How do B lymphocytes mature?
B lymphocytes are formed in the bone marrow from so-called blood stem cells (hematopoietic stem cells). These cells can still develop into all blood cells. However, in the course of development into fully mature cells (differentiation) they lose this ability.
Pro-B cells represent a further stage in the development of B lymphocytes. These then develop further into pre-B cells. They differ from B lymphocytes mainly in that they do not yet produce antibodies and cannot carry them on their surface.
Therefore, they do not yet have a receptor and cannot be activated. This is because the genes required for the production of antibodies cannot yet be read. Only after the genes have been rearranged are they released for reading.
This results in immature B-lymphocytes, which can only produce IgM antibodies. After they have become mature B-lymphocytes, they can also produce IgD antibodies. In this state they leave the bone marrow. They are still called naive because they had no contact with their antigen. Only after this contact they are activated and can now also produce the other antibody classes.
How are B lymphocytes activated?
There are two different ways in which B lymphocytes can be activated. In both cases, the antibody on the cell surface, which serves as a receptor, must have contact with its matching antigen. Learn more about superantigens.
In T-cell-independent activation, these B-cell receptors cross-link and activation occurs. However, this type of activation does not produce memory cells and only IgM class antibodies are produced. In T-cell-dependent activation, a T-cell with its receptor and signal molecules must interact with the B-cell.
This activation leads to the formation of memory cells and more types of antibodies can be produced. It is therefore considerably more effective. What is the function of T-lymphocytes? You can find the answer to this question under: T lymphocytes
Life span of a B-lymphocyte
The lifespan of B lymphocytes can vary greatly depending on whether the lymphocyte develops into a plasma cell or a memory cell. Plasma cells live only about 2-3 days. During this time, however, they divide very often, so that their cell clones take over their task after them.
Memory cells can remain in the body for decades or even a whole life. As long as they are alive, they are protected from the pathogen against which their antibodies are directed.