which secrete cytokines ( chemical messengers )

. the T cell response consists of :
. antigen recognition

. activation signals - signals are predominantly coming from T helper cell

. cell division

47
Q

what is the process of antigen recognition be T cells ?

A

. T cells recognise antigens as peptide fragments which have come from inside cells

. cells present antigenic fragments ( peptide from cytoplasm ) on their surfaces for review by T-cells

. protein coded by a gene locus known as the MHC are involved in this process

. T cell is making decision about wether that particular pigment peptide fragment is part of normal body

48
Q

explain the contrast between the innate and adaptive components of immune system ?

A

INNATE

  • rapid response
  • anatomic barriers, phagocytes, chemical mediators
  • non-specific
  • no memory of previous encounter

ADAPTIVE

  • slow response
  • consists of B and T lymphocytes
  • highly specific
  • memory of previous immune response and maturation of response
49
Q

what is immunodeficiency ?

A

. immunodeficiency - can be congenital , so certain components of immune system may not develop - person is prone to infection
. can also be acquired
e.g. AIDS

50
Q

what happens when you have hyper reactive immune system ?

A

. immune system can be hyper reactive so immune system is very powerful
e.g. autoimmunity - immune system recognises self molecules as foreign and triggers destruction
. this can be a systemic autoimmune problem affecting lot of organ or organ specific e.g. autoimmunity within the thyroid gland which leads to reduction of thyroid hormones

51
Q

what balance do we have in the immune system

A

. immune system must not be overly reactive but also must have sufficient reactivity to deal with pathogen

52
Q

What are examples of fixed macrophages ?

A

microglia cells in CNS (brain and retina )

  • lungs- alveolar macrophages
  • liver- Kupffer cells

Neural Biology 1 (58 decks)

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