Antibodies: structure, function, and immune response

Antibodies

List the five different kinds of antibodies and describe each of their functions.

An antibody is a protein used by the immune system to identify and neutralize invaders, such as bacteria and viruses. The term immunogloben is often used interchangeably with the term antibody. The first primary function of antibodies is to bind antigens. The second primary function is to combine with immunoglobulin receptors. The five classes of antibodies are IgG, IgA, IgM, IgD, and IgE.

IgG is the most common antibody in the human body. It is the only antibody which can pass through the placenta, so this is what provides fetuses with protection before they develop their own immune systems. IgG can bind to a wide range of pathogens.

IgA is found in the stomach, intestines, breast milk, tears, and saliva. IgA fights pathogens which contact the surface of the body, and pathogens which are swallowed or inhaled.

IgM antibodies are the first antibodies produced in response to primary exposure to pathogens that invade the body.

IgD is found on the surface of B-lymphocytes, and may play a role in suppressing spurious autoimmune responses.

IgE contains a lot of carbohydrates. It is found in connective tissue, as well as outer excretions. They are effective against many parasites, such as worms.

2. Describe what an autoimmune disease is.

Autoimmune diseases are from overactive immune responses, where the immune system attacks a person's own body instead of only attacking invading pathogens. There are over forty recognized autoimmune diseases. Women are more often affected by autoimmune diseases than men. Autoimmune diseases tend to share the symptom of fatigue, and often they appear during or just after puberty, so hormone levels may play a significant role.

3. Conduct independent Web research on autoimmune diseases. Choose one of them and describe which part of the immune system is compromised/defective.