Immune System Flashcards
1
Q
What are microbes?
A
bacteria, fungi, viruses, parasites
2
Q
What are non-microbials?
A
pollen, insect venom, transplanted organs
3
Q
What are inert substances?
A
dirt and wood
4
Q
What are antigens?
A
- substances foreign to the host which can stimulate an immune response
- examples include bacteria, pollen, etc.
- also know as immunogens
5
Q
What is an epitope?
A
the discrete immunologically active sites on antigens
• the portion of the antigen that interacts with the antibody
• a single antigen may have multiple antigenic determinants, each of
which is capable of activating a distinct clone of T and B cells
6
Q
What are Major Histocompatibility Complex (MHC) molecules?
A
self recognition molecules (glycoproteins) located on the surface of all
nucleated cells
- unique for each person
7
Q
Where are Class I MHC molecules found?
A
on all nucleated cells
8
Q
Where are Class II MHC molecules found?
A
only on macrophages and B lymphocytes
9
Q
What are cytokines?
A
• small proteins produced during an immune response which regulate the movement, proliferation,
and differentiation of leukocytes and other cells
• chemical messengers
10
Q
What are cytokines (chemical messengers) made by?
A
made by helper T cells, macrophages, and other cells such as fibroblasts
11
Q
Examples of cytokines
A
interleukins
• interferons (α, β, γ)
• tumor necrosis factor (TNF)
• colony stimulating factors
12
Q
Which cell types involved in the immune response are found and activated in the lymph nodes?
A
macrophages • B lymphocytes • T lymphocytes - helper T cells (CD4+) - cytotoxic T cells (CD8+) • natural killer (NK) cell
13
Q
Name the two different kinds of T lymphocytes
A
helper T cells (CD4+)
cytoxic T cells (CD8+)
14
Q
What is the first line of defense in the NON specific immune response?
A
skin and mucous membranes
15
Q
What is the second line of defense in the NON specific immune response?
A
relatively rapid response, occurs within minutes to hours, to prevent establishment of infection
16
Q
What is the second line of defense initiated by?
A
tissue injury
17
Q
What are the steps involved in the second line?
A
vasodilation
• enhances delivery of neutrophils and monocytes
- capillary leakiness
• plasma and cells able to move into interstitial spaces
- chemotaxis
• WBCs attracted to injured tissue
- phagocytosis
• relies on recognition of foreign vs. self
18
Q
How do opsonins play a role in phagocytosis?
A
opsonins are antibodies or other substances that become bound to bacteria or foreign cells
and enhance phagocytic activity
19
Q
What acts as an opsonin by enhancing phagocytic activity?
A
antibodies or complement proteins typically play this role
20
Q
What is a complement?
A
a group of proteins present at all
times in the blood, in an inactive form
21
Q
What are the 3 things that happen when complement is activated?
A
- a group of 5 of the complement proteins forms a
complex called the membrane attack complex
(MAC) which is able to insert itself in the
membrane of bacteria and create a pore or
channel that ultimately causes cell lysis and
death
2.activation of complement enhances most of the events of the normal inflammatory response - activated complement can act as an opsonizing agent, enhancing phagocytosis of
opsonized cells
22
Q
What is the membrane attack complex (MAC) related to?
A
another protein secreted by cytotoxic T cells called perforin
23
Q
most of the events of the inflammatory response are enhanced by?
A
the activation of complements
24
Q
What inhibits viral replication non-specifically?
A
release of IFN-α and IFN-β by leukocytes and fibroblasts respectively
25
what carries out the other non-specific mechanism?
NK cells that also kill non-specifically
26
What does the specific immune response defense mechanism require?
requires specific recognition of an antigen which is typically mounted against bacteria, extra-cellular viruses, and non-microbials
also called adaptive immunity and is a slower response
27
What are the two forms of specific immune response?
- cell-mediated
| - antibody mediated (humoral immune response)
28
What does antibody mediated immune response target?
it goes against bacteria and extra-cellular viruses
29
What does cell-mediated immune response target?
against intracellular viruses and cancer cells, which are ‘self cells
gone bad’, changed in some way, no longer recognized as normal ‘self’
30
What are antibodies?
proteins in the serum, also called immunoglobulins
31
What of the antibody determines the specificity to an antigen?
contain a ‘Y’ shaped variable region
32
Where are antibodies found?
on the surface of B lymphocytes, where they function as
receptors
- soluble antibodies are produced by plasma cells and circulate in
the plasma
33
Name the 5 types of antibodies
```
IgA
IgD
IgE
IgG
IgM
```
34
Components of IgA
15% of antibodies are of this type
• found in body secretions such as saliva, nasal and respiratory secretions, secreted in breast
milk
• protect against microbes that might multiply on mucous membranes
35
Components of IgD
0.2% of antibodies are of this type
• found primarily on the surface of immature B lymphocytes
• thought to be needed for maturation of B lymphocytes
36
Components of IgE
0.004% of antibodies are of this type
• found only in mammals
• present in very small amounts compared to other soluble antibodies
• capable of triggering the most powerful immune reactions
• binds to mast cells and basophils
• involved in response to parasitic infections, allergic, and hypersensitivity reactions
37
Components of IgG
```
75% of antibodies are of this type
• most abundant antibody
• this is the only immunoglobulin that can cross the placenta, providing some immunity to a
developing fetus
• activates complement
• binds to macrophages
```
38
Components of IgM
10% of antibodies are of this type
• antibody against A and B RBC antigens
• very large antibody, doesn’t diffuse into tissues easily
• potent complement activator
39
What is the most typical thing to provoke an antibody mediated response?
injury
40
Steps of the antibody mediated response?
An antigen-bearing substance enters the blood and/or
lymphatic tissue
• it is recognized by a B lymphocyte with an antibody on its surface that is specific to that antigen and the antigen binds to the antibody
• simultaneously, the antigen also encounters macrophages which phagocytize the antigen
- some of the antigen is processed by the macrophage and presented on the surface of the macrophage in a complex with the Class II MHC proteins
• the macrophage presents this antigen-MHC complex on its surface to a CD4+ (helper T) cell
- the CD4+ cell has a receptor specific forth antigen as well, but can only recognize the antigen if the phagocytic cell presents it
• the interaction of the antigen presenting cell and the helper T cell triggers the release of cytokines such as IL-1 and TNF from the macrophage which trigger the
proliferation of this specific clone of T cell
• the proliferating T cell clone signals the B lymphocytes specific to this antigen to:
- undergo mitosis and proliferate themselves
- differentiate into plasma cells
- differentiate into memory cells
41
What do plasma cells make?
soluble antibodies which are released into the plasma to free float and circulate in the blood and bind to the antigen which is the end result of this response
42
What do memory cells do?
ensure a more rapid response on
| subsequent exposure to the antigen
43
How do memory cells ensure a rapid response?
when memory cells encounter an antigen again and
are assisted by T cells, there is a rapid proliferation
into plasma cells and another population of memory
cells (peak plasma antibody concentration reached
in a few days vs 2-3 weeks.
44
Where do memory cells stay and for how long?
memory cells will stay in lymphoid tissues for months
| to years
45
What 3 things happen when a soluble antibody binds to an antigen?
1. antibody acts as an opsonizing agent to link phagocytic cells to antigen
2. activates complement via classical pathway and MAC kills cells to which antibody is attached
3. links NK cells to antigen-bearing target cells
46
What is active immunity?
```
type of antibody related immunity
• due to formation of memory cells
• developed by
- natural infection with microbe
- vaccination
can last many years and even be life-long
```
47
What is passive immunity?
type of antibody related immunity due to direct transfer of antibodies (immunoglobulins) by
- injection
- placenta (IgGs)
- breast milk (IgAs)
- protection via passive immunity is relatively short-lived, on the order of weeks
48
What immunity acts the same way each time it is exposed to a pathogen?
innate immunity which is non-specific and non-adaptive
49
What controls the cell-mediated immune response?
mediated by the CD8+ or cytotoxic
| T cell
50
Where do Tcells reside?
reside in lymphoid tissues and
respond primarily to virus-infected cells and
cancer cells
51
Process of cell-mediated immune response
infected cells will complex viral protein (antigen) with
Class I MHC and express this complex on their
surface
• specific CD8+ cells, with receptors specific to this
particular antigen/Class I MHC Complex can
recognize and bind to the infected cell
• simultaneously, antigen-presenting cells, such as
macrophages, process the antigen, complex it with Class II MHC, and present this complex on their
surface
• antigen presenting cells release IL-1, and TNF and these cytokines stimulate CD4+ cells to secrete
IL-2 and interferon gamma
• signal from CD4+ cells signals CD8+ cells to replicate
52
What do CD8+ cells secrete?
perforin and granzymes, which are part of a protein complex that gains entry into
infected or transformed cells through interaction with a particular receptor to form a vesicle within
the cell
53
What are granzymes?
proteases that activate the caspase cascade, resulting in apoptosis, killing the cell
54
Importance of CD4+
needed to promote normal humoral and cellular immune responses
- lack of CD4+ cells greatly compromises immune system function
55
What is the target of NK cells?
primarily virally infected cells
| important part of the early cell-mediated response
56
What activates NK cells?
activated in response to interferons, macrophage-derived cytokines
57
What does the adaptive response generate?
generates specific CD8+ cells to clear the infection
58
Immunodeficiency state
abnormality in the immune system that renders a person susceptible
to diseases normally prevented by an intact immune system
most are primary - inherited disorders
• B cell deficiencies
• T cell deficiencies
- very rare
• combined B and T cell deficiencies
- usually genetic
- often referred to as SCIDS - Severe Combined Immunodeficiency Syndrome
59
disorders of the complement system
- usually genetic
- result in increased susceptibility to:
• bacterial infections
• autoimmune conditions, particularly SLE
60
Disorders of phaygocytosis
usually genetic
deficiencies in ability of phagocyte to be attracted to site of infection (response to cytokines),
adhere to infected cells, phagocytize or generate enzymes/toxins to kill microbes
61
What are hypersensitivity/allergic disorders?
diseases in which immune system responses to environmental antigens (allergens) cause
inflammation and tissue damage
- typically excessive or inappropriate activation of the immune system
- the antigens themselves are usually harmless, it is the exaggerated response of the immune
system that is problematic
62
IgE mediated disorders (type I hypersensitivity)
also referred to as immediate hypersensitivity as initial
response is usually within 5 minutes
• examples include hay fever, asthma, food allergies,
anaphylaxis - all what would commonly be called allergic
reactions
• the genetic makeup of these individuals results in IgE
synthesis in response to antigenic exposure rather than
IgG.
63
What do IgE antibodies bind to?
mast cells and basophils in the blood
64
Where are mast cells found?
found in connective tissue, especially subcutaneously, in mucous membranes of
the respiratory, GI, and GU tracts, and near blood and lymphatic vessels
65
What do mast cells secrete?
histamine, bradykinin, acetylcholine, prostaglandins,
| leukotrienes, adenosine, enzymes, chemotactic factors for neutrophils and eosinophils
66
What are the physiological responses the mast cell secretions?
local vasodilation, bronchiolar
| constriction, and enhancement of all aspects of the inflammatory response
67
late phase of the allergic response
infiltration by eosinophils over hours that degranulate and the allergic response
persists as inflammation that often damages tissues
• epithelial tissue most often damaged
• occurs 2 to 8 hours after exposure, often persists for several days
68
Useful purpose of the late phase
damage parasitic larvae by attracting
| inflammatory cells to them
69
Antibody Mediated Disorders (type II hypersensitivity)
antibody binding to surface antigen results in antibody-dependent cell lysis or activation of
complement and subsequent lysis or opsonization and phagocytosis
• primary example is ABO or Rh incompatibility
- IgG or IgM antibodies react with surface antigens
70
Immune Complex Allergic Disorders (type III hypersensitivity)
soluble antibody binds to antigen forming an insoluble complex that precipitates, most often in
small blood vessels
• the complexes adhere to the vessel endothelium or are deposited in tissues
• an inflammatory response occurs at the site of deposition
examples: renal disease - glomerulonephritis, lupus
71
Cell-mediated Hypersensitivity Disorder (type IV hypersensitivity)
also called delayed hypersensivitiy or direct cell-mediated toxicity
important against intracellular pathogens such as TB or viruses
• mediated by specifically sensitized T cells
• occurs 12-72 hours after antigen exposure in a previously
sensitized (exposed) individual
• examples include contact dermatitis, Mantoux test
- Mantoux test - for TB
• uses ppd (purified protein derivative)
• injection of antigen, looking for response 48-72
hours later
72
Acquired Immunodeficiency Syndrome (AIDS)
• human immunodeficiency virus (HIV) is a retrovirus that selectively attacks CD4+ lymphocytes and
macrophages
• most transmission of HIV (75-85% worldwide) occurs via
unprotected sex
- risk also elevated in those who received transfusions
prior to 1985 and in those who inject drugs
- HIV may also be transmitted to an infant in utero, during
labor and delivery, or through breastfeeding
73
Autoimmune Disease
an inappropriate immune system activation in which the body’s own protein’s act as antigens
examples
- type 1 diabetes mellitus
- rheumatoid arthritis
- Hiashimoto’s thyroiditis, Graves disease
systemic lupus erythematosus
- myasthenia gravis
74
What is acute rejection?
rejection developing after the first 5-7 days following transplantation is
generally a result of cell-mediated immune injury
