Download Aseptic Technique: Media and Equipment

MICROBIOLOGY – ALCAMO
LECTURE:
Specific Immune
System
B Cells
&
T Cells
Specific Immune System
• Late 1800’s:
– not sure how body responded to disease
– knew there were certain proteins in blood
involved (Bence Jones proteins)
• 1922:
– these proteins were unlike other serum
proteins
Specific Immune System
• 1950’s:
– post-war explosion in biological research
– realized that specific resistance applied to
disease, organ transplant, allergies,
resistance to cancer
• 1960’s:
– structure of antibodies deciphered
– maturing of immunology as a key scientific
discipline
Specific Immune System
•
Last defense mechanism of the body
–
failure to beat the invader means death
•
“Man to Man” defense against invaders
•
Specific immune system cells:
–
Only Lymphocytes – type of WBC
Antigens
• Substances capable of mobilizing the
immune system and provoking immune
responses
• Large complex molecules not normally
present in the body
• They are anything non-self: Mo’s,
Cells, Cells containing MO’s, or
chemicals
• Epitope – small area of antigen that
stimulates the immune response
Antigens
• Exhibit 2 important properties:
– Immunogenicity – ability to stimulate the
proliferation of the immune system cells
– Reactivity – ability to react with the
products of the immune system cells or
the immune system cells themselves
Antigens
• Specific Immunologic Tolerance –
before birth, the proteins and
polysaccharides of the body contact
and inactivate immune system cells
• These substances are now seen as
“self” and will be tolerated by immune
system
Origins of Immune System
• General term for a complex series of
cells, factors, and processes that
provide a specific response to antigens
• Lymphocytes – the cornerstone of the
immune system:
– Spread throughout the body
– Small cells (10-20 um) with a large nucleus
– Can be B-lymphocytes or T-lymphocytes
Origins of Immune System
• Immune system arises in a fetus ~ 2
months after conception
• Lymphocytes arise from precursor
cells in the bone marrow (stem cells)
• Stem cells can be:
– Erythropoietic – become RBC’s
– Lymphopoietic – become WBC’s
T Lymphocytes
Original cells from bone marrow
•
Memory programmed in thymus gland
•
Circulate in blood, colonize lymph tissue
•
Interact directly with antigen marked
cells and destroy them
•
Antigens: Infected body
cells, fungi, protozoa,
cancer, transplants
T Lymphocytes
2 “T” cell types (total 4 “T” Cells)
– Effector “T” Cells:
•
Killer T - worker
•
Delayed Sensitivity T allergies
– Regulator “T” Cells:
•
•
Helper T – don’t kill
•
Suppressor T – lower immune response
Active chemical: Lymphokines ( a
group of glycoproteins)
T Lymphocytes
Process
•
Phagocytic cell finds antigen in tissue
(cell’s surface looks different if infected)
•
Brings it to lymph tissue containing
memory cells (spleen or lymph node)
•
May remember antigen
•
If “Yes”
•
If “No”
•
Cell mediated Immunity (CMI)
T Lymphocytes
If “Yes”
•
Clones 2 Cell Types
•
Memory T Cells and
•
Killer T which makes lymphokines
•
Lymphokines kill or inactivate
antigens and stimulate
phagocytosis
Back
T Lymphocytes
If “NO”
•
In thymus, program
blank T cells for
antigen memory
•
To lymph tissue in
nearest war zone
•
Now: Clone Memory
T and Killer T
Back
B Lymphocytes
Profile
•
Original cells from bone marrow
•
Memory programmed in bone marrow
•
Circulate in blood and
colonize lymph tissue
•
Antigens: Bacteria,
Viruses, Chemicals
•
Active chemical:
Antibody
B Lymphocytes
Process
•
Phagocytic cell finds antigen in blood
•
Brings it to lymph tissue containing
memory B cells
•
May remember antigen from before
–
We all have 1,000s of memory B cells
•
If “YES”
•
IF “NO”
B Lymphocytes
• If “Yes”:
– Clones 2 cell types
– Memory B cell (so it won’t
forget) and plasma cell to
make antibodies (2,000
molecules/sec/cell 4-5 days)
– Antibodies kill or inactivate antigen and
stimulate phagocytosis
Back
B Lymphocytes
• If “No”:
– Blank B cells in bone marrow program
for antigen memory to lymph tissue
nearest “war zone”
– Now clone memory and plasma cells
Back
B Lymphocytes
Process (continued)
•
Antibodies: Stimulate complement
proteins to attack
•
Monocytes and macrophages clean up
•
Antibody Mediated Immunity (AMI)
Antibodies
• Edelman and Porter described the
structure of antibodies (1972)
• Basic Antibody Protein:
• Has 4 polypeptide chains
– 2 identical heavy chains (400 AA)
– 2 identical light chains (200 AA)
– Joined together by disulfide bonds to form
a “Y” shaped structure
• Is called a monomer and has 2 identical
halves (1 heavy and 1 light chain each)
Antibodies
• Have constant and variable regions
• Constant regions – identical in all
antibodies (AB)
• Variable regions – differ among 100’s
of thousands of different AB
– Form a very specific, 3-D structure
– Uniquely shaped to “fit” a specific antigen
– Each arm can bind an antigen
Types of antibodies
• Five Types – based on differences in
heavy chain:
– 1. IgM – five monomers joined to form a
pentamer, First AB to appear after
stimulation of B-cells
– 2. IgG – monomer, the major AB in the
blood that appears 24-48 hrs after antigen
appears, provides long-term resistance,
crosses placenta to give immunity to fetus
Types of antibodies
• Five Types – based on differences in
heavy chain:
– 3. IgA – dimer shaped AB that accumulates
in body secretions in respiratory and GI
tracts, in tears and saliva, and in the 1st
milk secreted by a nursing mother
– 4. IgE – monomer that is involved in
allergic reactions
– 5. IgD – monomer – function unknown
Antigen antibody Interaction
• Neutralizing AB’s – react with viral
capsids and prevent entry into cells
• Antitoxins – alter toxin molecules
released by antigen
• Agglutinins – cause clumping of
antigens and enhances phagocytosis
• Precipitins – react with dissolved
antigens and convert them to solids