B lymphocytes

Definition

B lymphocytes, or B cells, are a type of white blood cell that play a vital role in the adaptive immune response by producing antibodies against specific antigens. They originate from hematopoietic stem cells in the bone marrow and mature there before migrating to peripheral tissues. Upon encountering an antigen, B cells can differentiate into plasma cells, which produce large amounts of antibodies, or memory B cells that provide long-lasting immunity.

5 Must Know Facts For Your Next Test

1. B lymphocytes have surface receptors called B cell receptors (BCRs) that specifically recognize and bind to antigens.
2. Upon activation by an antigen, B cells undergo clonal expansion, rapidly dividing to produce many identical cells that can produce the same antibody.
3. Memory B cells can persist for years after the initial infection and respond more quickly upon re-exposure to the same antigen.
4. The process of somatic hypermutation allows B cells to enhance the affinity of their antibodies for a specific antigen during an immune response.
5. B lymphocytes also play a role in activating T lymphocytes by presenting antigens through their major histocompatibility complex (MHC) molecules.

Review Questions

• How do B lymphocytes recognize and respond to specific antigens?
  • B lymphocytes recognize specific antigens through their unique B cell receptors (BCRs), which are membrane-bound immunoglobulins. When a B cell encounters its specific antigen, it binds to it, leading to activation. This activation triggers clonal expansion, where the B cell proliferates and differentiates into plasma cells that produce antibodies or memory B cells for future responses.
• Discuss the importance of memory B cells in providing long-term immunity.
  • Memory B cells are crucial for long-term immunity because they remain in the body after the initial infection has resolved. When re-exposed to the same antigen, these cells can quickly proliferate and differentiate into antibody-producing plasma cells. This rapid response leads to a more effective and efficient defense against pathogens, highlighting the importance of vaccination in enhancing memory B cell formation.
• Evaluate the role of B lymphocytes in the overall adaptive immune response and their interaction with T lymphocytes.
  • B lymphocytes play a central role in the adaptive immune response by producing antibodies that target specific antigens. Their interaction with T lymphocytes is essential for a coordinated immune response. Activated B cells can present processed antigens on their MHC molecules to helper T cells, which provide necessary signals for full activation of the B cells. This collaboration enhances the effectiveness of both B and T cell responses against infections.

Related terms

Antibodies: Proteins produced by plasma cells that specifically bind to antigens, neutralizing pathogens or marking them for destruction by other immune cells.

T lymphocytes: A type of white blood cell that plays a crucial role in cell-mediated immunity, helping to regulate the immune response and directly kill infected or cancerous cells.

Antigen-presenting cells: Cells that process and present antigens to T lymphocytes, crucial for initiating the adaptive immune response; examples include dendritic cells and macrophages.