Immune System

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Immune System

• Pre-AP Biology
• Chapter 40-2

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Immune System Overview

• Function fight infection through the production
  of specialized cells that inactivate foreign
  substances or cells
• It is main defense against pathogens
• Recognizes, attacks, destroys, and remembers
  each type of pathogen that enters the body
• 2 general categories
• Nonspecific defenses (fortress walls of the body)
• Specific defenses (security guards of the body)

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Nonspecific Defenses

• First line of defense skin
• Most important nonspecific defense!
• Very few pathogens can penetrate the skin
• Must have an opening a cut, scratch, mouth,
  nose
• Mucus, saliva, and tears have lysozyme enzyme
  that breaks down bacterias cell wall
• Oil and sweat glands produce acidic environment
• Mucus and cilia in nose and throat trap and push
  pathogens away from lungs
• Acid and enzymes destroy bacteria that make it to
  your stomach

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Nonspecific Defenses

• Second line of defense inflammatory response
• Reaction to tissue damage caused by
  injury/infection
• When pathogens are detected
• White blood cells flood area through blood
  vessels near wound
• Many WBC are phagocytes engulf and destroy
• Releases chemicals that increase core body
  temperature (fever)
• Many pathogens only survive in narrow temp. range
• Increased temp also increases heart rate more
  WBC

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Nonspecific Defense to Viruses

• Sometimes, virus-infected cells produce a group
  of proteins that help other cells resist
  infection Interferons
• Named this because they interfere with growth
  of the virus
• Slows the progress of infection and gives
  specific defense system time to respond

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Specific Defenses

• Called immune response
• Triggered by antigens
• 2 types of lymphocytes
• B lymphocytes (B cells) work in body fluids
• Humoral immunity
• T lymphocytes (T cells) work in living cells
• Cell-mediated immunity

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Humoral Immunity

• B cells detect pathogen and multiply rapidly
• Produces large numbers of plasma cells and memory
  B cells
• Plasma cells release antibodies (proteins that
  recognize and bind to antigens recall blood
  types!)
• Antibodies carried in the blood stream to attack
• Memory B cells remain capable of producing
  antibodies specific to that pathogen after
  exposure

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Antibody Structure

• Antibody is shaped like a Y and has two
  identical antigen binding sites
• Differences in amino acids affect shape of
  binding sites
• Shape of binding site is how antibody recognizes
  antigen
• Healthy adult can produce about 100 million
  different types of antibodies!

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Cell-Mediated Immunity

• Primary defense against own cells when cancerous
  or infected
• Also important for fighting fungi and protists
• Process T cells divide and differentiate into
• Killer T cells destroy bacteria, fungi,
  protozoan or foreign tissue with the antigen
• Helper T cells produce memory T cells
• Suppressor T cells shut down killer T cells
  after pathogenic cells brought under control
• Memory T cells cause response if same antigen
  enters again

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Transplants

• Killer T cells make organ transplants difficult
• Recognize new organ as foreign and attack it
• Called rejection
• To prevent rejection, donor should have cell
  markers nearly identical to recipient and
• Recipient usually takes drugs for the rest of
  their life to suppress cell-mediated immune
  response.

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Acquired Immunity

• Remember Jenners smallpox??
• Cowpox infection to create immunity to smallpox
• Can be active or passive

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Active vs. Passive Immunity

• Active

• Passive

• Type of immunity produced by reaction to a
  vaccine
• Vaccination injection of weakened or mild form
  of pathogen
• Stimulate immune system to create plasma cells
• Plasma cells are ready to make specific
  antibodies
• Appears AFTER exposure
• Can be natural or deliberate

• Antibodies produced by other animals injected
  into the bloodstream
• Lasts for short time body eventually destroys
  them
• Can be natural or deliberate
• Natural from mother to fetus or in breastmilk
• Deliberate vaccine
• Tropical diseases
• Rabies