Adaptive immunity II: Antibodies

Question 1

Antibody

Answer 1

A protein that binds specifically to a particular molecule- its antigen. Each antibody has a unique variable region (made by gene recombination) that enables it to bind specifically. They are known collectively as immunoglobulins. They are produced by differentiated B cells – Plasma cells and are the secreted form of the BCR.

Question 2

Somatic Hypermutation

Answer 2

Mutations in variable region of rearranged DNA of heavy and light chain genes due to conversion of cytosine to uracil

Question 3

Class switching

Answer 3

The gene recombination process found in activated B cells that replaces the heavy chain constant region from μ which gives IgM with another of different isotype i.e. changing the antibody from IgM to the production of IgG, IgA or IgE. This affects their function but not the antigen specificity

Question 4

Antigen

Answer 4

Any molecule that can bind specifically to an antibody or generate peptide fragments that are recognised by TCR of T cells

Question 5

Neutralisation

Answer 5

Inhibition of infection by viruses or the toxicity of toxin molecules secreted by infectious organisms by the binding of antibody

Question 6

Fc Fragment, Fc Region

Answer 6

The COOH halves of the two heavy chains of an antibody produced by cleavage by papain. In the complete antibody, this portion is called the Fc region

Question 7

Fab Fragment

Answer 7

Antibody fragment composed of a single antigen binding site of an antibody without the Fc region. It is produced by cleavage of antibody with papain. It consists of a complete light chain and the NH2 terminal of the heavy chain composed of the variable region and the first constant region held together by a disulphide bond