Antibody specificity

1. Bind to a very specific molecule

2. The molecule they bind to is an antigen

3. Antibodies will be made against virtually any molecule, even molecules that have never existed

Antibody generation1. At birth, you have genes coding for thousands

of antibodies.

2. These will bind weakly to most antigens.

3. Following weak binding, antibodies are modified randomly, until more strongly binding antibodies are produced. This process is call affinity maturation

Antibody structure1. Y- shaped, with 2 binding sites

2. Therefore can aggregate cells, viruses, or other structures with more than one copy of an antigen

3. Antibodies have a variable region and a constant region. The binding sites are in the variable region.

A bacteria has multiple antigens

Binding sites

Antigens

Antibody A

Componentsof cell wall

Antibody B

Bacterial cell

Antibody subclasses

• IgG – most abundant• IgM – “immature” Ab, lower affinity• IgA – in secretions• IgE – responsible for allergies• IgD

Lymphocytes

1. There are 2 major types of lyphocytes: B lymphocytes and T lymphocytes

2. B lymphocytes make antibodies3. T lymphocytes have Ab-like molecules on

their cell membrane, which are the T-cell receptors