Affinity maturation

Where does somatic hypermutation occur?

Somatic hypermutation occurs within the germinal centers.

What drives somatic hypermutation?

The activity of activation-induced cytidine deaminase (AID) through cytosine-to-uracil transitions.

What does somatic hypermutation alter?

It alters the binding affinity of the original immunoglobulin on the B cell.

How does somatic hypermutation change the immunoglobulin's binding affinity?

Only if the deamination of cytosine bases and subsequent DNA repair mechanisms change the original cytosine base to another base.

Is the activity of AID towards cytosine bases predictable?

No, it is random toward cytosine bases in the variable regions of the immunoglobulin genes.

What effect can AID activity have on immunoglobulin affinity for its antigen?

The base changes can have a positive or negative effect on immunoglobulin affinity for its antigen.

What cells present antigens to centrocytes in the germinal center?

T cells, follicular dendritic cells, and macrophages.

What does the presentation of antigens to centrocytes promote?

It promotes additional rounds of positive and negative B-cell selection after somatic recombination has occurred.