Immunity

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Immunity
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Defenses Against Disease
Lymph nodes makes lymphocytes.
White blood cells engulf microorganisms.
Cilia in respiratory tract sweep away debris.
Spleen filters out bacteria.
Stomach acid kills bacteria.
Skin acts as a barrier.
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Immunity

• The ability of the body to resist disease.
• First studied by Edward Jenner in 1776.
• He found that he could use fluid from a cowpox
  sore to vaccinate against smallpox (often fatal).

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How Immunity Works

• The body is able to tell the difference between
  self (its own cells and molecules) and
  nonself (foreign cells and molecules).

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How Immunity Works

• The reaction of the body to nonself cells is
  called the immune response.
• This involves destroying or neutralizing foreign
  cells or molecules with white blood cells and
  lymphatic tissue.

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The Immune Response

• Antigens cause the immune response to happen.
• Most antigens are proteins, but some are
  carbohydrates and nucleic acids.
• Most microorganisms and toxins contain antigens.

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The Immune Response

• Recognition and destruction of foreign antigens
  is the job of the lymphocytes.
• Lymphocytes are made in the bone marrow of the
  embryo and are stored in lymphoid tissue.

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Two Types of Lymphocytes (B T)

• Each lymphocyte has receptors for only one
  antigen.
• When the receptors recognize the antigen, the
  lymphocytes become activated.

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Activation of B Lymphocytes (BLs)

• When BLs are activated, they enlarge and divide
  repeatedly to form two different cell types
• 1. Plasma Cells
• 2. Memory Cells

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1. Plasma Cells

• Plasma cells secrete antibodies, which are
  proteins that react specifically with antigens
  and inactivate them.
• Antibodies have active sites that fit a
  compatible site on a certain antigen.

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Antigen-Antibody Reactions

• There are many different types of antibodies and
  they inactivate antigens in five different ways.

antigens
antibodies
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Antigen-Antibody Reactions

• 1. Agglutination Antigens are clumped together
  and thus inactivated.
• 2. Precipitation Antibodies form a complex with
  the antigens, and the complex settles out.

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Antigen-Antibody Reactions

• 3. Neutralization Antibodies combine with
  antigens, inactivating the toxic site of the
  antigen molecule.

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Antigen-Antibody Reactions

• 4. Lysis Antibodies cause the cell membranes of
  the antigenic microorganisms to burst.

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Antigen-Antibody Reactions

• 5. Complement System The complement system is a
  group of enzymes in the plasma. The
  antigen-antibody complex activates these
  enzymes, which attack the antigenic material.

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2. Memory Cells

• The memory cells stay in the lymphoid tissue.
• If the same antigen enters the body, the memory
  cells will immediately produce antibodies against
  it.

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Activation of T Lymphocytes (TLs)

• When TLs contact an antigen, they divide rapidly
  and make more TLS.Some stay in the lymphoid
  tissue as memory cells.
• Other TLs pass into the circulatory system and
  body tissues, where they combine with the
  antigens and destroy them.

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How Lymphocytes Make Antibodies

• Click here for animation.

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Types of Immunity

• Three main types of immunity
• 1. Inborn Immunity
• 2. Acquired Immunity
• 3. Passive Immunity

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1. Inborn Immunity

• Does not involve antibodies.
• Present in all humans from birth.
• Prevents humans from becoming infected with
  certain types of bacteria and viruses.
• Ex. Feline leukemia affects cats not humans.

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2. Acquired Immunity

• Two ways to get it
• 1. Contracting a disease-Ex. Chicken pox. Memory
  cells will,stay in the body and produce
  antibodies.
• 2. Vaccination-Vaccine serves to stimulate the
  production of specific antibodies to certain
  antigens.

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3. Passive Immunity

• Does not last long (about one month).
• Body destroys the borrowed antibodies.
• Fast acting.
• Found in babies who get antibodies via mothers
  milk.
• Helps protect child for a few months.