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The Immune System. What are the major functions of the Immune System?. Regulation and Protection Fight disease Prevent future infections. What are the major components of the immune system?. Lymphatic System Leukocytes (White Blood Cells). What is a pathogen?. Any disease causing agent

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what are the major functions of the immune system
What are the major functions of the Immune System?
  • Regulation and Protection
  • Fight disease
  • Prevent future infections
what are the major components of the immune system
What are the major components of the immune system?
  • Lymphatic System
  • Leukocytes (White Blood Cells)
what is a pathogen
What is a pathogen?
  • Any disease causing agent
  • Ex: bacteria, viruses, parasites, toxins, fungi
what is the difference between innate and adaptive immunity
What is the difference between innate and adaptive immunity?
  • Innate immunity – target any pathogen (nonspecific); found in all organisms
  • Adaptive immunity – targets one specific pathogen (specific) – varies from individual to individual (genetics!)
what are some examples of external innate defenses 1 st line
What are some examples of external innate defenses? (1st line)
  • Skin – water-proof barrier
  • Sweat
  • Tears
  • Cilia – respiratory tract
  • Mucous membranes
  • Acids in stomach
  • Commensal microbes living

on the skin

what are some internal vertebrate innate immune defenses
What are some internal vertebrate innate immune defenses?
  • Macrophages – large phagocytic white blood cells
  • Natural Killer (NK) cells – WBCs that target cancer cells
  • Interferons – proteins produced by viral infected cells to limit spreading of viral infection
  • Complement System - ~30 different proteins that circulate in the blood and can act together with other defenses
phagocytes
Phagocytes
  • White blood cells that patrol the circulatory and lymphatic system
  • Engulf any material they do not recognize
  • Act as “Antigen Presenting Cells” following phagocytosis for possible specific response
inflammatory response 2 nd line
Inflammatory Response (2nd Line)
  • FUNCTION: to disinfect and clean injured tissues; prevent spreading of infection
  • Triggered by any damage to tissue
  • Can be localized or widespread
  • Results in Redness, Heat Production, Swelling
  • 1. Damaged cells release histamines (chemical alarm signals)
  • 2. Blood vessels dilate, blood flow to area increases, blood plasma passes out of blood vessels into interstitial fluid
  • 3. Phagocytes recruited by other complement proteins and engulf pathogens
why is the inflammatory response considered to be innate immunity
Why is the inflammatory response considered to be innate immunity?
  • The response is the same regardless of whether the invader has been previously encountered
how is the lymphatic system involved in immunity and what are the major components
How is the lymphatic System involved in immunity and what are the major components?
  • Involved in innate and adaptive immunity
  • Network of vessels, lymph nodes (packed with WBCs), and lymph (fluid)
what are the two major functions of the lymphatic system
What are the two major functions of the lymphatic system?
  • To return fluid from the interstitial spaces to the circulatory system (filtration)
  • To combat infection
how does the lymphatic system aid in combating infection
How does the lymphatic system aid in combating infection?
  • Lymph (fluid) carries microbes, parts of microbes, and toxins to the lymph nodes
  • Macrophages may engulf them
  • May trigger specific adaptive immune response
what is adaptive immunity
What is adaptive immunity?
  • “custom-tailored” defenses to each specific invader
  • Provides a strong and long lasting defense
what is an antigen
What is an antigen?
  • Any molecule that elicits an adaptive (specific) immune response
  • Ex: parts of microbes, proteins on microbes, toxins, mold, pollen
  • Foreign Molecules!
what are the two types of lymphocytes involved in adaptive immunity
What are the two types of lymphocytes involved in adaptive immunity?
  • B-lymphocytes (B cells) – humoral immune response
  • T-lymphocytes (T cells) – cell-mediated immune response
which lymphocytes are responsible for the humoral immune response
Which lymphocytes are responsible for the humoral immune response?
  • B-lymphocytes
  • Produce antibodies to fight against pathogens
  • Also produce memory cells
what is an antibody
What is an antibody?
  • “Y-shaped” protein produced by B-cells
  • Attaches to one specific antigen and helps counter its effects

**One gene can synthesize millions of

Different antibodies via alternative splicing**

finding the perfect antibody
Finding the perfect antibody…
  • Inside the lymph nodes…
  • Each B-cell is capable of producing a different antigen receptor (prior to exposure to any antigen)
  • B-cell antigen receptors “sample” antigens in the lymph nodes (does it fit?)
  • Only B-cells with reactive antigen receptors are allowed to divide (clonal selection)
  • Once the perfect match has been found, the B-cell undergoes rapid cell division, forming plasma cells, which produce and secrete 2,000 antibodies/second into the blood plasma (PROTEIN SYNTHESIS)
antibodies do not kill pathogens what do they do
Antibodies do not kill pathogens, what do they do?
  • Neutralization: bind to surface proteins preventing ability to infect; easily recognized by macrophages
antibodies do not kill pathogens what do they do1
Antibodies do not kill pathogens, what do they do?
  • Agglutination: (clumping together); antibodies bind to the antigen on multiple cells; easy for macrophages to identify
antibodies do not kill pathogens what do they do2
Antibodies do not kill pathogens, what do they do?
  • Precipitation: antibodies link dissolved antigen molecules together causing them to solidify; recognized by macrophages
antibodies do not kill pathogens what do they do3
Antibodies do not kill pathogens, what do they do?
  • Activation of complement system: Complement proteins attach to foreign cell, and act together to poke holes in the membrane, causing the cell to rupture
how does the production of memory cells help promote long lasting immunity
How does the production of memory cells help promote long lasting immunity?
  • B-lymphocytes (and some T-lymphocytes) produce memory cells which last for a very long time in the lymph nodes
  • Activated by a second exposure to the antigen to produce the antibodies to fight it
  • Stronger and faster response
what is the purpose of a vaccine how are vaccines produced
What is the purpose of a vaccine? How are vaccines produced?
  • To prevent infection from a specific pathogen by introducing the antigens of the pathogen to the immune system
  • Two types of vaccines:
    • Live-attenuated viruses (weakened)
    • Dead viruses
what happens in your body when you receive a vaccination
What happens in your body when you receive a vaccination?
  • Humoral immune response is triggered
  • Production of antibodies and memory cells
  • **Why is it that vaccines do NOT always provide life-long lasting immunity?**
  • Mutations in the pathogens DNA changes their antigens, making the produced antibodies ineffective
what is the difference between active and passive immunity
What is the difference between active and passive immunity?
  • Passive Immunity: receiving premade antibodies; short lasting
    • Ex: breastmilk, antibody injection; antivenom
  • Active Immunity: the person’s own immune system actively produces antibodies; long lasting
    • Ex: vaccine, natural exposure to a pathogen
what types of cells are involved in the cell mediated immune response
What types of cells are involved in the cell-mediated immune response?
  • Antigen-Presenting Cells (Macrophages/Phagocytes)
  • T-helper Cells
  • Cytotoxic T Cell (Killer T cells)
what is the role of antigen presenting cells in the cell mediated immune response
What is the role of antigen-presenting cells in the cell-mediated immune response?
  • After ingesting a pathogen, APCs display antigens on their cell membrane
  • “Major Histocompatibility Complex” = self protein and foreign antigen
  • Expressed in all phagocytes, infected cells, and many cancer cells
how do apcs activate t helper cells what do the t helper cells do following activation1
How do APCs activate T-helper cells? What do the T-helper cells do following activation?
  • T-helper cells interact with the “Major Histocompatibility Complex” on the APC (receptor recognition)
  • T-helper cells will then activate specific B cells and T cells
how do cytotoxic t cells destroy infected cells
How do cytotoxic T cells destroy infected cells?
  • Following recognition and bindingto the MHC/antigen complex on infected cells, T-cells will “shoot” a perforin complex into the membrane of cells which triggers cell death via lysis or apoptosis
what about allergies
What about Allergies?
  • Immune response to non-pathogenic foreign molecules (allergens)
  • Inflammatory response activated (often in the respiratory system) due to release of histamine
  • Treatment: antihistamines, epinephrine
what is an autoimmune disease
What is an autoimmune disease?
  • Immune response to populations of body cells
  • Treatments: immunosuppressant drugs; alleviation of specific symptoms
  • Ex: Type 1 diabetes mellitus: cytotoxic T cells attack insulin producing cells
  • Ex: MS: T cells react against myelin sheath
  • Ex: Rheumatoid arthirtis: antibodies target cartilage and bone cells at joints
hiv aids
HIV/AIDS
  • HIV destroys helper T cells – uses the cells as virus producing factories (~1,000 per day) and eventually killing the cell
  • Greatly impairs the humoral and cell-mediated immune defenses
  • AIDS patients are more susceptible to cancers and opportunistic infections
  • Rapid evolution of HIV complicates treatment
prokaryotes immune systems
Prokaryotes Immune Systems
  • Restriction Enzymes!
  • Cut up foreign DNA (of a bacteriophage) at specific restriction site sequences
  • Protect their own DNA by adding methyl groups to the same restriction sites (preventing cutting)
  • Bacteriophages have evolved mechanisms to evade this defense
prokaryotic immunity
Prokaryotic Immunity
  • A: Restriction Enzyme is successful
  • B: Evolved mechanisms in bacteriophages to evade degradation
fungi and plants immunity
Fungi and Plants Immunity
  • Rely on the production of a wide variety of chemicals that can cause unpleasant effects in would-be pathogens and predators
fungi death cap mushroom
Fungi – Death Cap Mushroom
  • If consumed, can cause irreversible liver failure in humans
fungi penicilium genus
Fungi – Penicilium genus
  • Produce antibiotics (like penicillin) to protect against bacterial infections
plants defenses against pathogens
Plants – Defenses against Pathogens
  • First line of defense – physical barrier of epidermal cells
  • If that fails, plant cells are damaged by infection…
  • In response, plants…
    • Seal off the infected areas
    • Release microbe-killing chemicals to signal local cells to do the same -> infected and local cells induce cell death
    • Plant hormones also secreted to prevent systemic spreading of the pathogen to other parts of the plant AND to stimulate production of defense chemicals
figure 33 13b s6

Figure 33.13B_s6

5

3

Signal

transduction

pathway

Enhanced

local

response

1

Binding of the

pathogen’s Avr

protein to the

plant’s R protein

R protein

6

Additional

defensive

chemicals

4

Avirulent

pathogen

2

Hormones

Signal

transduction

pathway

Avr protein

Recognition between R and Avr proteins,

leading to a strong local response

Systemic acquired

resistance

plant defenses against herbivores
Plant defenses against herbivores
  • Herbivores are animals that mainly eat plants.
  • Plants use chemicals to defend themselves against herbivores and pathogens.
  • Plants counter herbivores with
    • physical defenses, such as thorns, and
    • chemical defenses, such as distasteful or toxic compounds.
figure 33 13a s5

Figure 33.13A_s5

Plant defense against herbivores

4

5

Wasp is attracted

The

wasp

lays

eggs

3

Synthesis

and release

of chemical

attractants

Plant cell

1

Damage to plant

and chemical in

caterpillar saliva

2

Signal

transduction

pathway

animals invertebrates insects
Animals – Invertebrates - Insects
  • Innate Immunity Only (LACK adaptive immunity)
  • Examples of Physical Barriers:
    • Exoskeleton
    • Low pH
    • Lysozyme enzyme secretion to break down bacterial cell walls
  • Immune cells capable of phagocytosis
  • Production of antimicrobial proteins to help destroy invaders