Ch 43 pt 1 Flashcards
What are pathogens?
agents that cause disease
dedicated cells of the _________ interact with and destroy ________
Immune system, pathogens
Name the 4 cellular pathogens
1) parasites
2) protozoa
3) fungi
4) prokaryote
Name the 2 acellular pathogens
1) virus
2) prions
What are the 2 types of molecular recognition that allow detection of non-self molecules, particles, and cells?
1) Innate Immunity
2) Adaptive Immunity
What is innate immunity? (2)
1) recognition of traits SHARED by broad ranges of pathogens using a SMALL set of receptors
2) Rapid response
What is adaptive immunity? (2)
1) recognition of traits SPECIFIC to particular pathogens using a VAST array of receptors
2) Slower response
What are the 2 types of defenses in innate immunity?
1) Barrier defenses
2) Internal defenses
What are the 3 barrier defenses?
1) skin
2) mucous membrane
3) secretions
What are the 4 types of internal defenses
1) phagocytic cells
2) natural killer cells
3) antimicrobial proteins
4) inflammatory response
PAIN
What are the 2 types of adaptive immunity responses? (describe them)
1) humoral response: ANTIBODIES defend against infections in body FLUIDS
2) cell-mediated response: CYTOTOXIC CELLS defend against infections in body CELLS
What are the 3 parts of innate immunity in invertebrates?
1) An exoskeleton made of chitin forms 1st barrier
2) chitin based barrier + lysozyme protect digestive system
3) hemocytes in hemolymph carry out phagocytosis
What does lysozyme do?
Breaks down bacterial cell walls
What do hemocytes do?
Secret antimicrobial peptides that disrupt plasma membrane of fungi and bacteria
How does the immune system recognize bacteria and fungi?
Structures on their cell walls (antigens)
How do insects defend against viruses?
they can recognize virus double-stranded RNA
Explain antiviral defense in insects (3)
1) virus infects host cell and begins replicating ssRNA
2) Dicer-2 recognizes foreign dsRNA and cuts it up
3) Argo protein picks one up and now “knows” what to destroy by cleaving
What is the main goal of innate immunity in vertebrates?
recognize that something is foreign
What are the barrier defenses in innate immunity in vertebrates?
In respiratory, urinary, and reproductive tracts:
1) Skin
2) Mucous membrane
What allow for the removal of microbes?
mucus traps
What bodily fluids are hostile to microbes?
1) Saliva
2) Mucus
3) Tears
by lysozymes that break cell walls
What are the affects of low pH of the skin and digestive system?
prevents growth of bacteria
How do mammals detect invading pathogens?
use cells called Toll-like receptors (TLR’s)
How do TLR’s recognize pathogens?
they recognize fragments of molecules of a set of pathogens
What are the 2 main types of phagocytic cells in mammals?
1) neutrophils
2) macrophages
What do neutrophils do and where are they found?
1) they respond to signals from damaged tissue or presence of pathogens
2) found circulating in blood
Where are macrophages found? (2)
1) found migrating through body
2) permanently in organs/tissues
What are the 2 additional types of phagocytic cells?
1) dendritic cells
2) eosinophils
What do dendritic cells do?
Stimulate development of adaptive immunity
Where are dendritic cells found? (2)
1) They are found in tissues in contact with the environment
2) They migrate to lymph nodes after pathogen detection
What do eosinophils do?
they discharge destructive enzymes against parasites (multicellular invaders)
What are the functions of Natural Killer cells? (2)
1) detect abnormal cells
2) They release chemicals leading to cell death
Where are natural killer cells found?
They are found circulating the body and involve the lymph system
What is the main function of antimicrobial peptides and proteins? (2)
1) They attack pathogens
2) impede their reproduction
What are the characteristics of interferon proteins? (3)
1) interfere with viruses
2) activate macrophages
3) released by cells to warn neighboring cells
Where are complement proteins made?
They are produced in your liver
Complement proteins circulate in their _______ form. Why?
inactive; so they don’t attack the body
What activates complement proteins?
pathogen contact, which stimulates cascade of activation
What are the 3 affects of complement proteins?
1) Opsonization
2) Forms membrane attack complex
3) Enhance inflammation
What is opsonization?
Where complement proteins coat the surface of a pathogen which allows phagocytes to engulf them easily because of specialized receptors
What is a membrane attack complex?
Where complement proteins make a hole in pathogen membrane which leads to lysis
An inflammatory repsonse can be _______ or _______
local; systemic
What is inflammation?
Pain and swelling from molecules released by injury or infection
What are mast cells?
Immune cells that release histamine
Where are mast cells located?
In connective tissue
What does histamine do? (2)
1) triggers vasodilation
2) increases the permeability of blood vessels
What is the role of activated complement cells in the inflammatory response? (2)
1) promote the release of histamine
2) attract more phagocytic cells
How does vasodilation help an inflammatory reponse?
It helps deliver antimicrobial proteins
What is pus?
Pus is a fluid rich in white blood cells, dead pathogens, and cell debris
What is a fever?
It is a systemic inflammatory response
What is a fever triggered by?
It is triggered by substances released by macrophages in response to certain pathogens
Characteristics of septic shock (2)
1) life-threatening
2) caused by an overwhelming inflammatory response
What are the 2 examples of pathogens that evade the innate immune system?
1) Streptococcus pneumoniae
2) Tuberculosis (TB)
What does adaptive response rely on?
Two types of lymphocytes
1) B cells
2) T cells
Where do T cells mature?
They mature in the thymus above the heart
Where do B cells mature?
They mature in bone marrow
What are antigens?
Substances that can elicit a response from a B or T cell
What are Antigen Receptors? (2)
1) Proteins that are specific to part of one molecule of a pathogen
2) how T or B cells bind to antigens
What is an epitope?
Accessible part of an antigen that binds to an antigen receptor
B or T cells are specialized to ________ on a _________
Recognize epitope; specific antigen
B cell antigen receptor traits
Y shaped molecule with two identical heavy chains and two identical light chains with disulfide bridges
Describe C and V regions on B cells
C regions vary little while
V regions differ greatly
What do the variable regions provide?
Antigen specificity
When are B cells activated?
When the Paratope on the V regions of the antigen receptor binds to the epitope on the antigen
What happens when B cells are activated
They secrete a soluble form of the protein called an antibody or immunoglobulin (lg)
What is the difference between antibodies and cell antigen receptors
Antibodies are secreted (not membrane bound)
A T cells receptor consists of
two different polypeptide chains (alpha and beta)
T cell antigen receptor regions:
Tips of the chains form V region
Rest is C region
What do T cells do
Bind to epitope of antigen fragments displayed or presented on a host cell
Antigen fragments are presented by
cell-surface proteins called major histocompatibility complex (MHC) molecules
What are MHC molecules?
Host proteins that display the antigen fragments on the cell surface
What is Antigen presentation?
When MHC molecules bind and transport antigen fragments to the infected cell’s surface
What can the T cell bind to
Both the antigen fragment and MHC molecule
What are the four major characteristics of the adaptive immune system?
1) Immense diversity of lymphocytes and receptors
2) Self-tolerance: lack of reactivity against an animal’s own molecules and cells
3) B and T cells proliferate after activation
4) Immunological memory
What does the immune system do by combining variable elements?
It assembles millions of different antigen receptors from a small number of parts
What is immunoglobulin (Ig) gene enconde?
The light chain of the B cell receptor
What parts of the gene can produce many different chains?
V, J, and C regions
What does the recombinase enzyme do?
Acts randomly to connect different V and J segments of the Ig gene in each B cell
Rearrangements traits
1) Permanent
2) Passed on to daughter cells with lymphocyte division
What happens to the rearranged genes
They are transcribed and translated to produce unique antigen receptors
Lymphocytes mature in
1) Bone marrow
2) Thymus
- Where they are tested for self-reactivity
If lymphocytes don’t pass the “test”
apoptosis
There are ________ lymphocytes with antigen receptors for any _______
few; epitope
What happens in lymph nodes regarding antigens?
An antigen is exposed to a steady stream of lymphocytes until a match is made
What does the binding of a mature lymphocyte to antigen initiate?
Events that activate the lymphocyte
Activated lymphocytes undergo
Clonal Selection
What is clonal selection?
process of creating clones
What are the clones of activated lymphocytes called?
effector cells
What do effector cells do?
they act immediately against the antigen
Effector cells that secrete antibodies are called
Plasma Cells
What are memory cells?
Some long lived cells that give rise to effector cells if the same antigen is encountered again
What is immunological memory responsible for?
Long-term protection against diseases
What does the first exposure to specific antigen represent
The primary immune response:
clone of lymphocytes
What happens in the secondary immune response?
memory cells facilitate a faster, more efficient response from a reservoir of T and B memory cells
What happens in the humoral immune response?
Antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph through B cells, plasma cells
What happens in the cell-mediated immune response?
Specialized T cells destroy affect host cell
What do helper T cell (effector cells) activate? (2)
1) Humoral immunity
2) Cell-mediated immunity
Where must the antigen be displayed on?
The surface of an antigen-presenting cell which allows the bind of the antigen to the receptor on the helper T cell
What are the 2 types of Antigen Presenting proteins?
1) Class I MHC
2) Class II MHC
What does Class 2 MHC do?
Provide molecular signature by which antigen presenting cells are recognized
What happens when helper T cells bind to antigen and the class 2 MHC molecule
Cytokine signals are exchanged between two cells:
interleukin 1 and interleukin 2
What kind of signals are cytokine signals?
apocrine
What happens when the helper T cell is activated
Forms a clone of helper T cells, which then activate the appropriate B cells
What type of cells have class I MHC?
all body cells
Which cells have Class II MHC?
1) dendritic cells
2) macrophages
3) B cells
What is CD4?
a glycoprotein that verifies whether an antigen is really foreign
Where is interleukin 1 released and what does it do?
it is released from the dendritic cell
it proliferates the helper T cells
Where is interleukin 2 released and what does it do?
it does 3 things
It is released from the helper T cells
1) it proliferates helper T cells
2) it activates B cells (release antibodies)
3) it activates cytotoxic T cells to become killer cells
