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Immunity

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by

Hillary Bui

on 22 March 2013

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Transcript of Immunity

By Hillary Bui,
Olivia Eaton,
and Troi Graves Immunity a defense that is active immediate upon infection
same whether or not pathogen has been encountered before
exists in all plants, animals, and invertebrates
two types: barrier and internal Innate Immunity THE COMPLICATED STUFF: Innate Immunity How B-Cells and T-Cells
Are Recognized Functions of Cytotoxic
T-Cells and B-Cells Humoral Immune Response Cell- Mediated Immune Response A Host Cell must first
become infected by a
pathogen. Through phagocytosis the pathogen in enveloped. An antigen fragment is then presented on a MHC molecule. #1 #2 B-Cells recognize antigens on
pathogens by their antigen
receptors. The B-Cell then
takes in antigen fragments
and presents it on a MHC
molecule. B-Cells then wait
for helper T-Cells to activate
them. #3 Cytotoxic T-Cells recognize
infected cells by matching
their antigen receptors with
presented fragments on the
infected host cell. After
recognition, cytotoxic cells
will also present antigen
fragments on an MHC
molecule. Cytotoxic cells
will then wait for helper
T-Cells to activate them. #4 Unactivated helper T-cells
become activated by
recognizing infected host
cells. They match their
specific antigen receptors
with the presented fragments
on MHC molecules. The
host cell will emit cytokines
which will activate the helper
T-cells. Once activated the
helper T-cells will activate
B-cells and cytotoxic cells. #5 Activated Helper T-cells will
then match their antigen receptors
with antigen fragments presented
on B-cells and Cytotoxic cells.
Once B-cells and Cytoxic cells are
recognized, the Helper T-cell will
release cytokines. The cytokines
will activate B-cells and Cytoxic
cells. B-Cell Cytotoxic
Cell Activated B-cells will then
clone themselves many, many
times. Clones will become
either plasma cells or memory
B-cells. Plasma
Cells Memory
B-Cells The function of plasma cells
are to create antibodies,
which break off from the cells. The function of memory
B-Cells are to create
B-Cells that can quickly
respond to specific
antigens in the future. Antibody
Function Clones #1 Neutralization #2 Opsonization #3 Complement Pores The function of cytotoxic
cells are to kill infected
cells. They do so by making
pores in the cell and releasing
toxins that break down the
host cell's proteins. Within
the dying cell apoptosis, or
cell suicide, is initiated. THE BASICS: PATHOGENS Innate
Response Internal Barrier INVERTEBRATES only have innate immunity
Barrier: exoskeleton of an insect
Internal: chitin based barrier in intestine
Lysozymes: enzymes in intestine that break down bacteria cell walls
Hemocytes: immune cells
carry out phagocytosis
trigger production of chemicals that kill pathogens
antimicrobial peptides: secreted, short chains of amino acids that kill fungi and bacteria by disrupting their plasma membranes
only bind to molecules found on outer layers of fungi and bacteria VERTEBRATES External Barriers:
(1) Skin
sweat
commensal bacteria species
(2) Mucus
contains lysozymes
(3) Ciliated Epithelium
functions as a trap for pathogens Internal Barriers:
(1) Phagocytosis: (1) pathogen is engulfed




(2)vacuole forms around pathogen







(3) vacuole fuses with lysosome



(4) toxic compounds and enzymes destroy pathogens


(5) debris from pathogens is released by exocytosis use Toll-like receptors (TLR) to detect fungal or bacterial components of pathogens
components are missing from the organism itself, prevents self-destruction Four Main Types:
Neutrophils: circulate in blood, attracted by signals from infected tissues, engulfing pathogens
Macrophages: some migrate throughout body, others reside permanently in organs and tissues, engulfing pathogens
Dendritic cells: populate tissues that contact environment, stimulate adaptive immunity
Eosinophils: found beneath mucosal surfaces, defend against multicellular invaders (2) Natural Killer Cells: circulate through body and detect abnormal surface proteins characteristic of virus-infected and cancer cells
release chemicals that lead to cell death, inhibiting spread of virus (3) Lymphatic System: a network that distributes the lymph fluid through the body
some macropahges reside in the lymph nodes
dendritic cells reside outside of lymphatic system, migrate to lymph modes after interacting with pathogens, then stimulate adaptive immunity (4) Interferons proteins that provide innate defense by interfering with viral infections
infected body cells secrete interferons, which induce nearby cells to produce substances to inhibit the virus
some activate macrophages (5) Complement System 30 proteins in blood plasma
circulate in an inactive state and are activated by the surfaces of microbes
activation results in cascade of biochemical reactions that lead to lysis of invading cells (6) Inflammatory Response changes brought about by signaling molecules released upon injury or infection
histamine: inflammatory signaling molecule stored in granules of mast cells in connective tissues
released at sites of damage
triggers nearby blood vessels to dilate and become more permeable
cytokines: signaling molecules that enhance immune response
activated macrophages and neutrophils discharge them
promote blood flow to site of injury, causing redness and rise in temperature
blood-engorged capillaries leak fluid into tissue, causing swelling
results in pus: fluid rich in white blood cells, dead pathogens, and cell debris
minor injuries: requires local inflammatory response
large injuries: increase white blood cells, fever
septic shock: overwhelming systemic inflammatory response
low blood pressure
poor flow through capillaries Antibody mediated response
involves most cells that respond to antigens or pathogens that are in the blood and lymph
"body humors"= fluid
binding of antibodies helps to eliminate the antigens by phagocytosis and complement-mediated lysis
antigens help eliminate toxins in blood/lymph B cells produce plasma cells: the plasma cells release antibodies that bind with antigens or antigen bearing
B cells produce memory cells: provides future immunity
Macrophage & Helper T cells stimulate B cell production: antigen in engulfed by a macrophage, T cells then bind to macrophage in cell-mediated response Activated cytotoxic T cells secrete proteins to destroy infected cells
responds to any "nonself" cell, including cells invaded by pathogens
When the nonself cell binds to a T cell, the T cells undergoes a series of steps. 1) T cells produce cytotoxic cells: these destroy nonself cells
2) T cells produce helper T cells
3) Helper T cells bind to macrophages: helper T cells identify self and nonslef cells and bind to the macrophages
4) Helper T cells produce interleukins to stimulate a proliferation of T cells and B Cells: helper T cells release interleukins (b/w leukocytes/communication chemicals)
These start a pattern of positive feedback events that result in the making of interleukins, macrophages, helper T cells, B cells, and cytotoxic cells Summary of Humoral and Cell Mediated Response Both have primary and secondary responses
Primary= 1st exposure to an antigen
Secondary= acquired immunity- in the individual gets the antigen again
Memory cells of each type= helper T cells, B cell, and cytotoxic T cell
If body fluid is infected again- memory B and memory helper T cells have a secondary humoral response Why Helper T Cells are important Triggers humoral and cell-mediated responses- but doesn't carry out the responses
signals from helper T cells start production of antibodies to kill infected cells
A foreign molecule must be present to attach to antigen receptor and antigen must be presented on surface "antigen presenting cell" - activates helper T cell
B cells present antigens to activated helper T cells = B cells activated

Helper T cells stimulate cytotoxic T cells
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