1. Antibodies
A membrane attack complex (MAC) forms as a result of activation of
the complement
cascade.
The MAC
results in
lysis of the cell.

2. Antibodies There are 5 classes of antibodies:
IgG – a monomer with two antigen-binding sites
Comprises 80% of total antibody
Only class able to cross the placenta
Provides long-term immunity
IgM – a pentamer with ten antigen-binding sites
It is a great activator of complement, but has a short-lived response.
It is the first antibody to appear in an immune response

3. Antibodies Classes of Antibodies
IgA – a dimer with four antigen-binding sites
prevalent in body secretions like sweat, tears, saliva, breast milk and gastrointestinal fluids
IgE – a monomer involved in allergic reactions
comprises less than 0.1% of total antibody in the blood
IgD – a monomer with a wide array of functions, some of which have been a puzzle since its discovery in 1964

4. Antibodies
Classes of Antibodies

5. Antibodies
Thousands of memory cells exist after initial encounter with an antigen - this is called Immunological Memory.
With the next appearance of the same antigen, memory cells can proliferate and differentiate within hours.
This graphic shows that
serum antibody titers
are much higher and
much faster on the
second response

6. Gaining Immunocompetence
Within the framework of innate and adaptive immunity we have discussed, there are a number of designations for the ways we can become immunocompetent:
“Natural Immunity” is not gained through the tools of modern medicine, whereas ”Artificial Immunity” is.
Active Immunity refers to the body’s response to make antibody after exposure to a pathogen (antigen).
In Passive Immunity, the body simply receives antibodies that have been preformed.
Active immunity is long-term; passive is short-term.

7. Gaining Immunocompetence
Examples
Natural active – contracting hepatitis A and production of anti-hepatitis A antibodies
Natural passive - a baby receives antibodies from its mother through the placenta and breast milk.
Artificial active - a person receives a vaccine of an attenuated (changed/weakened) pathogen that stimulates the body to form an antibody.
Artificial passive – an injection of prepared antibody

8. Immunological Surveillance
A current theory purports that the formation of cancer cells is a common occurrence in all of us, and that the immune system continually recognizes and removes them.
There are a number of well-recognized tumor antigens which are displayed on certain cancerous cells.
These cells are targeted for destruction by cytotoxic T cells, macrophages and natural killer cells.
Most effective in eliminating tumor cells due to cancer-causing viruses

9. The Immune System and Aging
Atrophy of the thymus gland results in decreased T-helper cell populations, and a diminished mediation of the specific-immune response.
There is a resulting decreased B-cell response and decreased number of T-cytotoxic cells.
Compromised immune function with age results in increased titers of autoantibodies and an increased incidence of cancer (both contribute to overall mortality rates.)

10. End of Chapter 22
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