Immunology Lecture: Precipitation and Agglutination

Flashcards covering the core concepts of precipitation and agglutination, including antigen/antibody basics, soluble vs insoluble reactions, direct vs indirect methods, hemagglutination, and the roles of IgM and IgG.

What is an antigen?

A substance or molecule that is foreign to the body (non-self) and stimulates production of an antibody.

What is an antibody?

A glycoprotein produced by the immune system in response to an antigen; found in plasma/serum and body fluids; highly specific for its antigen.

How does the immune system distinguish self from non-self antigens?

Self antigens are recognized as part of the body and usually tolerated; non-self antigens trigger an immune response and antibody production.

What are some examples of antigens?

Toxins, bacteria, foreign blood cells, white blood cells, red blood cells, platelets, and antigens on transplanted organ cells.

How many antigens can be found on a single red blood cell?

Over 300 different antigens.

Where are antibodies located in the body?

In plasma and serum, as well as body fluids like tears and saliva.

What does antibody specificity mean?

Antibodies are specific for a particular antigen and bind primarily to that antigen (with possible cross-reactivity in some cases).

What is precipitation in immunology?

Formation of a visible insoluble complex when a soluble antigen reacts with an antibody.

What is agglutination in immunology?

Clumping or aggregation of insoluble particles (such as cells) caused by antibodies binding to antigens on their surface.

What is the key difference between precipitation and agglutination?

Precipitation involves soluble antigens; agglutination involves insoluble particles (cells or pathogens).

What is an agglutinin?

The antibody that causes agglutination and clumping of insoluble antigens.

Which antibody class is most effective for precipitation and agglutination?

IgM, a pentamer with 10 binding sites, is most effective in these reactions.

What is direct agglutination?

Agglutination where antigens are naturally present on the particles (cells) and react with antibodies without an extra step.

What is indirect (passive) agglutination?

Antigens are artificially placed on latex or charcoal particulates before reacting with antibodies.

What are particulates in indirect agglutination assays?

Latex or charcoal particles used as carriers for artificially placed antigens.

What is hemagglutination?

Agglutination that involves antigens on red blood cells; antibodies bind to those surface antigens.

Can you give an example of direct hemagglutination?

The test for mono (mononucleosis) is cited as an example of direct hemagglutination.

What is sensitization and lattice formation in agglutination?

Sensitization is the binding of an antibody to an antigen; lattice formation is the cross-linking that creates larger aggregates leading to visible clumping.