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What Is Affinity Maturation?

Jennifer Long
Jennifer Long

Affinity maturation is an immune system response. This term describes the actions of a type of lymphocytes called B-cells and how they respond to antigen exposure. It is a process of cell variation and selection.

The immune system is responsible for protecting the body from foreign antigens. This is done by creating antibodies that attack and neutralize antigens before they can cause problems. Affinity maturation is the process that dictates the role that B-cells have in an immune system response.


B-cells lymphocytes are created in bone marrow. When a foreign antigen enters the body, B-cells are activated as they bind to the antigen. After binding, the cells now have two tasks. The first task in affinity maturation is to secrete antibodies that bind to the specific antigens. Through this action, the antigens are now tagged for removal through the innate system and its processes.

The second task in a B-cell’s affinity maturation is cloning, or to make copies. A B-cell that has completed the binding process must clone itself. Self-cloning often results in new cells that have different pathogen receptors than the parent cells. New cells can also bind to antigens, but only if the new cells are highly attracted to the antigens. These new cells continue the process by cloning themselves as the parent cells did.

When a B-cell, parent or cloned, has a high level of attraction toward an antigen, this is referred to as the cell’s affinity. B-cells with a higher affinity for an antigen are more likely to clone and have a stronger affinity. All of the B-cells compete to bind with the antigens that are available for binding. There will be some cells with stronger affinity levels than others, so these will clone more than others.

Through the whole process, affinity maturation is achieved when the cloned cells create new cells. Cell cloning provides a hyper-mutation so that each new generation of cells is more attracted to the antigen than the previous ones, which is the variation aspect. The selection aspect is evident in the stronger cells binding with the antigens instead of the weaker ones.

Higher pathogen response in B-cells is important when the exposure to antigens is continual or the antigens continue replicating themselves. B-cells and antigens posses the ability to reproduce and create new, stronger cells. Similar to the affinity maturation of B-cells, the antigen cells become stronger and more resilient with each new cell generation. It is a competition between the two cell types to determine which one is the strongest. In most instances, the immune system provides additional responses to invasion, giving the B-cells an added benefit.

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