What Are B Cells?

There are two major types of lymphocytes: B-cells and T-cells.

B-cells, also known as B lymphocytes, are one of several types of white blood cells in the body that are produced in the bone marrow through a process called hematopoiesis, which is the formation and development of both red and white blood cells.

B-cells roam the body as part of our immune system, protecting us from foreign antigens that pose a threat to our health.

Why the letter B?

B-cells get their name not from research done into human anatomy but from research done into the anatomy of birds. But 'birds' isn't the origin of the B; instead, B-cells were named after the site in birds where this specific type of blood cell matures, called the bursa of Fabricius. Fortunately, in humans and many other mammals B-cells mature in the bone marrow, allowing the B to continue to make sense.

To that end, T-cells get their letter designation from the site where they mature too; in this case, it is the thymus.

The role of B-cells

Once they mature, B-cells leave the bone marrow and begin to circulate throughout the body by way of the blood and lymphatic system, or they might hang around in any one of the many lymphoid organs (thymus, lymph nodes, spleen).

B-cells are distinct from other cells in the immune system by their display of membrane-bound immunoglobin molecules. This means that on the surface of a single B-cell there are thousands of molecules of antibody, and they all have an identical binding site for antigen.

When that specific binding site on the cell meets the antigen that matches it, it kicks in an adaptive immune response to this threat: the B-cell begins to divide very quickly. In doing so, it creates two types of daughter cells: plasma cells and memory B cells, both of which have a separate function in the immune system.