Z333 Lecture

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Lecture 13 Ch. 43 Immune System

• I. Overview
• Innate Immunity
• A. components
• B. cells
• IIII. Adaptive/acquired immunity
• A. Lymphocytes
• i. B-cells
• ii. T-cells
• B. humoral vs. cell-mediated immunity
• C. Antibodies
• D. MHC molecules
• IV. Immune memory
• V. Immune System Problems
• VI. Preparation for next lecture

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Thought Question
Why do we not get sick EVERY time someone near us
sneezes?
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Overview
Irritants Pollen Dust
Pathogens Viruses Bacteria Macroparasites
For example
Virus Bacteria Macroparasites
Influenza Strep Malaria
Ebola Black Plague Sleeping Sickness
Chicken Pox Salmonella River Blindness
West Nile Virus E. Coli Elephantiasis
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Overview
A Way In?
Skin breeches (cuts, punctures, scrapes)
Mucus membranes Eyes Nose Mouth Vagina Urethra
Antigens foreign molecules specific to the
invader
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Immunity Overview
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External Barriers
Innate Immunity

• Skin
• Dry dead cells
• Constantly sloughed off
• Secretions
• Contain natural antibiotics
• Mucus physically traps microbes

Internal Barriers
Phagocytic cells detect and engulf
pathogens Mast cells cause inflammation and
alert of damaged tissues
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Innate Immunity
Leukocytes
Phagocytes - ingest foreign particles cellular
debris Macrophages consume many
cells Neutrophils die upon consumption Dendritic
cells stimulate adaptive immunity Eosinophils
helpful against parasites, destructive enzymes
Dendritic cell
Natural killer cells Attack cancerous or infected
body cells Use proteins enzymes to lyse cells
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Inflammation
Innate Immunity

• Initiated by damaged or infected cells
• Histamine release by mast cells
• Capillary flow and permeability increased
• Phagocytes drawn to area

Cytokines recruit more lymphocytes ? leads to
pus, swelling, redness, heat
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Inflammatory Symptoms
Innate Immunity

• Warm, red, painful
• Result of leaky capillaries
• Increased fluid secretions
• Removal of dead cells and waste
• Pain
• Swelling, chemical response
• Alerts injured organism

NSAIDs
Leukocytes and fluid pus
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Innate Immunity
Antimicrobial peptides first discovered in
insects (like Drosophila). Here, AMPs engineered
to glow green upper fly infected by bacteria.
Antimicrobial peptides in vertebrates the
complement family of proteins, activated by
infection and lyse infected cells Interferons
chemicals made by infected cells, trigger
anti-viral response
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Adaptive Immune System
Acquired/ adaptive immunity lymphocytes made in
bone marrow ? B cells and T cells
mature in bone marrow Antibodies secreted or
embedded in B cell membrane
mature in thymus Cozy up to infected cells, bind,
sometimes lyse
Responsible for circulating antibodies,
remembering pathogens, destroying infected cells
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B cells
Adaptive Immune System

• Humoral immunity
• B cells antibodies attack pathogens before they
  enter cells
• After encounter pathogen, B cells differentiate
  into memory B cells and antibody-producing cells

Each B cell produces unique antibodies Over 100
million different antibodies in body ? chances
of an antigen encountering one that fits are
high
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Antibody action
Adaptive Immune System

• Defend against pathogens in blood or fluid
• Can inactivate pathogens by binding to epitopes
• Can stimulate phagocytosis
• Can neutralize toxins or block adhesion
• Can trigger complement system where blood
  proteins destroy invaders

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Cell-mediated immunity
Adaptive Immune System
T cells
T cell receptors recognize pathogen pieces
presented on infected cells

• Cytotoxic T cells Insert pores in infected
  cells, enzymes break down cells
• Helper T cells stimulate B cytotoxic T cell
  division
• Some T cells develop into memory cells

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Adaptive Immune System
Self-tolerance
MHC major histocompatibility complex
All cells have MHC molecules most body cells
have MHC I (lymphocytes have MHC II in
addition) MHC molecules displayed on cell
surface each binds a specific peptide foreign
fragment then displays it on surface.
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Adaptive Immune System
Self-tolerance
T-cells (cytotoxic or helper T) bind to MHC
presented antigens Self-reactive lymphocytes
with receptors to self epitopes are eliminated
before they leave bone marrow and mature
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Adaptive Immune System
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Adaptive Immune System
Immune system must remember past victories...

• Memory cells remember specific antigens
• May survive for years
• Respond faster and larger to repeat invasion

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Memory
Adaptive Immune System

• Memory B and T cells are able to recognize
  pathogens and fight off infections immediately

Then why do you keep catching a cold every year?
100 rhinoviruses Cold viruses can mutate
quickly
Vaccinations take advantage of the immune response
Body is exposed to antigens to stimulate memory
cells
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Antibiotics aid disease fight
Antibiotics

• Reduce growth and reproduction of living
  pathogens (not viruses)
• Give immune system time to fight infection
• Humans have misused antibiotics ?
  superbugs
• Overuse of antibacterial products
• Failure to complete full
  course of
  antibiotics
• Non-medicinal use of
  antibiotics

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Allergies
Immune System Problems

• Immune overreaction to harmless antigens
• Histamine triggers inflammation
• Extreme response can trigger anaphylaxis

Autoimmune Disorders
Immune system attacks healthy body cells Lupus,
Rheumatoid Arthritis, Multiple Sclerosis, Type 1
Diabetes, Celiac disease, Crohns disease
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Immune Deficiency Syndromes
Immune System Problems
Immune rejection
When tissue with non-self MHC molecules contact
immune system, response mounted Can be countered
by immunosuppressive drugs

• Severe Combined Immune Deficiency (SCID)
  Few/no immune cells produced ? genetic
• Acquired Immune Deficiency Syndrome (AIDS) Due
  to Human Immunodeficiency Virus (HIV)
• Destroys helper T cells

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Thought Question
What can you do to fortify your immune system?
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Things To Do After Lecture 13

• Reading and Preparation
• Re-read todays lecture, highlight all vocabulary
  you do not understand, and look up terms.
• Ch. 43 Self-Quiz 1 7 (correct answers in back
  of book)
• Read chapter 43, focus on material covered in
  lecture (terms, concepts, and figures!)
• Skim next lecture.

• HOMEWORK (NOT COLLECTED but things to think
  about for studying)
• Compare and contrast T cells and B cells, the
  humoral response compared to the cell-mediated
  immune response.
• Explain the function and parts of the human
  innate immune system.
• Describe the problem with each of the following
  allergies, autoimmune disorders, immune
  deficiency syndromes.
• Why are people concerned about over-use or misuse
  of antibiotics?