Lecture 1 Flashcards
(113 cards)
1
Q
Microbes result in what type of diseases?
A
Infectious diseases
2
Q
How do extracellular microbes survive in animals?
A
By growing extracellularly and being immersed in nutrients
3
Q
Where in the body do extracellular microbes grow?
A
In any part of the body
4
Q
How do intracellular microbes survive and where does this occur?
A
They invade, live, and replicate intracellularly
Occurs within animal cells
Uses host- cell energy resources
5
Q
What is an example of an intracellular microbe and broadly how does it work?
A
Viruses
Hide and multiply in host cell
6
Q
What is one way to get rid of intracellular microbes?
A
Using antibiotics
These microbes tend to develop resistance which makes them hard to treat
7
Q
There is a constant battle between invading microbes and _____ _____.
A
Immune system
8
Q
Microbes are _____ in nature.
A
Waterborne.
9
Q
Define Immunity
A
A set of cooperative defense mechanisms which provide protection from various infectious diseases
10
Q
Define Immunopathology
A
Non-specific immune response against microbes that causes tissue injury
Also known as collateral damage
Can be the result of non-specific immune response
11
Q
What is the response in the tissues after collateral damage occurs?
A
Tissue remodeling
12
Q
Define Antigens
A
Non-infectious foreign substances that can elicit an immune response
Anything that is presented to the body that interacts with antibodies
Substances that induce an immune response
Anything that is presented to the body that at least generates antibodies
NOT involved with pathogen or bacteria
13
Q
Self- antigens in the body can elicit what kind of response?
A
Autoimmune response
Critical for cells to be able to differentiate between self and non-self
14
Q
T/F: Each microbe has many microbial antigens
A
True
15
Q
Define Antibody
A
Protein produced by immune system when it detects antigens
16
Q
Antigen- Antibody binding can be compared to what?
A
Lock and key
17
Q
Define Epitope
A
Antigenic determinant
Portion of antigen molecule to which an antibody binds
18
Q
The smallest epitope possible onto which an antibody can bind is how many amino acids? Sugar residues?
A
3 - 6 amino acids
5 - 6 sugar residues
- can occur on unfolded (denatured) portion or folded protein
19
Q
T/F: Antigen can NOT contain several different epitopes to which individual responses are made
A
False
20
Q
Antibodies bind to _____ antigenic epitopes which is dependent on what property of the molecule?
A
Conformational
Dependent on folding of the molecule
21
Q
What kind of amino acid sequences do T cell receptors recognize?
A
Linear amino acid sequences
22
Q
Haptens are _____ that _____.
A
Very small antigens
Can bind to antibodies but cannot initiate an immune response
- do not have enough structural information to generate an immune response
23
Q
Define Immunogens
A
Antigens that can stimulate an immune response
24
Q
Relate Immunogens to Antigens
A
All immunogens are antigens but not all antigens are immunogens
25
How do antigens travel via fixed elements?
Plasma delivers antigens to tissues
Leaks into lymph nodes via capillaries and goes into secondary lymphoid organs
26
Characteristics of Mucosal Immune Tissue
Secondary lymphoid organ
Largest immune organ in body
Located at places with thin epithelial layers and at interface of environment and body
27
Characteristics of Innate Immunity
First line of defense against infection
Pre-existing
Works rapidly - response will be same every time for common/ similar things
Gives rise to acute inflammation
Has some specificity for antigens
Has no memory
28
In order for the innate immune system to have specificity for antigens, what feature must the antigen have?
Must be a common antigen
29
Why doesn't the innate immune system have memory?
Due to lack of antigen specificity and recognition
30
Antimicrobial peptides target _____
Pathogenic microorganisms
Works due to osmotic lysis
31
Define Complement. How is it related to the surface of the pathogen?
System of plasma proteins that enhances the ability of antibodies and phagocytic cells to clear pathogens from an organism
Activated and creates membrane attack completes on surface of pathogen
32
What occurs in Acute Phase Proteins in response to tissue injury, acute infections, burns, or inflammation?
Change in their plasma concentrations
[] increases when have one of those responses
33
Define Cytokines
Cell signaling molecules that aid cell to cell communication in immune responses
Originate from innate immune cells
Work with macrophages
34
How do cytokines work?
Via messaging that produces small proteins
Cells have receptors that messages bind to
35
Define Chemokines
Subfamily of cytokines secreted by immune cells to induce chemotaxis in nearby cells
36
What is different in Adaptive immunity compared to innate immunity?
Takes longer to develop
Is highly specific
Shows memory
37
T/F: generation of specific receptors is a feature of adaptive immunity
True
38
What is adaptive immunity controlled by?
Signals generated by immune cells involved in innate immune response
39
What are the two functions of cytokines?
Regulate growth and differentiation of all immune cells
Activate the effector functions of lymphocytes and phagocytes
Cytokines have high affinity responses
40
Cytokines act via specific _____ _____ expressed on _____ _____.
Signaling receptor ; target cells
41
What is the major response in the GI system related to adaptive immunity?
Cellular and chemical barriers
- lymphocytes in epithelia
- antibodies secreted at epithelial surfaces
42
Characteristics of early Innate Immune responses
Exists before infection
Poised to respond rapidly to infection
- provides 1st assessment of pathogen
Depends on if pathogen is extracellular or intracellular **
Responds in same way to repeated exposures to antigen
Recognizes common antigens belonging to groups of related microbes
Does NOT distinguish fine differences between microbes
43
Primary function of Phagocytes
Ingest and destroy microbes and get rid of damages tissues
"clean up" cell
44
What are the steps in the functional responses of phagocytes?
1. Recruitment of the cells to the sites of infection
2. Recognition of and activation by microbes
3. Ingestion of the microbes by the process of phagocytosis
4. Destruction of ingested microbes
- occurs via fusion with lysosomes
45
Which cell is one of the mediators of the earliest phases of the inflammatory reactions?
Neutrophils
React before any other cells come into tissue
Stored in bone marrow
- Released quickly after signaled by cytokine (granulocyte colony- stimulating factor) and activates phagocytosis
Not produced de nuovo
46
What is a common feature between Mast cells, Basophils, and Eosinophils?
Cytoplasmic granules
| - filled with various inflammatory and antimicrobial mediators
47
Where are mast cells found?
Sites in body that are exposed to external environment
Found in close proximity to blood vessels at these locations
48
What advantage do Mast cells have by being located near capillaries?
Allows them to regulate vascular permeability and effector- cell recruitment
49
Which cell functions as the breeching between innate and adaptive system?
Dendritic cells
50
Describe the path from monocyte to macrophage
Mature monocytes enter into blood circulation > Migrate into tissues where they further mature into macrophages
Occurs especially during inflammation
51
Are tissue resident macrophages specific in any way?
Yes: have tissue specific and niche specific functions
52
Where are antigens made and where are they found?
Antigens are made in primary lymphoid organs and are found in secondary lymphoid organs
53
Describe the mechanism of chemokines
1. Chemokines are sensed by cells
| 2. Cells move into tissues by following gradient created by chemokines
54
What do chemokines regulate?
Cell migration and movement
55
How will the immune system fight a GI infection with enteric bacteria?
Self cannot send immune cells bec there is no oxygen here
Immunogens produce a specific class of antibodies which are secreted at the infection site and are absorbed on the surface of the bacteria and cannot enter the enteric epithelium
56
Where are most of the innate immune cells located and when are they released?
Most are stationed in the blood and are delivered to tissues on demand as a part of the inflammatory response/ inflammation
57
T/F: Most interactions with pathogens are resolved at the local level and don't ever encounter adaptive immunity.
True
58
Activated phagocytes secrete _____ to promote or regulate immune responses?
Cytokines
59
Examples of phagocytes
Neutrophils
| Macrophages
60
Describe the pathway of Neutrophils from storage to action
Stored in bone marrow > released quickly after signal from cytokine > phagocytosis > quickly move into tissue
61
After entering the tissues, how long do neutrophils function for and how do they act?
Only function for 1 - 2 days before dying
Throw DNA out of cell > take in stuff/ phagocytosis > digest > die
62
Functions of Tissue- Resident Macrophages
1. Dedicated homeostatic functions
- clearance of cellular debris and iron processing
2. Tissue immune surveillance
3. Response to infection
4. Resolution of inflammation
Function depends on the tissue into which they are allocated
63
What kind of cells are Dendritic cells and how do they act?
Antigen Presenting cells (APCs)
Have long surface membrane extensions (dendrites) - take antigens from site of infection and bring it to lymph nodes
64
How are dendritic cells related to adaptive immunity?
Are potent stimulators of T cells which can induce the adaptive immunity
65
How do mast cells, basophils, and eosinophils (generally) work?
Are designed to work against multicellular pathogens
Protect against helminths and reactions that cause allergic diseases
Tissue remodeling creates collagen pockets that are contained in the tissues
66
What is the immediate response to mast cell activation?
Immediately release granules filled with histamine > results in dilation
67
How do mast cells modulate the behavior of cells?
Release mediators (cytokines)
Do not have direct cell-to-cell contacts
68
The innate immune system is considered what stage of the immune response and what occurs during this stage?
Decision- making stage
Evaluates the invader in the context of intracellular vs extracellular microbes.
- based on this, it provides instructions to adaptive immunity
69
Why is phagocytosis mediated by neutrophils?
Neutrophils increase by 300% after infection whereas monocytes increase relative to blood cells in circulation
70
How does the immune system compensate for not being able to have a ton of B and T cells circulating?
Generated specific receptors
B and T cells (as a group) recognize the same epitopes but 2 different individual B cells/ T cells have different receptors and different epitopes
71
Describe receptors in adaptive immunity (general)
Receptors are specifically tailored to antigens on surface of pathogen
Recognize very minute changes
Provide extremely specific type of recognition
- based on specific receptor on surface
72
Compare specificity between innate and adaptive immunity
I: specific for antigens shared by groups of related microbes and molecules produced by damaged host cells.
- targets common antigens
A: for microbial and nonmicroblal agents
73
Compare diversity between innate and adaptive immunity
I: limited
A: very large diversity
74
Compare memory between innate and adaptive immunity
I: none
A: yes
75
Compare reactivity to self between innate and adaptive immunity
I: none
A: none
76
Describe receptors in adaptive immunity
Receptors are specifically tailored to antigens on surface of pathogen
Extremely specific type of recognition based on specific receptor on surface
Recognize very minute changes
77
What can T cells recognize?
Proteins only
Recognizes proteins and proteins processed and presented to them by another cell (APC) as small peptides of surface
78
What can B cells recognize?
Can recognize anything
79
What types of interactions are critical for development of specific immunity?
Interactions between T cells and B cells
Interactions between T cells and antigen presenting cells
80
What is the 2- step recognition for adaptive immunity?
1. Intracellular vs extracellular microbes
- I = T cells
- E = B cells
2. Cell mediated vs humoral
- CM = T cells = I
- H = B cells = E
81
Define Humoral Adaptive Immunity
Immunity that involves the production of soluble molecules (immunoglobulins)
Involves extracellular microbes
The principal defense mechanism against extracellular microbes and their toxins
- secreted antibodies can bind to these microbes and toxins and assist in their elimination
82
Describe Humoral Adaptive Immunity development and mediation
Based on the development and maturation of B cells in the bone marrow
Mediated by antibodies in the blood and mucosal secretions by B cells
83
Describe the mechanism of antibodies in Humoral Adaptive Immunity
1. Antibodies recognize microbial antigens and bind with high affinity
2. After binding, they neutralize the infectivity of the microbes
- interacts with catalytic center and prevents activity of the enzyme
3. Target microbes for elimination by various effector mechanisms
- phagocytes: have high affinity receptors on surface which recognize part of antibody that is not interacting with antigen
84
What is the general course of action during Humoral Adaptive Immunity?
B cells secrete antibodies that prevent infections and eliminate extracellular microbes
85
Who is Paul Ehrlich and what discovery did he make?
Father of Humoral Immunity
Found that immune cells can secrete specific receptors which recognize microbial toxins and combat invading microbes
- model for the function of B cells in humoral immunity
86
How is cell- mediated Immunity controlled?
Controlled by responses of T cells
| - function in concert with antigen- presenting cells and phagocytes to eliminate microbes
87
What does cell- mediated immunity mediate?
Mediates host defense against intracellular microbes (viruses and bacteria) where they are inaccessible to circulating antibodies
88
Cell- mediated immunity is based on what and how is a response generated?
Based on development and maturation of T cells in thymus
Response is generated when mature T cell is stimulated by an antigen
89
What is the function of cell- mediated immunity?
Killing infected host cells to eliminate reservoirs of infection
Have very fine tuned mechanism so only touch damaged cells
- allows it to distinguish between infected and non-infected cells
90
What is the general course of action during cell- mediated immunity?
T helper cells activate tissue-specific macrophages to kill phagocytize microbes, or cytotoxic T cells to directly destroy infected cells
CTL takes antigens and puts them on surface in order to be tagged and killed by T cells
91
Who is Elie Metchnikoff and what did he discover?
Father of cell- mediated immunity
Discovered special immune cells and called them phagocytes
Unable to prove that specific immunity to microbes could be mediated by cells
92
Describe the phases of the adaptive immune responses
Antigen recognition
- B cells can interact with any antigen without any assistance
Lymphocyte activation
- sick for 5-7 days as we develop a response
- clonal expansion and differentiation
- here we have reached optimal levels
Antigen elimination
Contraction (homeostasis)
- reduction in number of cells
- everything that is activated here will produce memory cells
Memory
- surviving memory cells engage with anti-apoptotic properties
93
Describe specificity of adaptive immunity
Ensures that immune response to a microbe is selective to that microbe
94
Describe diversity of adaptive immunity
Enables the immune system to respond to a large variety of antigens
95
Describe memory of adaptive immunity
Increases the ability to combat repeat infections by the same microbe
Protects us in the long term from repeated exposures
Incredible resistance to apoptosis
96
Describe clonal expansion of adaptive immunity
Increases the number of antigen- specific lymphocytes to keep pace with microbes
97
Describe specialization of adaptive immunity
Generates responses that are optimal for defense against different types of microbes (not self)
98
Describe contraction and homeostasis of adaptive immunity
Allows the immune system to recover from 1 response so that it can effectively respond to newly encountered antigens
Contraction of immune response = decreasing number of cells
99
Describe non-reactivity to self of adaptive immunity
Prevents injury to the host during responses to foreign antigens
100
What question does the clonal selection hypothesis ask?
How does the immune system respond to a large number of different antigens?
101
Describe the clonal selection hypothesis
Antigen- specific clones of lymphocytes develop before and independent of exposure to antigens
- Clones have identical receptors on their surfaces
- clone is generated without ever seeing antigen**
102
What is the benefit of immune system generating a very large number of clones during the maturation of lymphocytes?
It maximizes the potential for recognizing diverse microbes
103
Describe the pathway of the clonal selection hypothesis
1. Antigen introduced into individual
2. Lymphocytes with receptors for this antigen seek out and bind antigens
3. Lymphocytes are triggered to proliferate and differentiate giving rise to clones of cells specific for the antigen
4. Cells from the clones react with the antigen to neutralize or eliminate the antigen
5. Some antigen- specific cells late in the immune response are responsible for the memory involved in adaptive immunity
104
Lymphocyte clones mature in ___ ___ ___ in the ___ of antigens. ___ of ___ ___ specific for diverse antigens enter lymphoid tissues. ___ ___ ___ are activated by antigens which act to ___ antigen. What type of responses occur?
Generative lymphoid organs; Absence
Clones; mature lymphocytes
Antigen- specific clones; neutralize
Antigen- specific immune responses occur
105
Compare memory cells and naive cells in terms of effectiveness, number, speed of response
Memory cells are more effective in combating microbes
Memory cells are more numerous than naive cells specific for the antigen
Memory cells respond faster and more effectively
106
What is an important goal of vaccinations?
Generation of memory responses
107
What happens to antibody levels and memory cell numbers after each immunization?
Antibody levels decline with time after each immunization
= contraction of immune response
Number of memory cells increases
108
Define active immunity
Conferred by a host response to a microbe or microbial antigen
Response is specific and has memory
Provides resistance to infection and is specific for microbial antigens
109
Define passive immunity
Conferred by adoptive transfer of antibodies or T cells specific for the microbe
- acts via neutralization
Response is specific but does not have memory
Provides resistance to infection and is specific for microbial antigens
110
Describe B lymphocytes
Recognize soluble antigens
Develop into antibody secreting cells
Protect against extracellular microbes
Functions: neutralization of microbe, phagocytosis, and complement activation
111
Describe T helper lymphocytes
Recognize antigens on surfaces of antigen- presenting cells
Secrete cytokines which stimulate different mechanisms of immunity and inflammation
Help produce cytotoxic T cells
Activate macrophages
Proliferation and differentiation of T and B lymphocytes
Part of inflammatory response
112
Describe cytotoxic T lymphocytes
Recognize antigens on infected cells and kill them
Triggers apoptosis
113
Describe regulatory T cells
Suppress and prevent immune responses
Help to prevent unwanted reactions
Suppress other lymphocytes
