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

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

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

Antibodies Classes of Antibodies

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

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.

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

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

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.)

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