Immunity Flashcards
1
Q
the immune system
A
- combats infective agents
- recognises and rejects foreign cells and tissues
- specific and non-specific
2
Q
non-specific immune system (innate)
A
- first and second lines of defense
- primary defences
- skin
- mast cells + basophils
- histamine
- phagocytes
- complement proteins
- cytokines
- tears and mucus
3
Q
primary defences
A
- present from birth
- quick-acting
- effective against a wide range of pathogens and foreign substances
- always same response
4
Q
skin
A
- first natural barrier to infection
5
Q
mast cells and basophils
A
- large mobile cells
- release histamine
6
Q
histamine
A
causes inflammation response
7
Q
phagocytes
A
large white blood cells which engulf foreign substances
8
Q
complement proteins - general
A
blood proteins contributing to breakdown and removal of pathogens
9
Q
cytokines
A
small protein molecules
10
Q
tears and mucus
A
contain lysozymes
11
Q
histamines
A
- dilate arterioles
- cause diapedesis
- increase tissue fluid formation
- sensory neurones become more sensitive
- activates complement proteins in plasma
12
Q
complement proteins - specific
A
- attract phagocytes to site of reaction
- act as opsonins
- bind to, and form pores in, the surface of foreign cells
13
Q
monocytes
A
- loads!
- migrate into tissues
- mature into macrophages
- can renew lysosomes
14
Q
phagocytosis
A
1) phagocyte attracted to pathogen (due to chemical products of pathogen)
2) phagocyte CSM receptors attach to antigens on pathogen surface
3) pathogen engulfed to form phagosome
4) lysosomes move towards and fuse with phagosomes
5) lysozyme enzymes hydrolyse pathogen molecules
6) soluble products absorbed into cytoplasm or expelled from cell
15
Q
specific immune response (adaptive)
A
- blood and lymph cells and proteins that attack, disarm, destroy and remove foreign substances
- responds slowly
- only effective against specific pathogens
- activated by antigens
16
Q
B cells
A
- mature in bone marrow
- migrate to lymph nodes
17
Q
T cells
A
- mature in thymus gland
- migrate to lymph nodes
18
Q
immunological memory
A
immune response is sped up on repeated infection with the same pathogen
19
Q
antigens
A
- molecules recognised as non-self, that trigger a lymphocyte immune response
- complex of proteins or glycoproteins (each cell has several)
- also occur in non-cellular substances
20
Q
example of a non-cellular substances containing antigens
A
venom
21
Q
diapedesis
A
cells in capillary walls draw away from each other
22
Q
what does increased tissue fluid formation result in?
A
leucocytes, fluid, and antibodies increase in tissue
23
Q
what are the two sections of the specific (adaptive) immune response?
A
- humoural
- cell-mediated
24
Q
what are non-self antigens?
A
antigens from foreign organisms or substances to which the body has not yet become adapted
25
lymphocytes
- small leucocytes with little cytoplasm and spherical nuclei
- originate from stem cells in the bone marrow
- circulate in the lymph once mature
- only activated by specific antigens
26
lymphatic system
- nodes, spleen, adenoids, tonsils + bloodstream
| - contains lymph
27
humoural response
uses soluble antibodies in the blood and lymph
28
antibody
- a unique globular protein that reacts with a specific membrane-bound antigen
- binding only occurs with complementary shape
- produced by small lymphocytes
29
In the humoural response, several types of reaction occur...
... depending on the ability of the antibody to bind to the antigen
30
which small lymphocytes produce antibodies?
B cells
31
B cells
- already exist in millions
- countless types, each of which produce a specific antibody
- mature in the bone marrow
- have immunocompetence, and self detection
- produce memory cells
32
when a B cell meets an antigen
- it divides mitotically (clonal selection)
| - after several generations, the cells differentiate into plasma cells
33
plasma cells
- all formed from one type of B cell
- all secrete the same antibody
- lots of RER, Golgi and mitochondria
34
primary response
- the response of the immune system to an antigen it meets for the first time
- slow; takes days or weeks to recruit enough plasma cells to control infection
35
secondary response
- involves memory cells
| - rapid man
36
antibody structure
- protein
- 4 polypeptide chains (quaternary structure)
- 2 light chains
- 2 heavy chains (long)
- disulphide bridges join light and heavy chains
- constant region (same AAs)
- variable region
- hinge region
37
variable region
- variety of AAs
- antigen binding site
- causes antibody specificity
38
How do antibodies trigger pathogen destruction?
1) agglutination
2) opsonisation
3) neutralisation
39
agglutination
- binding of antibodies causes pathogens to clump together
- helps prevent spread
- makes engulfing easier
40
opsonisation
- acts as an opsonin
41
opsonin
a chemical which makes the pathogen more easily recognised by phagocytes
42
neutralisation
- antibodies neutralise the effects of bacterial toxins by binding to them
43
How do antibodies tackle viruses?
bind to them, stopping them from attaching to the host
44
immunoglobins
- glycoprotein receptors on B cell membranes
- B cells contain multiple copies of immunoglobin genes
- genes recombine randomly during maturation, producing new unique genes for immunoglobin specificity
45
cell-mediated response
- occurs when pathogen is inside cell (mostly viral)
- when cells have become antigen presenting
- produces cells specific to invading pathogen
46
How are antigen presenting cells (APCs) produced?
- during infection, pathogen is digested
| - antigens are bound to MHC (locus of DNA)
47
T-helper cells
- have particular receptor proteins on cell surface membrane, specific to antigen
- on meeting, cell divides mitotically
- some cells remain in blood and lymph as memory cells, others activate immune cells
48
Which immune cells to T-helper cells activate?
- B cells
- phagocytes
- Tc (cytotoxic T) cells
- macrophages
- Ts (suppressor T) cells
49
T-killer cells
- have complementary antigen-receptors
- attack cells that have been antigenically altered or larger pathogens
- produce perforin
50
describe a large pathogen
e.g. a unicellular parasite
51
perforin
punches holes in CSM
52
T-suppressor cells
- suppress immune responses where appropriate
| - interact in antigen-specific manner with Th or B cells
53
macrophages
- large phagocytotoxic white blood cells which destroy pathogens
- derived from monocytes
- have indented nuclei
54
immune communication
necessary because humoural and cell-mediated response work in conjunction
55
cytokines
- activators or inhibitors of cell signalling pathways
- growth, differentiation and behaviour of cells
- e.g. interferons
56
interferon-alpha
- regulates growth genes
| - used in medicine: boosts immune system and reduces tumour growth
57
monoclonal antibodies - basic
a single type of antibody produced by a B cell in response to a specific antigen that can be isolated and cloned
58
monoclonal antibodies - specific
- cloned B cell stimulated with an antigen epitope, fused with immortal malignant antibody-producing myeloma cell; hybridoma cell
- can multiply specifically and infinitely
59
general principles of monoclonal antibody use:
- attach to fluorescent dyes/radioactive labels
- also agglutinate antigens
- shows presence and extent of infection
60
pregnancy testing - how they work:
- monoclonal antibodies correspond to coloured particles (blue latex)
- hcG binds to particles
- hcG-antibody-colour complex moves along strip
- captured (immobilised) by another antibody to form a line
61
pregnancy testing - in general:
- done at home
- non-invasive
- reallllly early indicator
62
how is a pregnancy test a really early indicator?
placenta produces human chorionic gonadotrophin (found in mother's urine) when fertilised egg binds to uterine wall
63
HSV1 testing
(3-G11) reacts with glycoprotein C complex
64
HSV2 testing
- 6-A6
- 6-E12
- 6-HII
65
herpes testing allows
serotyping - classification based on surface antigens
66
HIV testing - ELISA
- HIV p24 antigens manufactured and attached to petri dish
- wash with blood sample
- wash unattached antibodies away
- wash with marker antibody (specific to all human antibodies)
67
describe the marker antibody in the ELISA test
- black circle
| - enzyme + substrate
68
separation of monoclonal antibodies
- antibodies immobilised on resin beads
- mixture poured over beads
- only target molecules attach
- beads washed with substance that releases the molecule
69
ELISA
enzyme-linked immunoabsorbant assay
70
ADEPT acronym
antibody direct enzyme prodrug therapy
71
ADEPT
- enzyme is attached to monoclonal antibody
- activates a drug (cytotoxic)
- attaches to target cancer cells
- large amount of inactive drug injected
- prodrug remains inactive around healthy cells
72
treating cancer with ADEPT
- suicidal protein caused by contact inhibition allows specificity to cancer cells
- stops blood vessel formation around tumours
- tag with cytotoxic drug
73
suicidal protein
blocks mitotic signals
74
Limitations of monoclonal antibodies
- ethics: humans cannot be immunised against antigens
- fused human lymphocyte-mouse myeloma cells are very unstable (recognised as foreign and eliminated)
- no suitable human myeloma cells to replace mouse
- antigenic variability -> mutation
75
ethical issues with monoclonal antibodies
- mice used to produce antibodies and tumour cells involves spleen removal and emulsification
- deaths associated with MS treatment
- trial for TGN1412 - 6 patients had multiple organ failure (they survived)
76
Why did the patients on the TGN1412 trial have multiple organ failure?
T cells produced chemicals overstimulating the immune response and attacked body tissue
77
advantages of monoclonal antibodies
- can target any molecule (including human ones)
- don't kill adjacent cells
- produced in vast quantities, quickly
78
uses of monoclonal antibodies
- cancer treatment
- prevention of transplant rejection
- auto-immune treatment
- viral treatment
79
vaccinations
- artificial active immunity
80
active immunity
- delay between infection and full immune response
| - vulnerable to toxins
81
attenuation
- weakening of pathogens
| - culturing anaerobically away from temperature optimum
82
toxoids
- inactivated toxins
| - no deleterious side-effects
83
herd immunity
- vaccinations administered to a large number of people at the same time
- results in general immunity
- reduces risk of encountering an infectious agent
84
why might vaccines be ineffective?
- inherited defective immune system
| - defences weakened by infections/malnutrition
85
antigenic drift
small changes in pathogen antigens
86
antigenic shift
large changes in pathogen antigens
87
artificial passive immunity
ready-made antibodies against a toxin
88
natural passive immunity
- occurs when a fetus is still in the uterus
- maternal antibodies cross the placenta into fetal blood
- temporary; antibodies broken down by spleen and liver
- no immunological memory
89
what does natural passive immunity not give any immunological memory
because the baby did not make the antibodies itself
