Positive selection in germinal centers

What do centrocytes do in positive selection in the germinal center?

They test the affinity of their immunoglobulins against antigens presented by follicular dendritic cells.

What happens to B cells with high-affinity immunoglobulins?

They gain survival signals (BAFF).

How do B cells with high-affinity immunoglobulins continue their activation?

They process and present bound antigen from the follicular dendritic cells to helper T cells.

What do helper T cells provide to B cells?

Survival signals and inhibit apoptosis through the expression of Bcl-XL.

What determines if a B cell survives in the germinal center?

B cells that interact with both follicular dendritic cells and helper T cells receive survival signals.

B cells with altered immunoglobulins that no longer interact with antigen die by apoptosis.

What must centrocytes have to successfully compete for survival signals?

The highest affinity for antigen.

What happens to centrocytes expressing higher affinity for antigen?

They differentiate into plasma cells that secrete higher affinity immunoglobulins.

What is the advantage of the long-term survival of plasma cells?

It is advantageous for future encounters with the same pathogen.

What other cell type can affinity maturation promote differentiation into?

Memory cells.