Immune System II

1
Immune System II

• Acquired Immunity

2
Immunity

• There are four attributes characteristic of
  immunity
• Specific cells of the immune system recognize
  specific pathogens not others. (Inflammation is a
  nonspecific response)
• Memory once the immune system has been exposed
  to a certain pathogen and has developed defenses
  against the organism, it can attack the pathogen
  over and over and more quickly when it reappears.

3
Immunity

• Diversity the immune system is able to attack
  thousands of foreign microbes including bacteria,
  viruses, parasitic worms and fungi.
• Self - Nonself recognition the immune system can
  distinguish between body cells and cells that
  have invaded the body.

4
Recognition

• How does the immune system recognize molecules?
• The immune system produces two distinct responses
  to invading organisms
• Production of antibodies (proteins that mark
  foreign molecules)
• Production of cells that recognize and attack
  infected body cells.

5
Specificity

• Antibodies are proteins that bind to nonself
  molecules which are called antigens
• Each antibody recognizes a specific shape and
  charge of an antigen.

6
Immune Cells

• Immune cells are a special class of white blood
  cells called lymphocytes and develop in the lymph
  tissue.
• The 3 main classes of lymphocytes are
• B lymphocytes (B cells) which make antibodies
  that recognize bacteria, fungi and protists marks
  them but does not kill them.

7
Immune Cells

• T lymphocytes (T cells), which recognize and
  destroy infected or damaged body cells.
• Natural Killer Cells (NK cells), attack tumor
  cells and cells infected by a pathogen

8
Antibodies

• Each line of B cells makes just one kind of
  antibody.
• Every antigen contains one or more epitopes ( a
  specific shape and charge)that the antibody
  recognizes
• All antibodies are globular proteins called
  immunoglobulins.

9
Antibodies

• Immunoglobulins are made of a collection of four
  amino acid chains, two heavy chains and two light
  chains.
• There are 5 classes of immunoglobulins. They all
  have the same light chains and differ by their
  heavy chains.

10
Antibodies

• Antibodies have at least two binding sites,
  allowing them to bind to more than one antigen.
  This allows them to link together bacteria, the
  clumped mass is a better target for phagocytes to
  attack.

11
5 Types of Antibodies
12
Antibodies

• IgG and IgM activate compliment proteins, which
  destroy marked cells
• IgM molecules are the first to appear after
  exposure to an antigen, while IgG are made in
  greater amounts in secondary responses.

13
Antibodies

• IgA molecules protect all of the bodys surfaces
  (intestinal respiratory and urogenital tracts)
  are in tears, saliva, and breast milk

14
Antibodies

• IgE antibodies probably evolved to defend the
  body against parasitic worms however many people
  produce IgE antibodies in response to harmless
  antigens.
• Allergy - a response to a harmless antigen like
  dust mites, pollen, shell fish

15
(No Transcript)
16
Antibodies

• When one of these antigens enters the respiratory
  tract, IgE molecules attach to mast cells, which
  release histamine.
• Inflammatory response is triggered, mucus
  secretions, contraction of airways
• Extreme response can end in death

17
B-Cells

• B cells are lymphocytes that are formed in bone
  marrow. Each B cell has B cell receptors (BCR)
  on its surface. These receptors recognize the
  same antigen sites as the antibodies it produces.

18

• When an antigen binds to B cell receptors, the B
  cell begins to differentiate
• Some become plasma cells, which make antibodies
• Some become memory cells, which make more B cells
  for when the antigen reappears

19
Differentiation of B cells
Memory B cells Make more memory cells
Antigen
Plasma Cells Make antibodies
B cells
20
Memory

• Second exposure to the antigen will cause a rapid
  and very strong response due to memory cells
• Multiplication of memory cells provides a
  lifelong immunity
• B cells cannot respond to body cells that have
  become infected with pathogens

21

• B cells produce antibodies that can recognize
  bacteria and target them for destruction.
• But B cells do not respond to the bodys own
  cells that have become infected or are cancerous.

22
Vaccinations

• Because lymphocytes respond to epitopes (shape
  and charge of proteins on the surface of
  antigens) rather than the whole molecules
  antigens whose epitopes are identical can cause
  an immune response for each other.

23
T cells

• T cells recognize body cells that are infected or
  are growing out of control.
• A child born without a thymus, where T-cells
  mature, cannot fight viral, fungal and
  intracellular bacterial infections.
• The child may have plenty of B cells and can
  fight some bacterial infections.

24
T cells

• Two kinds of T cells
• T cytotoxic (killing cells by boring holes in the
  cell membrane) TC cells. Kill cancerous and
  infected
• T helper or TH cells alert B cells to make
  antibodies and stimulate TC cells. Produce
  cytokines

25
T Cells MHC Proteins

• T cells recognize the cells of the body by
  proteins called major histocompatability complex
  or MHC.
• MHC proteins are on every cell of the body except
  sperm cells.
• Everyones set of MHCs are unique
• Transplant surgeons make sure transplant organs
  have similar MHCs to the patient.

26
MHC Proteins

• MHC Class 1 are on every cell with a nucleus
  except sperm.
• MHC Class 2 are on the surface of macrophages and
  dendritic cells.

27
(No Transcript)