Antibodies, monoclonal antibodies and vaccination

What is an antibody?

Proteins with specific binding sites synthesised by B cells which reacts with a specific, complementory antigen

Structure of an antibody

• four polypeptide chains

• the chains of one pair are long and called heavy chains

• chains of the other pair are shorter and called light chains

• has a specific binding site that fits with a specific antigen - antigen-antibody complex

• binding site is different on different antibodies so is called the variable region

• rest of antibody is known as constant region

How does an antibody lead to the destruction of an antigen

Antibodies do not destroy antigens directly but prepare antigen for destruction:

• cause agglutination of bacterial cells - clumps of bacterial cells are formed making it easier for phagocytes to locate them

• serve as markers that stimulates phagocytes to engulf the bacterial cells to which they are attached

Monoclonal antibodies

antibodies that are produced outside the body (in a lab)

Functions of monoclonal antibodies

• targeting medication to specific cell types by attaching a therapeutic drug to an antibody

• medical diagnosis

• pregnancy testing

Passive immunity

• produced by introduction of antibodies into individuals from an outside source

• immunity is acquired immediately

• no memory cells formed so no lasting immunity

• e.g. anti-venom given to victims of snake bites

Active immunity

Produced by stimulating the production of antibodies by the individuals’ own immune system so direct contact with the pathogen is necessary

• natural active immunity - results from an individual becoming infected with a disease under normal circumstances - body produces its own antibodies

• artificial active immunity - forms the basis of vaccination. involves inducing an immune response to an individual without them suffering the symptoms of the disease

What is vaccination?

The introduction of the appropriate disease antigens into the body, either by injection of by mouth to stimulate an immune response against a particular disease

• response is slight however memory cells are produced

• allow more immediate, greater response to a future infection with the pathogen

Herd immunity

arises when a sufficiently large proportion of the population has been vaccinated to make it difficult for a pathogen to spread within that population