The process of immunological B-cell maturation involves transformation from an undifferentiated B cell to one that secretes antibodies with particular specificity. This differentiation and activation of the B cell occurs most rapidly after exposure to antigen by

antigen-presenting cell An antigen-presenting cell (APC) or accessory cell is a Cell (biology), cell that displays an antigen bound by major histocompatibility complex (MHC) proteins on its surface; this process is known as antigen presentation. T cells may recognize the ...

s in the reticuloendothelial system, and under modulation by

T cell T cells (also known as T lymphocytes) are an important part of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell ...

s, and is closely intertwined with affinity maturation. B cells that respond most avidly to antigen are preferentially allowed to proliferate and mature, a process known as

clonal selection In immunology, clonal selection theory explains the functions of cells of the immune system (lymphocytes) in response to specific antigens invading the body. The concept was introduced by Australian doctor Frank Macfarlane Burnet in 1957, in an ...

. In lymphocytic neoplastic diseases such as

multiple myeloma Multiple myeloma (MM), also known as plasma cell myeloma and simply myeloma, is a cancer of plasma cells, a type of white blood cell that normally produces antibody, antibodies. Often, no symptoms are noticed initially. As it progresses, bone ...

and

lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). The name typically refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlarged lymph node ...

, but also other illnesses, there can be a massive expansion of a single B-cell clone, detectable by measuring the excessively-produced antibodies, measured in a serum protein electrophoresis test or peripheral blood

flow cytometry Flow cytometry (FC) is a technique used to detect and measure the physical and chemical characteristics of a population of cells or particles. In this process, a sample containing cells or particles is suspended in a fluid and injected into the ...

. Such an expansion is said to be "monoclonal", and

monoclonal antibodies A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a Lineage (evolution), cell lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell. Mon ...

produced by such a group of B cells can cause illnesses such as amyloidosis and lupus, or can be indicative of an underlying

malignancy Malignancy () is the tendency of a medical condition to become progressively worse; the term is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not ...

. The concept of clonality is closely associated with

, for example in diagnosing lymphomatoid

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

lesions. The expansion of a particular clone of immune B cells is usually interpreted by clinicians as evidence of unrestricted cell growth, the hallmark of

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

Footnotes

{{reflist Lymphocytes

See also

Footnotes