Question

What do T cells acquire from the thymus that makes them able to work with B cells together in the immune response?

Answer 1

T cell production

T cells start out as stem  cells (early types of cells that have not yet fully grown) and are produced by bone  marrow.

To mature, these stem cells move to the thymus, where they can stay for up to three weeks. About 99% of T cells do not make it to maturity. This is because the body is very selective about what T cells are produced so that they do not cause damage to the body’s own cells.

In the thymus, the T cells are given T cell receptors, of which there are several types. The type of receptor received determines what type of T cell it will be, what its role is, and which cells it can interact with.

T cell function

T cells function both through the release of substances into the blood, and by signalling B cells through contact. They have several different roles:

• Signalling for growth and activation of B cells

• Activation of cells that can ‘eat’ foreign substances

• Stimulation of cytotoxic T cells during a viral infection

• Signalling growth in cells, including other T cells, macrophages and eosinophils .

B cell activation

The majority of B cell activation takes place in the lymph  nodes. Certain types of cells in the lymph nodes eat anything foreign and present them to B and T cells. Any B cell that shares a receptor for this substance will be activated and start to multiply. B cells can also be activated by helper T cells. After activation, active B cells migrate around the body and change into plasma cells.

Plasma cells

Plasma cells are B cells that remain committed to the production and secretion of a single antibody type. This secretion gives rise to the antibodies found in the circulation. Immunity is kept for as long as the plasma cell continues to secrete antibodies.