Antibodies and antigen

1. Antibodies are protective proteins produced by your immune system. They attach to antigens
(foreign substances) — such as bacteria, fungi, viruses and toxins — and remove them from your
body.
Antibodies are categorized into five classes according to their location. Each one is labeled by a
letter, which is attached to an abbreviation of the term “immunoglobulin” (Ig):
Antibody Type
IgA- Found in saliva, tears, mucus, breast milk and intestinal fluid, IgA protects against ingested and
inhaled pathogens.
IgD-This antibody is found on the surface of your B cells. Though its exact function is unclear, experts
think that IgD supports B cell maturation and activation.
IgE-Found mainly in the skin, lungs and mucus membranes, IgE antibodies cause your mast cells (a
type of white blood cell) to release histamine and other chemicals into your bloodstream. IgE
antibodies are helpful for fighting off allergic reactions.
IgG- This is the most common antibody, making up approximately 70% to 75% of all immunoglobulins
in your body. It’s found mainly in blood and tissue fluids. IgG antibodies help protect your body from
viral and bacterial infections.
IgM- Found in your blood and lymph system, IgM antibodies act as the first line of defense against
infections. They also play a large role in immune regulation.
Antibodies are part of a large family of chemicals called immunoglobulins, which play many
roles in the immune response:
Immunoglobulin G (IgG) marks microbes so other cells can recognize and deal with them
IgM specializes in killing bacteria
IgA congregates in fluids, such as tears and saliva, where it protects gateways into the body
IgE protects against parasites and plays a role in allergies
IgD stays bound to B lymphocytes, helping them start the immune response
Antibodies lock on to the antigen but do not kill it — they only mark it for death. The killing is the job of
other cells, such as phagocytes.
Classification of antigen
Depending on origin three types-
1.Exogenous antigens-entered the body from the outside, for example by inhalation, ingestion, or
injection (usually not virus)inhalation ingestion injection
2.Endogenous antigens-generated within normal cells (viral or intracellular bacterial infection)infection
3.Autoantigens (self-protein or complex of proteins (and sometimes self-DNA or RNA) )